Objective:Hepatitis B virus(HBV)infection is a major public health problem worldwide.However,the regulatory mechanisms underlying HBV replication remain unclear.Cullin 4 B-RING ubiquitin E3 ligase(CRL4 B)is involved i...Objective:Hepatitis B virus(HBV)infection is a major public health problem worldwide.However,the regulatory mechanisms underlying HBV replication remain unclear.Cullin 4 B-RING ubiquitin E3 ligase(CRL4 B)is involved in regulating diverse physiological and pathophysiological processes.In our study,we aimed to explain the role of CUL4 B in HBV infection.Methods:Cul4 b transgenic mice or conditional knockout mice,as well as liver cell lines with CUL4 B overexpression or knockdown,were used to assess the role of CUL4 B in HBV replication.Immunoprecipitation assays and immunofluorescence staining were performed to study the interaction between CUL4 B and HBx.Cycloheximide chase assays and in vivo ubiquitination assays were performed to evaluate the half-life and the ubiquitination status of HBx.Results:The hydrodynamics-based hepatitis B model in Cul4 b transgenic or conditional knockout mice indicated that CUL4 B promoted HBV replication(P<0.05).Moreover,the overexpression or knockdown system in human liver cell lines validated that CUL4 B increased HBV replication in an HBx-dependent manner.Importantly,immunoprecipitation assays and immunofluorescence staining showed an interaction between CUL4 B and HBx.Furthermore,CUL4 B upregulated HBx protein levels by inhibiting HBx ubiquitination and proteasomal degradation(P<0.05).Finally,a positive correlation between CUL4 B expression and HBV pg RNA level was observed in liver tissues from HBV-positive patients and HBV transgenic mice.Conclusions:CUL4 B enhances HBV replication by interacting with HBx and disrupting its ubiquitin-dependent proteasomal degradation.CUL4 B may therefore be a potential target for anti-HBV therapy.展开更多
Dysregulated lineage commitment of mesenchymal stem cells(MSCs)contributes to impaired bone formation and an imbalance between adipogenesis and osteogenesis during skeletal aging and osteoporosis.The intrinsic cellula...Dysregulated lineage commitment of mesenchymal stem cells(MSCs)contributes to impaired bone formation and an imbalance between adipogenesis and osteogenesis during skeletal aging and osteoporosis.The intrinsic cellular mechanism that regulates MSC commitment remains unclear.Here,we identified Cullin 4B(CUL4B)as a critical regulator of MSC commitment.CUL4B is expressed in bone marrow MSCs(BMSCs)and downregulated with aging in mice and humans.Conditional knockout of Cul4b in MSCs resulted in impaired postnatal skeletal development with low bone mass and reduced bone formation.Moreover,depletion of CUL4B in MSCs aggravated bone loss and marrow adipose accumulation during natural aging or after ovariectomy.In addition,CUL4B deficiency in MSCs reduced bone strength.Mechanistically,CUL4B promoted osteogenesis and inhibited adipogenesis of MSCs by repressing KLF4 and C/EBPδexpression,respectively.The CUL4B complex directly bound to Klf4 and Cebpd and epigenetically repressed their transcription.Collectively,this study reveals CUL4B-mediated epigenetic regulation of the osteogenic or adipogenic commitment of MSCs,which has therapeutic implications in osteoporosis.展开更多
Toll-like receptors (TLRs) play critical roles in innate immunity and inflammation. The molecular mechanisms by which TLR signaling is fine-tuned remain to be completely elucidated. Cullin 4B (CUL4B), which assembles ...Toll-like receptors (TLRs) play critical roles in innate immunity and inflammation. The molecular mechanisms by which TLR signaling is fine-tuned remain to be completely elucidated. Cullin 4B (CUL4B), which assembles the CUL4B-RING E3 ligase complex (CRL4B), has been shown to regulate diverse developmental and physiological processes by catalyzing monoubiquitination for histone modification or polyubiquitination for proteasomal degradation. Here, we identified the role of CUL4B as an intrinsic negative regulator of the TLR-triggered inflammatory response. Deletion of CUL4B in macrophages increased the production of proinflammatory cytokines and decreased anti-inflammatory cytokine IL-10 production in response to pathogens that activate TLR3, TLR4, or TLR2. Myeloid cell-specific Cul4b knockout mice were more susceptible to septic shock when challenged with lipopolysaccharide, polyinosinic-polycytidylic acid or Salmonella typhimurium infection. We