BACKGROUND Gastric cancer(GC)has become a serious threat to people's health.Accumulative evidence reveals that dysregulation of numerous microRNAs(miRNAs)has been found during malignant formation.So far,the role o...BACKGROUND Gastric cancer(GC)has become a serious threat to people's health.Accumulative evidence reveals that dysregulation of numerous microRNAs(miRNAs)has been found during malignant formation.So far,the role of microRNA-760(miR-760)in the development of GC is largely unknown.AIM To measure the expression level of miR-760 in GC and investigate its role in gastric tumorigenesis.METHODS Real-time quantitative polymerase chain reaction and Western blot analysis were used to measure the expression of miR-760 and G-protein-coupled receptor kinase interacting protein-1(GIT1).Cell growth was detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide(MTT)and cell colony formation assays.Apoptosis was assessed by flow cytometric analysis.The relationship between miR-760 and GIT1 was verified by luciferase reporter assay.RESULTS The results showed that the expression of miR-760 was decreased in GC and associated with poor clinical outcomes in GC patients.Furthermore,miR-760 restrained cell proliferation and cell colony formation and induced apoptosis in GC cells.In addition,miR-760 directly targeted GIT1 and negatively regulated its expression in GC.GIT1 was upregulated in GC and predicted a worse prognosis in GC patients.We also found that upregulation of GIT1 weakened the inhibitory CONCLUSION In conclusion,miR-760 targets GIT1 to inhibit cell growth and promote apoptosis in GC cells.Our data demonstrate that miR-760 may be a potential target for the treatment of GC.展开更多
AIM: To clarify the associations between G-protein beta polypeptide 3 (GNB3) C825T polymorphism and risk of the irritable bowel syndrome (IBS) by a meta-analysis.
The heterotrimeric GTP-binding proteins（G-proteins） in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors（GPCR）, on which to tra...The heterotrimeric GTP-binding proteins（G-proteins） in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors（GPCR）, on which to transduce signaling into the cytoplast through appropriate downstream effectors. However, downstream effectors regulated by the G-proteins in plants are currently not well defined. In this study, the transcripts of AGB1, a G protein β subunit gene in Arabidopsis were found to be down-regulated by cold and heat, but up-regulated by high salt stress treatment. AGB1 mutant（agb1-2） was more sensitive to high salt stress than wild-type（WT）. Compared with WT, the cotyledon greening rates, fresh weight, root length, seedling germination rates and survival rates decreased more rapidly in agb1-2 along with increasing concentrations of Na Cl in normal（MS） medium. Physiological characteristic analysis showed that compared to WT, the contents of chlorophyll, relative proline accumulation and peroxidase（POD） were reduced, whereas the malonaldehyde（MDA） content and concentration ratio of Na＋/K＋ were increased in agb1-2 under salt stress condition. Further studies on the expression of several stress inducible genes associated with above physiological processes were investigated, and the results revealed that the expressions of genes related to proline biosynthesis, oxidative stress response, Na＋ homeostasis, stress- and ABAresponses were lower in agb1-2 than in WT, suggesting that those genes are possible downstream genes of AGB1 and that their changed expression plays an important role in determining phenotypic and physiologic traits in agb1-2. Taken together, these findings indicate that AGB1 positively regulates salt tolerance in Arabidopsis through its modulation of genes transcription related to proline biosynthesis, oxidative stress, ion homeostasis, stress- and ABA-responses.展开更多
Insufficient sleep has been correlated to many physiological and psychoneurological disorders.Over the years,our understanding of the state of sleep has transcended from an inactive period of rest to a more active sta...Insufficient sleep has been correlated to many physiological and psychoneurological disorders.Over the years,our understanding of the state of sleep has transcended from an inactive period of rest to a more active state involving important cellular and molecular processes.In addition,during sleep,electrophysiological changes also occur in pathways in specific regions of the mammalian central nervous system(CNS).Activity mediated synaptic plasticity in the CNS can lead to long-term and sometimes permanent strengthening and/or weakening synaptic strength affecting neuronal network behaviour.Memory consolidation and learning that take place during sleep cycles,can be affected by changes in synaptic plasticity during sleep disturbances.G-protein coupled receptors(GPCRs),with their versatile structural and functional attributes,can regulate synaptic plasticity in CNS and hence,may be potentially affected in sleep deprived conditions.In this review,we aim to discuss important functional changes that can take place in the CNS during sleep and sleep deprivation and how changes in GPCRs can lead to potential problems with therapeutics with pharmacological interventions.展开更多
Anti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides ...Anti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides that are expressed in the colonic epithelia. This study investigated the effect and the signaling mechanism of inducible β-defensin HBD2 by an essential amino acid, isoleucine (Ile) in colonic epithelial cells. Here we examined the expression level of HBD2 on induction of Ile in epithelial cells, and checked this pathway. HBD2 mRNA was induced by co-incubation with IL-1α and Ile in Caco2 cells, but not by Ile alone. An inhibitor of either ERK or Gi, a subunit of G-proteins, reduced the induction of HBD2 mRNA by Ile. The treatment with Ile also increased the intracellular calcium ion concentration, thus suggesting that the GPCR and ERK signaling pathway mediate the effects of Ile. These results indicate that an essential amino acid, Ile, enhances the expression of an inducible β-defensin, namely HBD2, by IL-1α through the activation of GPCRs and ERK signaling pathway. The administration of Ile may therefore represent a possible option to safely treat intestinal inflammation.展开更多
BACKGROUND： The prevalences of hypertension, cerebrovascular diseases, etc. are higher in Mongolian population because of the influence of various factors including genetics, geography, diet, etc. Therefore, it is he...BACKGROUND： The prevalences of hypertension, cerebrovascular diseases, etc. are higher in Mongolian population because of the influence of various factors including genetics, geography, diet, etc. Therefore, it is helpful for prevention to develop researches on the genetics of various diseases including hypertension in Mongolian population. OBJECTIVE： To analyze the association between C825T polymorphisms of G-protein beta 3 subunit gene （GNB3）, the important candidate gene of various disease of cardiovascular system, and Mongolian patients with essential hypertension. DESIGN： A comparative observation. SETTINGS： Department of Neurology, the First Affiliated Hospital of Inner Mongolia Medical College; Wulate Houqi Red Cross Society. PARTICIPANTS： Totally 267 Mongolian residents, whose blood relations of 3 generations were all Mongolians, were selected from Wulate Houqi, Inner Mongolia. The patients were screened based on the diagnostic standard of hypertension set by WHO in 1999, and the enrolled subjects were divided into two groups according to the level of blood pressure： ① Normal blood pressure group （n =124）： 64 males and 60 females, systolic blood pressure （SBP） 〈 140 mm Hg （1 mm Hg=0.133 kPa）, diastolic blood pressure （DBP） 〈 90 mm Hg;②Essential hypertension group （n =143）： 71 males and 72 females, including 60 patients with simple high SBP （SBP ranged 145 to 195 mm Hg, whereas DBP 〈 90 mm Hg）. METHODS： Peripheral venous blood （5 mL） was drawn from all the subjects, the genome DNA was extracted, and the polymorphisms of the GNB3 C825T genotype were detected with the Sequenom system. Polyrnerase chain reaction （PCR） experiment and SNP detection were performed in Beijing Huada gene laboratory. Then the univariate analysis of variance was applied in the sample comparison among groups, and the chi-square test was used to compare the genotypes and allele frequencies. The odd ratio （OR） and 95% confidence interval （CI） were calculated. MAIN OUTCOME MEASURES： The distributions of GNB3 C825T genotypes and alleles were observed. RESULTS： All the 267 Mongolian subjects were involved in the analysis of results.① GNB3 C825T genotypes： In Mongolian population, the frequencies of CC, CT and TT genotypes at GNB3 C825T site in the essential hypertension group （48%, 41%, 11%） were not obvious different from those in the normal blood pressure group （43%, 47%, 10%, x^2 =0.162, P =0.688; OR：1.176, 95%CI： 0.533- 2.592）, whereas there were also no obvious differences between the simple high SBP group （57%, 35%, 8%） and the normal blood pressure group （x^2 =0.733, P =0.392; OR：1.957, 95%CI： 0.623- 6.143）. ②GNB3 C825T alleles： In Mongolian population, The frequencies of C and T alleles in the essential hypertension group （69%, 31%） were not obviously different from those in the normal blood pressure group （67%, 33%, x^2 =0.094, P = 0.759; OR：0.945, 95%CI：0.657 - 1.358）, whereas there were also no obvious differences between the simple high SBP group （74%, 26%） and the normal blood pressure group （ x^2 =2.133, P =0.144; OR：0.697, 95%CI： 0.428- 1.133）. CONCLUSION： GNB3 C825T site may be not a genetic marker of essential hypertension and simple high SBP in Mongolian population.展开更多
BACKGROUND: The increased β-arrestin-2 and its combination with G-protein-coupled receptors (GPCRs) lead to GPCRs desensitization. The latter may be responsible for decreased contractile reactivity in the mesenteric ...BACKGROUND: The increased β-arrestin-2 and its combination with G-protein-coupled receptors (GPCRs) lead to GPCRs desensitization. The latter may be responsible for decreased contractile reactivity in the mesenteric arteries of cirrhotic patients and rats. The present study is to investigate the machinery changes of α-adrenergic receptors and G proteins and their roles in the contractility of mesenteric arteries of cirrhotic patients and animal models. METHODS: Patients with cirrhosis due to hepatitis B and cirrhotic rats induced by CCl 4 were studied. Mesenteric artery contractility in response to norepinephrine was determined by a vessel perfusion system. The contractile effect of G protein-coupled receptor kinase-2 (GRK-2) inhibitor on the mesenteric artery was evaluated. The protein expression of the α 1 adrenergic receptor, G proteins, β-arrestin-2, GRK-2 as well as the activity of Rho associated coiled-coil forming protein kinase-1 (ROCK-1) were measured by Western blot. In addition, the interaction of α 1 adrenergic receptor with β-arrestin-2 was assessed by co-immunoprecipitation. RESULTS: The portal vein pressure of cirrhotic patients and rats was significantly higher than that of controls. The doseresponse curve to norepinephrine in mesenteric arteriole was shifted to the right, and EC 50 was significantly increased in cirrhotic patients and rats. There were no significant differences in the expressions of the α 1 adrenergic receptor and G proteins in the cirrhotic group compared with the controls. However, the protein expressions of GRK-2 and β-arrestin-2 were significantly elevated in cirrhotic patients and rats compared with those of the controls. The interaction of the α 1 adrenergic receptor and β-arrestin-2 was significantly aggravated. This interaction was significantly reversed by GRK-2 inhibitor. Both the protein expression and activity of ROCK-1 were significantly decreased in the mesenteric artery in patients with cirrhosis compared with those of the controls, and this phenomenon was not shown in the cirrhotic rats. Norepinephrine significantly increased the activity of ROCK-1 in normal rats but not in cirrhotic ones. Norepinephrine significantly increased ROCK-1 activity in cirrhotic rats when GRK-2 inhibitor was used. CONCLUSIONS: β-arrestin-2 expression and its interaction with GPCRs are significantly upregulated in the mesenteric arteries in patients and rats with cirrhosis. These upregulations result in GPCR desensitization, G-protein dysfunction and ROCK inhibition. These may explain the decreased contractility of the mesenteric artery in response to vasoconstrictors.展开更多
The renal handling of Na^(+) balance is a major determinant of the blood pressure(BP) level. The inability of the kidney to excrete the daily load of Na+ represents the primary cause of chronic hypertension. Among the...The renal handling of Na^(+) balance is a major determinant of the blood pressure(BP) level. The inability of the kidney to excrete the daily load of Na+ represents the primary cause of chronic hypertension. Among the different segments that constitute the nephron, those present in the distal part(i.e., the cortical thick ascending limb, the distal convoluted tubule, the connecting and collecting tubules) play a central role in the fine-tuning of renal Na^(+) excretion and are the target of many different regulatory processes that modulate Na^+ retention more or less efficiently. G-protein coupled receptors(GPCRs) are crucially involved in this regulation and could represent efficient pharmacological targets to control BP levels. In this review, we describe both classical and novel GPCR-dependent regulatory systems that have been shown to modulate renal Na^(+) absorption in the distal nephron. In addition to the multiplicity of the GPCR that regulate Na^(+) excretion, this review also highlights the complexity of these different pathways, and the connections between them.展开更多
In the last few years, there have been important new insights into the structural biology of G-protein coupled receptors. It is now known that allosteric binding sites are involved in the affinity and selec- tivity of...In the last few years, there have been important new insights into the structural biology of G-protein coupled receptors. It is now known that allosteric binding sites are involved in the affinity and selec- tivity of ligands for G-protein coupled receptors, and that signaling by these receptors involves both G-protein dependent and independent pathways. The present review outlines the physiological and pharmacological implications of this perspective for the design of new drugs to treat disorders of the central nervous system. Specifically, new possibilities are explored in relation to allosteric and or- thosteric binding sites on dopamine receptors for the treatment of Parkinson＇s disease, and on muscarinic receptors for Alzheimer＇s disease. Future research can seek to identify ligands that can bind to more than one site on the same receptor, or simultaneously bind to two receptors and form a dimer. For example, the design of bivalent drugs that can reach homo/hetero-dimers of D2 dopa- mine receptor holds promise as a relevant therapeutic strategy for Parkinson＇s disease. Regarding the treatment of Alzheimer＇s disease, the design of dualsteric ligands for mono-oligomeric mus- carinic receptors could increase therapeutic effectiveness by generating potent compounds that could activate more than one signaling pathway.展开更多
Cochliobolus heterostrophus is an agriculturally important and emerging model pathogen for studying the signaling hierarchies' role during the maize host colonization. In particular, G-protein and MAPK-linked path...Cochliobolus heterostrophus is an agriculturally important and emerging model pathogen for studying the signaling hierarchies' role during the maize host colonization. In particular, G-protein and MAPK-linked pathways are playing a major role during pathogenesis. Although gene disruption studies are an efficient way of identifying the role of these cascades, differentiating between the mutant strains’ virulence ability may become an intricate task. For example, in C. heterostrophus, mutants in a G-protein α subunit gene, cga1, are defective in mating and appressorium formation, but unlike mutants in homologous genes in other fungal pathogens, the cga1 mutants remained highly virulent to corn under some host physiological conditions. Here, we used the cga1 strain as a model for developing an in vivo sensitive and accurate pathogenicity assay. A detailed and well controlled analysis of wild type (WT) and cga1 pathogenic behavior revealed that detached leaves are significantly more vulnerable to the disease than intact ones. In intact leaves, cga1 mutants were less infective of maize under most conditions. This difference was maximized when the first seedling leaf was chosen for inoculation and when the infected leaves, with spores or mycelia fragments droplets, were incubated for a period of four days. This optimal condition set enabled us to classify the C. heterostrophus G-protein signaling mutants deficient in α, β or both subunits in order of decreasing virulence: WT > cga1> cgb1> cga1 cgb1. The method presented proved to be accurate and sensitive enough to identify even slight variations in virulence. Moreover, it could be modified for use in studies of other foliar phytoparasitic fungi.展开更多