further demonstrated that enhanced TLR-induced inflammatory responses in the absence of CUL4B were mediated by increased GSK3β activity. Suppression of GSK3β activity efficiently blocked the TLR-triggered increase in proinflammatory cytokine production and attenuated TLR-triggered death in Cul4b mutant mice. Mechanistically, CUL4B was found to negatively regulate TLR-triggered signaling by epigenetically repressing the transcription of Pten, thus maintaining the anti-inflammatory PI3K-AKT-GSK3β pathway. The upregulation of PTEN caused by CUL4B deletion led to uncontrolled GSK3β activity and excessive inflammatory immune responses. Thus, our findings indicate that CUL4B functions to restrict TLR-triggered inflammatory responses through regulating the AKT-GSK3β pathway.展开更多
Objective:The E3 ligase,CRL4,plays diverse roles in different cellular processes,such as DNA damage,transcriptional regulation,cell cycle progression,and cell apoptosis.Our previous study showed that CUL4A and CUL4B h...Objective:The E3 ligase,CRL4,plays diverse roles in different cellular processes,such as DNA damage,transcriptional regulation,cell cycle progression,and cell apoptosis.Our previous study showed that CUL4A and CUL4B had a strong association with tobacco smoking risk in lung squamous cell carcinoma(SCC)and small cell lung carcinoma(SCLC).This study aimed to define the potential mechanism underlying the roles of CUL4A and CUL4B in the development of SCC and SCLC.Methods:We determined the role of CUL4A and CUL4B in the cell cycle and apoptosis of SCC and SCLC,and identified the key apoptosis-related gene involved in the oncogenic activity of CUL4B by Western blot,immunohistochemical staining,flow cytometry,and enzyme inhibition experiments.Results:We found that depletion of CUL4A and CUL4B reduced the proliferation of SCC and SCLC cells.cUL4Aknockdown but not CUL4Bknockdown arrested cells in Gl phase while upregulating P21 and cU L4Bknockdown promoted cell apoptosis through upregulation o f FOXO3A.Accordingly,CUL4B decreased FO X03A expression by activating the ERK signaling pathway and mediating FOXO3A degradation via the ubiquitin-proteasome pathway.Conclusions:These results identified the function of E3 ligase CRL4 in regulating SCC and SCLC cell proliferation,which provides a potential strategy for cancer therapy by targeting FOXO3A and the E3 ligase,CRL4.展开更多
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.81970508,81672425,818300178,8197148,81670520,and 31671427)the National Key Research and Development Program(Grant No.2018YFE0126500)+1 种基金the Key Research&Development Plan of Shandong Province(Grant No.2018YFJH0503)support from the Collaborative Innovation Center of Technology and Equipment for Biological Diagnosis and Therapy in Universities of Shandong。
文摘Objective:Hepatitis B virus(HBV)infection is a major public health problem worldwide.However,the regulatory mechanisms underlying HBV replication remain unclear.Cullin 4 B-RING ubiquitin E3 ligase(CRL4 B)is involved in regulating diverse physiological and pathophysiological processes.In our study,we aimed to explain the role of CUL4 B in HBV infection.Methods:Cul4 b transgenic mice or conditional knockout mice,as well as liver cell lines with CUL4 B overexpression or knockdown,were used to assess the role of CUL4 B in HBV replication.Immunoprecipitation assays and immunofluorescence staining were performed to study the interaction between CUL4 B and HBx.Cycloheximide chase assays and in vivo ubiquitination assays were performed to evaluate the half-life and the ubiquitination status of HBx.Results:The hydrodynamics-based hepatitis B model in Cul4 b transgenic or conditional knockout mice indicated that CUL4 B promoted HBV replication(P<0.05).Moreover,the overexpression or knockdown system in human liver cell lines validated that CUL4 B increased HBV replication in an HBx-dependent manner.Importantly,immunoprecipitation assays and immunofluorescence staining showed an interaction between CUL4 B and HBx.Furthermore,CUL4 B upregulated HBx protein levels by inhibiting HBx ubiquitination and proteasomal degradation(P<0.05).Finally,a positive correlation between CUL4 B expression and HBV pg RNA level was observed in liver tissues from HBV-positive patients and HBV transgenic mice.Conclusions:CUL4 B enhances HBV replication by interacting with HBx and disrupting its ubiquitin-dependent proteasomal degradation.CUL4 B may therefore be a potential target for anti-HBV therapy.