AIM To investigate whether GNB3 C825 T single nucleotide polymorphism(SNP)contributes to systolic blood pressure(SBP)≥130 mmH g in a large-scale cross-sectional study among the Japanese population with diastolic bloo...AIM To investigate whether GNB3 C825 T single nucleotide polymorphism(SNP)contributes to systolic blood pressure(SBP)≥130 mmH g in a large-scale cross-sectional study among the Japanese population with diastolic blood pressure(DBP)<85 mmH g.METHODS We analyzed 11008 Japanese subjects,including 2797 cases(SBP≥130 and DBP<85 mmH g)who were not taking anti-hypertensive medication and 8211 controls(SBP<130 and DBP<85 mmH g),all of whom enrolled in the genome banking project of the 21 st Century COE(Center of Excellence)Program at Jichi Medical University.Subjects were divided into four groups according to gender(male and female)and age(≤49 years and≥50 years).GNB3 gene polymorphism was determined using the TaqM an probe method.We compared the frequencies of alleles and genotypes between cases and controls by chi-squared test.The strength of the associations was estimated by odds ratios(ORs)and 95%CI by using logistic regression analysis.The ORs were adjusted for age and body mass index.RESULTS Allele and genotype distributions significantly differed between cases and controls only in males aged≤49 years.Compared to the CC genotype,a significant OR was obtained in the TT genotype among males aged≤49 years.CONCLUSION This study indicates that the TT genotype of the GNB3 C825 T SNP may contribute to SBP elevation of greater than 130 mmH g compared to the CC genotype in Japanese males aged≤49 years.展开更多
Bisphenol A(BPA) is one of the highest volume industrial products worldwide and has been widely used to make various products as the intermediates of polycarbonate plastics and epoxy resins.Inevitably, general populat...Bisphenol A(BPA) is one of the highest volume industrial products worldwide and has been widely used to make various products as the intermediates of polycarbonate plastics and epoxy resins.Inevitably, general population has been widely exposed to BPA due to extensive use of BPAcontaining products. BPA has similar chemical structure with the natural estrogen and has been shown to induce a variety of estrogen-like endocrine effects on organism in vivo or in vitro. High doses of BPA tend to act as antagonist of estrogen receptors(ERs) by directly regulating the genomic transcription. However, BPA at environmentally relevant low-dose always disrupt the biological function via a non-genomic manner mediated by membrane receptors, rather than ERs. Although some studies had investigated the non-genomic effects of low-dose BPA, the exact molecular mechanism still remains unclear. Recently, we found that membrane G protein-coupled estrogen receptor 1 and integrin αvβ3 and its relative signal pathways participate in the induction of male germ cell proliferation and thyroid transcription disruption by the low-dose BPA. A profound understanding for the mechanism of action of the environmentally relevant BPA exposure not only contributes to objectively evaluate and predict the potential influence to human health, but also provides theoretical basis and methodological support for assessing health effects trigged by other estrogen-like environmental endocrine disruptors. Based mainly on our recent findings, this review outlines the research progress of molecular mechanism on endocrine disrupting effects of environmental low-dose BPA, existing problems and some consideration for future studies.展开更多
Heterotrimeric G-proteins,comprising Gα,Gβ,and Gγsubunits,act as crucial molecular switches for signaling transduction in all eukaryotic organisms.Through precise modulation of specific receptors or effectors coupl...Heterotrimeric G-proteins,comprising Gα,Gβ,and Gγsubunits,act as crucial molecular switches for signaling transduction in all eukaryotic organisms.Through precise modulation of specific receptors or effectors coupled with heterotrimeric G-proteins in signaling cascades,plants have the capability to activate or suppress unique signaling pathways necessary for plant growth,development,and stress responses.This review provides an overview of the heterotrimeric G-proteins signaling pathway obtained to date,and highlights novel areas for future exploration and agricultural application based on the emerging significance and potential of heterotrimeric G proteins in regulating plant development and responses to abiotic stress.展开更多
Heterotrimeric G proteins are crucial transducers of signaling from receptors,participating in growth and development,as well as in responses to biotic and abiotic stimuli.However,little is known about their roles in ...Heterotrimeric G proteins are crucial transducers of signaling from receptors,participating in growth and development,as well as in responses to biotic and abiotic stimuli.However,little is known about their roles in regulating various yield-related traits in legumes.In this study,we systematically analyzed the functions of two G-protein-encoding genes,MtGα1 and MtGβ1,along with Regulator of G-protein Signaling1(MtRGS1),in Medicago truncatula.All three genes were ubiquitously expressed in roots,stems,leaves,nodules,flowers,and pods.We generated the knockout mutants Mtgα1,Mtgβ1,and Mtrgs1 using CRISPR/Cas9 and assessed their growth and development.MtGα1 knockout resulted in slightly shorter plants with smaller pods and shorter spines,but larger seeds,without affecting overall biomass or other traits.MtGβ1 knockout led to dwarfism,weak root development,a severe drop in biomass production,smaller legume pods with shorter spines,and smaller seeds.However,the Mtrgs1 mutants were largely similar to wild-type plants,with few significant defects in growth and development.We also investigated the symbiotic nodulation-related phenotypes of these mutants,discovering that Mtgβ1 mutants produce lighter nodules,whereas Mtgα1 and Mtrgs1 mutants have normal nodulation phenotypes similar to those of wild-type plants.These observations suggest that MtGβ1 positively regulates nodulation,although the detailed mechanisms by which G proteins regulate symbiotic nitrogen fixation in M.truncatula remain to be explored.This work provides potentially valuable genetic resources for further functional analysis and elucidation of the molecular mechanisms of G proteins in this model legume.展开更多
Heterotrimeric GTP-binding proteins, which consist of Gα, Gβ, and Gγ subunits, play important roles in transducing extracellular signals perceived by cell surface receptors into intracellular physiological response...Heterotrimeric GTP-binding proteins, which consist of Gα, Gβ, and Gγ subunits, play important roles in transducing extracellular signals perceived by cell surface receptors into intracellular physiological responses. In addition to a single prototypical Gα protein （GPA1）, Arabidopsis has three unique Gα-Iike proteins, known as XLG1, XLG2, and XLG3, that have been found to be localized in nuclei, although their functions and mode of action remain largely unknown. Through a transcriptomic analysis, we found that XLG2 and XLG3 were rapidly induced by infection with the bacterial pathogen Pseudomonas syringae, whereas the XLG1 transcript level was not affected by pathogen infection. A reverse genetic screen revealed that the xlg2 loss-of-function mutation causes enhanced susceptibility to P. syringae. Transcriptome profiling revealed that the xlg2 mutation affects pathogen-triggered induction of a small set of defense-related genes. However, xlgl and xlg3 mutants showed no difference from wild-type plants in resistance to P. syringae, In addition, the xlg2 xlg3 double mutant and the xlgl xlg2 xlg3 triple mutant were not significantly different from the xlg2 single mutant in the disease resistance phenotype, suggesting that the roles of XLG1 and XLG3 in defense, if any, are less significant than for XLG2. Constitutive overexpression of XLG2 leads to the accumulation of abnormal transcripts from multiple defense-related genes. Through co-immunoprecipitation assays, XLG2 was found to interact with AGB1, the sole Gβ subunit in Arabidopsis, which has previously been found to be a positive regulator in resistance to necrotrophic fungal pathogens. However, no significant difference was found between three xlg single mutants, the xlg2 xlg3 double mutant, the xlgtriple mutant, and wild-type plants in resistance to the necrotrophic fungal pathogens Botrytis cinerea or Alternaria brassicicola. These results suggest that XLG2 and AGB1 are components of a G-protein complex different from the prototypical heterotrimeric G-protein and may have distinct functions in modulating defense responses.展开更多
Light and the heterotrimeric G-protein are known to antagonistically regulate photomorphogenesis in Arabidopsis. However, whether light and G-protein coordinate the regulation of photomorphogenesis is largely unknown....Light and the heterotrimeric G-protein are known to antagonistically regulate photomorphogenesis in Arabidopsis. However, whether light and G-protein coordinate the regulation of photomorphogenesis is largely unknown. Here we show that the blue light photoreceptor cryptochrome 1 （CRY1） physically inter-acts with the G-protein β subunit, AGB1, in a blue light-dependent manner. We also show that AGB1 directly interacts with HY5, a basic leucine zipper transcriptional factor that acts as a critical positive regulator of photomorphogenesis, to inhibit its DNA-binding activity. Genetic studies suggest that CRY1 acts partially through AGB1, and AGB1 acts partially through HY5 to regulate photomorphogenesis. Moreover, we demonstrate that blue light-triggered interaction of CRY1 with AGB1 promotes the dissociation of HY5 from AGB1. Our results suggest that the CRY1 signaling mechanism involves positive regulation of the DNA-binding activity of HY5 mediated by the CRY1-AGB1 interaction, which inhibits the association of AGB1 with HY5. We propose that the antagonistic regulation of HY5 DNA-binding activity by CRY1 and AGB1 may allow plants to balance light and G-protein signaling and optimize photomorphogenesis.展开更多
Hypocotyl development in Arabidopsis thaliana is regulated by light and endogenous hormonal cues, mak- ing it an ideal model to study the interplay between light and endogenous growth regulators. BBX21, a B-box （BBX...Hypocotyl development in Arabidopsis thaliana is regulated by light and endogenous hormonal cues, mak- ing it an ideal model to study the interplay between light and endogenous growth regulators. BBX21, a B-box （BBX）-Iike zinc-finger transcription factor, integrates light and abscisic acid signals to regulate hypocotyl elongation in Arabidopsis. Heterotrimeric G-proteins are pivotal regulators of plant development. The short hypocotyl phenotype of the G-protein I^-subunit （AGB1） mutant （agbl-2） has been previously identified, but the precise role of AGB1 in hypocotyl elongation remains enigmatic. Here, we show that AGB1 directly interacts with BBX21, and the short hypocotyl phenotype of agbl-2 is partially suppressed in agb1-2bbx21-1 double mutant. BBX21 functions in the downstream of AGB1 and overexpression of BBX21 in agbl-2 causes a more pronounced reduction in hypocotyl length, indicating that AGB1 plays an oppositional role in relation to BBX21 during hypocotyl development. Furthermore, we demonstrate that the C-terminal region of BBX21 is important for both its intracellular localization and its transcriptional activation activity that is inhibited by interaction with AGB1. ChiP assays showed that BBX21 specifically associates with its own promoter and with those of BBX22, HY5, and GA2oxl. which is not altered in agbl-2. These data suggest that the AGB1-BBX21 interaction only affects the transcrip- tional activation activity of BBX21 but has no effect on its DNA binding ability. Taken together, our data demonstrate that AGB1 positively promotes hypocotyl elongation through repressing BBX21 activity.展开更多
The Arabidopsis heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi. The agbl mutant impaired in the Gβ subunit displays enhanced susceptibility to these pathogens. Gβ/AGB1 forms a...The Arabidopsis heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi. The agbl mutant impaired in the Gβ subunit displays enhanced susceptibility to these pathogens. Gβ/AGB1 forms an obligate dimer with either one of the Arabidopsis Gγsubunits （γ1/AGG1 and γ2/AGG2）. Accordingly, we now demonstrate that the aggl agg2 double mutant is as susceptible as agbl plants to the necrotrophic fungus Plectosphaerella cucumerina. To elucidate the molecular basis of heterotrimeric G-protein-mediated resistance, we performed a comparative transcriptomic analysis of agbl-1 mutant and wild-type plants upon inoculation with P cucumerina. This analysis, together with metab- olomic studies, demonstrated that G-protein-mediated resistance was independent of defensive pathways required for resistance to necrotrophic fungi, such as the salicylic acid, jasmonic acid, ethylene, abscisic acid, and tryptophan-derived metabolites signaling, as these pathways were not impaired in agbl and aggl agg2 mutants. Notably, many mis-reguiated genes in agbl plants were related with cell wall functions, which was also the case in aggl agg2 mutant. Biochemical analyses and Fourier Transform InfraRed （FTIR） spectroscopy of cell walls from G-protein mutants revealed that the xylose content was lower in agbl and aggl agg2 mutants than in wild-type plants, and that mutant walls had similar FTIR spec-tratypes, which differed from that of wild-type plants. The data presented here suggest a canonical functionality of the Gβ and Gγ1/γ2 subunits in the control of Arabidopsis immune responses and the regulation of cell wall composition.展开更多
Background： G-protein β-polypeptide 3 （GNB3） is a β subunit isoform of G-protein that plays important role in signal transduction of membrane G-protein coupled receptors （GPCRs）. The GNB3 splice variant C825T ...Background： G-protein β-polypeptide 3 （GNB3） is a β subunit isoform of G-protein that plays important role in signal transduction of membrane G-protein coupled receptors （GPCRs）. The GNB3 splice variant C825T （rs5443） is associated with risk for essential hypertension （EH） and efficacy of therapeutic drugs targeting GPCRs. It is unknown whether the polymorphism is associated with blood pressure （BP） response to telmisartan or amlodipine, two widely prescribed antihypertensive drugs. Methods： A total of 93 subjects initially diagnosed as EH were recruited and underwent a 4-week treatment with telmisartan （42 patients） or amlodipine （51 patients） monotherapy. Both baseline and after-treatment BP were measured. GNB3 C825T polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism. Results： Baseline systolic BP （SBP） and diastolic BP （DBP） were comparable among C825T genotypes in both telmisartan and amlodipine treatment groups. Patients with the CT or TT genotypes showed significantly lower body mass index （BMI） as compared with CC homozygotes in both groups （P 〈 0.05, respectively）. GNB3 825TT homozygotes showed significantly higher alier-treatment DBP and mean arterial presstire （MAP） than those carrying at least one 825C allele （P 〈 0.01） in the telmisartan treatment group. No difference in after-treatment SBE DBP, and MAP levels among C825T genotypes was observed in the amlodipine treatment group. No significant difference in absolute changes in BP levels was observed among the genotypes in either treatment group. Conchlsion： The GNB3 C825T splice variant is associated with the DBP-lowering effect of telmisartan but not amlodipine in Chinese EH patients.展开更多
文摘BACKGROUND Gastric cancer(GC)has become a serious threat to people's health.Accumulative evidence reveals that dysregulation of numerous microRNAs(miRNAs)has been found during malignant formation.So far,the role of microRNA-760(miR-760)in the development of GC is largely unknown.AIM To measure the expression level of miR-760 in GC and investigate its role in gastric tumorigenesis.METHODS Real-time quantitative polymerase chain reaction and Western blot analysis were used to measure the expression of miR-760 and G-protein-coupled receptor kinase interacting protein-1(GIT1).Cell growth was detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide(MTT)and cell colony formation assays.Apoptosis was assessed by flow cytometric analysis.The relationship between miR-760 and GIT1 was verified by luciferase reporter assay.RESULTS The results showed that the expression of miR-760 was decreased in GC and associated with poor clinical outcomes in GC patients.Furthermore,miR-760 restrained cell proliferation and cell colony formation and induced apoptosis in GC cells.In addition,miR-760 directly targeted GIT1 and negatively regulated its expression in GC.GIT1 was upregulated in GC and predicted a worse prognosis in GC patients.We also found that upregulation of GIT1 weakened the inhibitory CONCLUSION In conclusion,miR-760 targets GIT1 to inhibit cell growth and promote apoptosis in GC cells.Our data demonstrate that miR-760 may be a potential target for the treatment of GC.