基金supported by grants from the National Key R&D Program of China(2022YFC2703700,2022YFC2703701 to Y.G.and 2022YFC2703700,2022YFC2703703 to G.S.)National Natural Science Foundation of China(31872810,82171851 to Y.G.+3 种基金31970559 to B.J.31970781 to G.S.)Key Research and Development Program of Shandong Province(2016GSF201143 to B.J.)Young Scholars Program of Shandong University(to B.J.)。
文摘Dysregulated lineage commitment of mesenchymal stem cells(MSCs)contributes to impaired bone formation and an imbalance between adipogenesis and osteogenesis during skeletal aging and osteoporosis.The intrinsic cellular mechanism that regulates MSC commitment remains unclear.Here,we identified Cullin 4B(CUL4B)as a critical regulator of MSC commitment.CUL4B is expressed in bone marrow MSCs(BMSCs)and downregulated with aging in mice and humans.Conditional knockout of Cul4b in MSCs resulted in impaired postnatal skeletal development with low bone mass and reduced bone formation.Moreover,depletion of CUL4B in MSCs aggravated bone loss and marrow adipose accumulation during natural aging or after ovariectomy.In addition,CUL4B deficiency in MSCs reduced bone strength.Mechanistically,CUL4B promoted osteogenesis and inhibited adipogenesis of MSCs by repressing KLF4 and C/EBPδexpression,respectively.The CUL4B complex directly bound to Klf4 and Cebpd and epigenetically repressed their transcription.Collectively,this study reveals CUL4B-mediated epigenetic regulation of the osteogenic or adipogenic commitment of MSCs,which has therapeutic implications in osteoporosis.
基金We thank Prof.Chengjiang Gao and Prof.Wei Zhao for their critically reading of the paper.This work was supported by the National Natural Science Foundation of China(81571523 and 31872810)the Natural Science Foundation of Shandong Province(ZR2016HZ01)the Key Research and Development Program of Shandong Province(2016ZDJS07A08 and 2017GSF218027).
文摘Toll-like receptors (TLRs) play critical roles in innate immunity and inflammation. The molecular mechanisms by which TLR signaling is fine-tuned remain to be completely elucidated. Cullin 4B (CUL4B), which assembles the CUL4B-RING E3 ligase complex (CRL4B), has been shown to regulate diverse developmental and physiological processes by catalyzing monoubiquitination for histone modification or polyubiquitination for proteasomal degradation. Here, we identified the role of CUL4B as an intrinsic negative regulator of the TLR-triggered inflammatory response. Deletion of CUL4B in macrophages increased the production of proinflammatory cytokines and decreased anti-inflammatory cytokine IL-10 production in response to pathogens that activate TLR3, TLR4, or TLR2. Myeloid cell-specific Cul4b knockout mice were more susceptible to septic shock when challenged with lipopolysaccharide, polyinosinic-polycytidylic acid or Salmonella typhimurium infection. We further demonstrated that enhanced TLR-induced inflammatory responses in the absence of CUL4B were mediated by increased GSK3β activity. Suppression of GSK3β activity efficiently blocked the TLR-triggered increase in proinflammatory cytokine production and attenuated TLR-triggered death in Cul4b mutant mice. Mechanistically, CUL4B was found to negatively regulate TLR-triggered signaling by epigenetically repressing the transcription of Pten, thus maintaining the anti-inflammatory PI3K-AKT-GSK3β pathway. The upregulation of PTEN caused by CUL4B deletion led to uncontrolled GSK3β activity and excessive inflammatory immune responses. Thus, our findings indicate that CUL4B functions to restrict TLR-triggered inflammatory responses through regulating the AKT-GSK3β pathway.
基金The National Natural Science Foundation of China(Grant No.81772620 and 31471341)the Key Science and Technology Project of Tianjin Chronic Disease Prevention and Control(Grant No.17XXMFSY00130)the National Science and Technology Major Project(Grant No.2018ZX09201-015).
文摘Objective:The E3 ligase,CRL4,plays diverse roles in different cellular processes,such as DNA damage,transcriptional regulation,cell cycle progression,and cell apoptosis.Our previous study showed that CUL4A and CUL4B had a strong association with tobacco smoking risk in lung squamous cell carcinoma(SCC)and small cell lung carcinoma(SCLC).This study aimed to define the potential mechanism underlying the roles of CUL4A and CUL4B in the development of SCC and SCLC.Methods:We determined the role of CUL4A and CUL4B in the cell cycle and apoptosis of SCC and SCLC,and identified the key apoptosis-related gene involved in the oncogenic activity of CUL4B by Western blot,immunohistochemical staining,flow cytometry,and enzyme inhibition experiments.Results:We found that depletion of CUL4A and CUL4B reduced the proliferation of SCC and SCLC cells.cUL4Aknockdown but not CUL4Bknockdown arrested cells in Gl phase while upregulating P21 and cU L4Bknockdown promoted cell apoptosis through upregulation o f FOXO3A.Accordingly,CUL4B decreased FO X03A expression by activating the ERK signaling pathway and mediating FOXO3A degradation via the ubiquitin-proteasome pathway.Conclusions:These results identified the function of E3 ligase CRL4 in regulating SCC and SCLC cell proliferation,which provides a potential strategy for cancer therapy by targeting FOXO3A and the E3 ligase,CRL4.