文摘AIM: To clarify the associations between G-protein beta polypeptide 3 (GNB3) C825T polymorphism and risk of the irritable bowel syndrome (IBS) by a meta-analysis.
基金funded in part by the National Key Project for Research on Transgenic Biology(2013ZX08002-002)the National Natural Science Foundation of China (31201200)
文摘The heterotrimeric GTP-binding proteins（G-proteins） in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors（GPCR）, on which to transduce signaling into the cytoplast through appropriate downstream effectors. However, downstream effectors regulated by the G-proteins in plants are currently not well defined. In this study, the transcripts of AGB1, a G protein β subunit gene in Arabidopsis were found to be down-regulated by cold and heat, but up-regulated by high salt stress treatment. AGB1 mutant（agb1-2） was more sensitive to high salt stress than wild-type（WT）. Compared with WT, the cotyledon greening rates, fresh weight, root length, seedling germination rates and survival rates decreased more rapidly in agb1-2 along with increasing concentrations of Na Cl in normal（MS） medium. Physiological characteristic analysis showed that compared to WT, the contents of chlorophyll, relative proline accumulation and peroxidase（POD） were reduced, whereas the malonaldehyde（MDA） content and concentration ratio of Na＋/K＋ were increased in agb1-2 under salt stress condition. Further studies on the expression of several stress inducible genes associated with above physiological processes were investigated, and the results revealed that the expressions of genes related to proline biosynthesis, oxidative stress response, Na＋ homeostasis, stress- and ABAresponses were lower in agb1-2 than in WT, suggesting that those genes are possible downstream genes of AGB1 and that their changed expression plays an important role in determining phenotypic and physiologic traits in agb1-2. Taken together, these findings indicate that AGB1 positively regulates salt tolerance in Arabidopsis through its modulation of genes transcription related to proline biosynthesis, oxidative stress, ion homeostasis, stress- and ABA-responses.
基金Supported by Canadian Institutes of Health Research Grant,No.TGS-1092194-Year Fellowship from the University of British Columbia.
文摘Insufficient sleep has been correlated to many physiological and psychoneurological disorders.Over the years,our understanding of the state of sleep has transcended from an inactive period of rest to a more active state involving important cellular and molecular processes.In addition,during sleep,electrophysiological changes also occur in pathways in specific regions of the mammalian central nervous system(CNS).Activity mediated synaptic plasticity in the CNS can lead to long-term and sometimes permanent strengthening and/or weakening synaptic strength affecting neuronal network behaviour.Memory consolidation and learning that take place during sleep cycles,can be affected by changes in synaptic plasticity during sleep disturbances.G-protein coupled receptors(GPCRs),with their versatile structural and functional attributes,can regulate synaptic plasticity in CNS and hence,may be potentially affected in sleep deprived conditions.In this review,we aim to discuss important functional changes that can take place in the CNS during sleep and sleep deprivation and how changes in GPCRs can lead to potential problems with therapeutics with pharmacological interventions.
文摘Anti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides that are expressed in the colonic epithelia. This study investigated the effect and the signaling mechanism of inducible β-defensin HBD2 by an essential amino acid, isoleucine (Ile) in colonic epithelial cells. Here we examined the expression level of HBD2 on induction of Ile in epithelial cells, and checked this pathway. HBD2 mRNA was induced by co-incubation with IL-1α and Ile in Caco2 cells, but not by Ile alone. An inhibitor of either ERK or Gi, a subunit of G-proteins, reduced the induction of HBD2 mRNA by Ile. The treatment with Ile also increased the intracellular calcium ion concentration, thus suggesting that the GPCR and ERK signaling pathway mediate the effects of Ile. These results indicate that an essential amino acid, Ile, enhances the expression of an inducible β-defensin, namely HBD2, by IL-1α through the activation of GPCRs and ERK signaling pathway. The administration of Ile may therefore represent a possible option to safely treat intestinal inflammation.
基金a grant from the Great Program of Inner Mongolia Medical College, No. NY2004ZD006
文摘BACKGROUND： The prevalences of hypertension, cerebrovascular diseases, etc. are higher in Mongolian population because of the influence of various factors including genetics, geography, diet, etc. Therefore, it is helpful for prevention to develop researches on the genetics of various diseases including hypertension in Mongolian population. OBJECTIVE： To analyze the association between C825T polymorphisms of G-protein beta 3 subunit gene （GNB3）, the important candidate gene of various disease of cardiovascular system, and Mongolian patients with essential hypertension. DESIGN： A comparative observation. SETTINGS： Department of Neurology, the First Affiliated Hospital of Inner Mongolia Medical College; Wulate Houqi Red Cross Society. PARTICIPANTS： Totally 267 Mongolian residents, whose blood relations of 3 generations were all Mongolians, were selected from Wulate Houqi, Inner Mongolia. The patients were screened based on the diagnostic standard of hypertension set by WHO in 1999, and the enrolled subjects were divided into two groups according to the level of blood pressure： ① Normal blood pressure group （n =124）： 64 males and 60 females, systolic blood pressure （SBP） 〈 140 mm Hg （1 mm Hg=0.133 kPa）, diastolic blood pressure （DBP） 〈 90 mm Hg;②Essential hypertension group （n =143）： 71 males and 72 females, including 60 patients with simple high SBP （SBP ranged 145 to 195 mm Hg, whereas DBP 〈 90 mm Hg）. METHODS： Peripheral venous blood （5 mL） was drawn from all the subjects, the genome DNA was extracted, and the polymorphisms of the GNB3 C825T genotype were detected with the Sequenom system. Polyrnerase chain reaction （PCR） experiment and SNP detection were performed in Beijing Huada gene laboratory. Then the univariate analysis of variance was applied in the sample comparison among groups, and the chi-square test was used to compare the genotypes and allele frequencies. The odd ratio （OR） and 95% confidence interval （CI） were calculated. MAIN OUTCOME MEASURES： The distributions of GNB3 C825T genotypes and alleles were observed. RESULTS： All the 267 Mongolian subjects were involved in the analysis of results.① GNB3 C825T genotypes： In Mongolian population, the frequencies of CC, CT and TT genotypes at GNB3 C825T site in the essential hypertension group （48%, 41%, 11%） were not obvious different from those in the normal blood pressure group （43%, 47%, 10%, x^2 =0.162, P =0.688; OR：1.176, 95%CI： 0.533- 2.592）, whereas there were also no obvious differences between the simple high SBP group （57%, 35%, 8%） and the normal blood pressure group （x^2 =0.733, P =0.392; OR：1.957, 95%CI： 0.623- 6.143）. ②GNB3 C825T alleles： In Mongolian population, The frequencies of C and T alleles in the essential hypertension group （69%, 31%） were not obviously different from those in the normal blood pressure group （67%, 33%, x^2 =0.094, P = 0.759; OR：0.945, 95%CI：0.657 - 1.358）, whereas there were also no obvious differences between the simple high SBP group （74%, 26%） and the normal blood pressure group （ x^2 =2.133, P =0.144; OR：0.697, 95%CI： 0.428- 1.133）. CONCLUSION： GNB3 C825T site may be not a genetic marker of essential hypertension and simple high SBP in Mongolian population.
基金supported by a grant from the National Natural Science Foundation of China (30972920)
文摘BACKGROUND: The increased β-arrestin-2 and its combination with G-protein-coupled receptors (GPCRs) lead to GPCRs desensitization. The latter may be responsible for decreased contractile reactivity in the mesenteric arteries of cirrhotic patients and rats. The present study is to investigate the machinery changes of α-adrenergic receptors and G proteins and their roles in the contractility of mesenteric arteries of cirrhotic patients and animal models. METHODS: Patients with cirrhosis due to hepatitis B and cirrhotic rats induced by CCl 4 were studied. Mesenteric artery contractility in response to norepinephrine was determined by a vessel perfusion system. The contractile effect of G protein-coupled receptor kinase-2 (GRK-2) inhibitor on the mesenteric artery was evaluated. The protein expression of the α 1 adrenergic receptor, G proteins, β-arrestin-2, GRK-2 as well as the activity of Rho associated coiled-coil forming protein kinase-1 (ROCK-1) were measured by Western blot. In addition, the interaction of α 1 adrenergic receptor with β-arrestin-2 was assessed by co-immunoprecipitation. RESULTS: The portal vein pressure of cirrhotic patients and rats was significantly higher than that of controls. The doseresponse curve to norepinephrine in mesenteric arteriole was shifted to the right, and EC 50 was significantly increased in cirrhotic patients and rats. There were no significant differences in the expressions of the α 1 adrenergic receptor and G proteins in the cirrhotic group compared with the controls. However, the protein expressions of GRK-2 and β-arrestin-2 were significantly elevated in cirrhotic patients and rats compared with those of the controls. The interaction of the α 1 adrenergic receptor and β-arrestin-2 was significantly aggravated. This interaction was significantly reversed by GRK-2 inhibitor. Both the protein expression and activity of ROCK-1 were significantly decreased in the mesenteric artery in patients with cirrhosis compared with those of the controls, and this phenomenon was not shown in the cirrhotic rats. Norepinephrine significantly increased the activity of ROCK-1 in normal rats but not in cirrhotic ones. Norepinephrine significantly increased ROCK-1 activity in cirrhotic rats when GRK-2 inhibitor was used. CONCLUSIONS: β-arrestin-2 expression and its interaction with GPCRs are significantly upregulated in the mesenteric arteries in patients and rats with cirrhosis. These upregulations result in GPCR desensitization, G-protein dysfunction and ROCK inhibition. These may explain the decreased contractility of the mesenteric artery in response to vasoconstrictors.
文摘The renal handling of Na^(+) balance is a major determinant of the blood pressure(BP) level. The inability of the kidney to excrete the daily load of Na+ represents the primary cause of chronic hypertension. Among the different segments that constitute the nephron, those present in the distal part(i.e., the cortical thick ascending limb, the distal convoluted tubule, the connecting and collecting tubules) play a central role in the fine-tuning of renal Na^(+) excretion and are the target of many different regulatory processes that modulate Na^+ retention more or less efficiently. G-protein coupled receptors(GPCRs) are crucially involved in this regulation and could represent efficient pharmacological targets to control BP levels. In this review, we describe both classical and novel GPCR-dependent regulatory systems that have been shown to modulate renal Na^(+) absorption in the distal nephron. In addition to the multiplicity of the GPCR that regulate Na^(+) excretion, this review also highlights the complexity of these different pathways, and the connections between them.
基金supported by SIP-IPN,CONACYT (CB-168116)FIS/IMSS (FIS/IMSS/PROT/G11-2/1013)
文摘In the last few years, there have been important new insights into the structural biology of G-protein coupled receptors. It is now known that allosteric binding sites are involved in the affinity and selec- tivity of ligands for G-protein coupled receptors, and that signaling by these receptors involves both G-protein dependent and independent pathways. The present review outlines the physiological and pharmacological implications of this perspective for the design of new drugs to treat disorders of the central nervous system. Specifically, new possibilities are explored in relation to allosteric and or- thosteric binding sites on dopamine receptors for the treatment of Parkinson＇s disease, and on muscarinic receptors for Alzheimer＇s disease. Future research can seek to identify ligands that can bind to more than one site on the same receptor, or simultaneously bind to two receptors and form a dimer. For example, the design of bivalent drugs that can reach homo/hetero-dimers of D2 dopa- mine receptor holds promise as a relevant therapeutic strategy for Parkinson＇s disease. Regarding the treatment of Alzheimer＇s disease, the design of dualsteric ligands for mono-oligomeric mus- carinic receptors could increase therapeutic effectiveness by generating potent compounds that could activate more than one signaling pathway.
文摘Cochliobolus heterostrophus is an agriculturally important and emerging model pathogen for studying the signaling hierarchies' role during the maize host colonization. In particular, G-protein and MAPK-linked pathways are playing a major role during pathogenesis. Although gene disruption studies are an efficient way of identifying the role of these cascades, differentiating between the mutant strains’ virulence ability may become an intricate task. For example, in C. heterostrophus, mutants in a G-protein α subunit gene, cga1, are defective in mating and appressorium formation, but unlike mutants in homologous genes in other fungal pathogens, the cga1 mutants remained highly virulent to corn under some host physiological conditions. Here, we used the cga1 strain as a model for developing an in vivo sensitive and accurate pathogenicity assay. A detailed and well controlled analysis of wild type (WT) and cga1 pathogenic behavior revealed that detached leaves are significantly more vulnerable to the disease than intact ones. In intact leaves, cga1 mutants were less infective of maize under most conditions. This difference was maximized when the first seedling leaf was chosen for inoculation and when the infected leaves, with spores or mycelia fragments droplets, were incubated for a period of four days. This optimal condition set enabled us to classify the C. heterostrophus G-protein signaling mutants deficient in α, β or both subunits in order of decreasing virulence: WT > cga1> cgb1> cga1 cgb1. The method presented proved to be accurate and sensitive enough to identify even slight variations in virulence. Moreover, it could be modified for use in studies of other foliar phytoparasitic fungi.
基金Supported by The Jichi Medical University 21st Century Center of Excellence Program from Minister Education,Culture,Sports,Science and Technology in Japan
文摘AIM To investigate whether GNB3 C825 T single nucleotide polymorphism(SNP)contributes to systolic blood pressure(SBP)≥130 mmH g in a large-scale cross-sectional study among the Japanese population with diastolic blood pressure(DBP)<85 mmH g.METHODS We analyzed 11008 Japanese subjects,including 2797 cases(SBP≥130 and DBP<85 mmH g)who were not taking anti-hypertensive medication and 8211 controls(SBP<130 and DBP<85 mmH g),all of whom enrolled in the genome banking project of the 21 st Century COE(Center of Excellence)Program at Jichi Medical University.Subjects were divided into four groups according to gender(male and female)and age(≤49 years and≥50 years).GNB3 gene polymorphism was determined using the TaqM an probe method.We compared the frequencies of alleles and genotypes between cases and controls by chi-squared test.The strength of the associations was estimated by odds ratios(ORs)and 95%CI by using logistic regression analysis.The ORs were adjusted for age and body mass index.RESULTS Allele and genotype distributions significantly differed between cases and controls only in males aged≤49 years.Compared to the CC genotype,a significant OR was obtained in the TT genotype among males aged≤49 years.CONCLUSION This study indicates that the TT genotype of the GNB3 C825 T SNP may contribute to SBP elevation of greater than 130 mmH g compared to the CC genotype in Japanese males aged≤49 years.
基金supported by Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB01020300)the National Natural Science Foundation of China (Nos.21377158,21577149,21477139,21237005,21621064 and 21321004)
文摘Bisphenol A(BPA) is one of the highest volume industrial products worldwide and has been widely used to make various products as the intermediates of polycarbonate plastics and epoxy resins.Inevitably, general population has been widely exposed to BPA due to extensive use of BPAcontaining products. BPA has similar chemical structure with the natural estrogen and has been shown to induce a variety of estrogen-like endocrine effects on organism in vivo or in vitro. High doses of BPA tend to act as antagonist of estrogen receptors(ERs) by directly regulating the genomic transcription. However, BPA at environmentally relevant low-dose always disrupt the biological function via a non-genomic manner mediated by membrane receptors, rather than ERs. Although some studies had investigated the non-genomic effects of low-dose BPA, the exact molecular mechanism still remains unclear. Recently, we found that membrane G protein-coupled estrogen receptor 1 and integrin αvβ3 and its relative signal pathways participate in the induction of male germ cell proliferation and thyroid transcription disruption by the low-dose BPA. A profound understanding for the mechanism of action of the environmentally relevant BPA exposure not only contributes to objectively evaluate and predict the potential influence to human health, but also provides theoretical basis and methodological support for assessing health effects trigged by other estrogen-like environmental endocrine disruptors. Based mainly on our recent findings, this review outlines the research progress of molecular mechanism on endocrine disrupting effects of environmental low-dose BPA, existing problems and some consideration for future studies.
基金supported by the National Natural Science Foundation of China(32370281)the Young Talent fund of University Association for Science and Technology in Shaanxi,China(20210205)the Chinese Universities Scientific Fund(2452023069).
文摘Heterotrimeric G-proteins,comprising Gα,Gβ,and Gγsubunits,act as crucial molecular switches for signaling transduction in all eukaryotic organisms.Through precise modulation of specific receptors or effectors coupled with heterotrimeric G-proteins in signaling cascades,plants have the capability to activate or suppress unique signaling pathways necessary for plant growth,development,and stress responses.This review provides an overview of the heterotrimeric G-proteins signaling pathway obtained to date,and highlights novel areas for future exploration and agricultural application based on the emerging significance and potential of heterotrimeric G proteins in regulating plant development and responses to abiotic stress.
基金supported by the Major Demonstration Project of the Open Competition for Seed Industry Science and Technology Innovation in Inner Mongolia(2022JBGS0016)the National Natural Science Foundation of China(32370253)+1 种基金the National Key Research and Development Program of China(2023YFF1001400,and 2022YFA0912100)a Faculty Resources Project of the College of Life Sciences,Inner Mongolia University(2022-101).
文摘Heterotrimeric G proteins are crucial transducers of signaling from receptors,participating in growth and development,as well as in responses to biotic and abiotic stimuli.However,little is known about their roles in regulating various yield-related traits in legumes.In this study,we systematically analyzed the functions of two G-protein-encoding genes,MtGα1 and MtGβ1,along with Regulator of G-protein Signaling1(MtRGS1),in Medicago truncatula.All three genes were ubiquitously expressed in roots,stems,leaves,nodules,flowers,and pods.We generated the knockout mutants Mtgα1,Mtgβ1,and Mtrgs1 using CRISPR/Cas9 and assessed their growth and development.MtGα1 knockout resulted in slightly shorter plants with smaller pods and shorter spines,but larger seeds,without affecting overall biomass or other traits.MtGβ1 knockout led to dwarfism,weak root development,a severe drop in biomass production,smaller legume pods with shorter spines,and smaller seeds.However,the Mtrgs1 mutants were largely similar to wild-type plants,with few significant defects in growth and development.We also investigated the symbiotic nodulation-related phenotypes of these mutants,discovering that Mtgβ1 mutants produce lighter nodules,whereas Mtgα1 and Mtrgs1 mutants have normal nodulation phenotypes similar to those of wild-type plants.These observations suggest that MtGβ1 positively regulates nodulation,although the detailed mechanisms by which G proteins regulate symbiotic nitrogen fixation in M.truncatula remain to be explored.This work provides potentially valuable genetic resources for further functional analysis and elucidation of the molecular mechanisms of G proteins in this model legume.
文摘Heterotrimeric GTP-binding proteins, which consist of Gα, Gβ, and Gγ subunits, play important roles in transducing extracellular signals perceived by cell surface receptors into intracellular physiological responses. In addition to a single prototypical Gα protein （GPA1）, Arabidopsis has three unique Gα-Iike proteins, known as XLG1, XLG2, and XLG3, that have been found to be localized in nuclei, although their functions and mode of action remain largely unknown. Through a transcriptomic analysis, we found that XLG2 and XLG3 were rapidly induced by infection with the bacterial pathogen Pseudomonas syringae, whereas the XLG1 transcript level was not affected by pathogen infection. A reverse genetic screen revealed that the xlg2 loss-of-function mutation causes enhanced susceptibility to P. syringae. Transcriptome profiling revealed that the xlg2 mutation affects pathogen-triggered induction of a small set of defense-related genes. However, xlgl and xlg3 mutants showed no difference from wild-type plants in resistance to P. syringae, In addition, the xlg2 xlg3 double mutant and the xlgl xlg2 xlg3 triple mutant were not significantly different from the xlg2 single mutant in the disease resistance phenotype, suggesting that the roles of XLG1 and XLG3 in defense, if any, are less significant than for XLG2. Constitutive overexpression of XLG2 leads to the accumulation of abnormal transcripts from multiple defense-related genes. Through co-immunoprecipitation assays, XLG2 was found to interact with AGB1, the sole Gβ subunit in Arabidopsis, which has previously been found to be a positive regulator in resistance to necrotrophic fungal pathogens. However, no significant difference was found between three xlg single mutants, the xlg2 xlg3 double mutant, the xlgtriple mutant, and wild-type plants in resistance to the necrotrophic fungal pathogens Botrytis cinerea or Alternaria brassicicola. These results suggest that XLG2 and AGB1 are components of a G-protein complex different from the prototypical heterotrimeric G-protein and may have distinct functions in modulating defense responses.
基金This work was supported by The National Natural Science Foundation of China grants to H.-Q.Y. （31530085, 91217307, and 90917014） and to H.L. Lian （31570282 and 31170266）, and the National Key Research and Devel- opment Program of China grant （2017YFA0503800）.
文摘Light and the heterotrimeric G-protein are known to antagonistically regulate photomorphogenesis in Arabidopsis. However, whether light and G-protein coordinate the regulation of photomorphogenesis is largely unknown. Here we show that the blue light photoreceptor cryptochrome 1 （CRY1） physically inter-acts with the G-protein β subunit, AGB1, in a blue light-dependent manner. We also show that AGB1 directly interacts with HY5, a basic leucine zipper transcriptional factor that acts as a critical positive regulator of photomorphogenesis, to inhibit its DNA-binding activity. Genetic studies suggest that CRY1 acts partially through AGB1, and AGB1 acts partially through HY5 to regulate photomorphogenesis. Moreover, we demonstrate that blue light-triggered interaction of CRY1 with AGB1 promotes the dissociation of HY5 from AGB1. Our results suggest that the CRY1 signaling mechanism involves positive regulation of the DNA-binding activity of HY5 mediated by the CRY1-AGB1 interaction, which inhibits the association of AGB1 with HY5. We propose that the antagonistic regulation of HY5 DNA-binding activity by CRY1 and AGB1 may allow plants to balance light and G-protein signaling and optimize photomorphogenesis.
文摘Hypocotyl development in Arabidopsis thaliana is regulated by light and endogenous hormonal cues, mak- ing it an ideal model to study the interplay between light and endogenous growth regulators. BBX21, a B-box （BBX）-Iike zinc-finger transcription factor, integrates light and abscisic acid signals to regulate hypocotyl elongation in Arabidopsis. Heterotrimeric G-proteins are pivotal regulators of plant development. The short hypocotyl phenotype of the G-protein I^-subunit （AGB1） mutant （agbl-2） has been previously identified, but the precise role of AGB1 in hypocotyl elongation remains enigmatic. Here, we show that AGB1 directly interacts with BBX21, and the short hypocotyl phenotype of agbl-2 is partially suppressed in agb1-2bbx21-1 double mutant. BBX21 functions in the downstream of AGB1 and overexpression of BBX21 in agbl-2 causes a more pronounced reduction in hypocotyl length, indicating that AGB1 plays an oppositional role in relation to BBX21 during hypocotyl development. Furthermore, we demonstrate that the C-terminal region of BBX21 is important for both its intracellular localization and its transcriptional activation activity that is inhibited by interaction with AGB1. ChiP assays showed that BBX21 specifically associates with its own promoter and with those of BBX22, HY5, and GA2oxl. which is not altered in agbl-2. These data suggest that the AGB1-BBX21 interaction only affects the transcrip- tional activation activity of BBX21 but has no effect on its DNA binding ability. Taken together, our data demonstrate that AGB1 positively promotes hypocotyl elongation through repressing BBX21 activity.
文摘The Arabidopsis heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi. The agbl mutant impaired in the Gβ subunit displays enhanced susceptibility to these pathogens. Gβ/AGB1 forms an obligate dimer with either one of the Arabidopsis Gγsubunits （γ1/AGG1 and γ2/AGG2）. Accordingly, we now demonstrate that the aggl agg2 double mutant is as susceptible as agbl plants to the necrotrophic fungus Plectosphaerella cucumerina. To elucidate the molecular basis of heterotrimeric G-protein-mediated resistance, we performed a comparative transcriptomic analysis of agbl-1 mutant and wild-type plants upon inoculation with P cucumerina. This analysis, together with metab- olomic studies, demonstrated that G-protein-mediated resistance was independent of defensive pathways required for resistance to necrotrophic fungi, such as the salicylic acid, jasmonic acid, ethylene, abscisic acid, and tryptophan-derived metabolites signaling, as these pathways were not impaired in agbl and aggl agg2 mutants. Notably, many mis-reguiated genes in agbl plants were related with cell wall functions, which was also the case in aggl agg2 mutant. Biochemical analyses and Fourier Transform InfraRed （FTIR） spectroscopy of cell walls from G-protein mutants revealed that the xylose content was lower in agbl and aggl agg2 mutants than in wild-type plants, and that mutant walls had similar FTIR spec-tratypes, which differed from that of wild-type plants. The data presented here suggest a canonical functionality of the Gβ and Gγ1/γ2 subunits in the control of Arabidopsis immune responses and the regulation of cell wall composition.
基金grants from the National Natural Science Foundation of China，Hunan Provincial Natural Science Foundation of China
文摘Background： G-protein β-polypeptide 3 （GNB3） is a β subunit isoform of G-protein that plays important role in signal transduction of membrane G-protein coupled receptors （GPCRs）. The GNB3 splice variant C825T （rs5443） is associated with risk for essential hypertension （EH） and efficacy of therapeutic drugs targeting GPCRs. It is unknown whether the polymorphism is associated with blood pressure （BP） response to telmisartan or amlodipine, two widely prescribed antihypertensive drugs. Methods： A total of 93 subjects initially diagnosed as EH were recruited and underwent a 4-week treatment with telmisartan （42 patients） or amlodipine （51 patients） monotherapy. Both baseline and after-treatment BP were measured. GNB3 C825T polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism. Results： Baseline systolic BP （SBP） and diastolic BP （DBP） were comparable among C825T genotypes in both telmisartan and amlodipine treatment groups. Patients with the CT or TT genotypes showed significantly lower body mass index （BMI） as compared with CC homozygotes in both groups （P 〈 0.05, respectively）. GNB3 825TT homozygotes showed significantly higher alier-treatment DBP and mean arterial presstire （MAP） than those carrying at least one 825C allele （P 〈 0.01） in the telmisartan treatment group. No difference in after-treatment SBE DBP, and MAP levels among C825T genotypes was observed in the amlodipine treatment group. No significant difference in absolute changes in BP levels was observed among the genotypes in either treatment group. Conchlsion： The GNB3 C825T splice variant is associated with the DBP-lowering effect of telmisartan but not amlodipine in Chinese EH patients.
