BCL2 is best known as a multifnnctional anti-apoptotic protein. However, little is known about its role in cell- adhesive and motility events. Here, we show that BCL2 may play a role in the regulation of cell adhesion...BCL2 is best known as a multifnnctional anti-apoptotic protein. However, little is known about its role in cell- adhesive and motility events. Here, we show that BCL2 may play a role in the regulation of cell adhesion, spreading, and motility. When BCL2 was overexpressed in cultured murine and human cell lines, cell spreading, adhesion, and motility were impaired. Consistent with these results, the loss of Bcl2 resulted in higher motility observed in Bcl2- null mouse embryonic fibroblast （MEF） cells compared to wild type. The mechanism of BCL2 regulation of cell adhesion and motility may involve formation of a complex containing BCL2, actin, and gelsolin, which appears to functionally decrease the severing activity of gelsolin. We have observed that the lysate from MCF-7 and NIH3T3 cells that overexpressed BCL2 enhanced actin polymerization in cell-free in vitro assays. Confocal immunofluorescent localization of BCL2 and F-actin during spreading consistently showed that increased expression of BCL2 resulted in increased F-actin polymerization. Thus, the formation of BCL2 and gelsolin complexes （which possibly contain other proteins） appears to play a critical role in the regulation of cell adhesion and migration. Given the established correlation of cell motility with cancer metastasis, this result may explain why the expression Of BCL2 in some tumor cell types reduces the potential for metastasis and is associated with improved patient prognosis.展开更多
Pollen tube growth is an essential step during flowering plant reproduction, whose growth depends on a population of dynamic apical actin filaments. Apical actin filaments were thought to be involved in the regu- lati...Pollen tube growth is an essential step during flowering plant reproduction, whose growth depends on a population of dynamic apical actin filaments. Apical actin filaments were thought to be involved in the regu- lation of vesicle fusion and targeting in the pollen tube. However, the molecular mechanisms that regulate the construction of apical actin structures in the pollen tube remain largely unclear. Here, we identify profilin as an important player in the regulation of actin polymerization at the apical membrane in the pollen tube. Downregulation of profilin decreased the amount of filamentous actin and induced disorganization of apical actin filaments, and reduced tip-directed vesicle transport and accumulation in the pollen tube. Direct visualization of actin dynamics revealed that the elongation of actin filaments originating at the apical membrane decreased in profilin mutant pollen tubes. Mutant profilin that is defective in binding poly-L-proline only partially rescues the actin polymerization defect in profilin mutant pollen tubes, although it fully rescues the actin turnover phenotype. We propose that profilin controls the construction of actin structures at the pollen tube tip, presumably by favoring formin-mediated actin polymerization at the apical membrane.展开更多
Protein phosphorylation is one of the most common post-translational modification processes that play an essential role in regulating protein functionality.The Helicoverpa armigera single nucleopolyhedrovirus (HearNPV...Protein phosphorylation is one of the most common post-translational modification processes that play an essential role in regulating protein functionality.The Helicoverpa armigera single nucleopolyhedrovirus (HearNPV) orf2-encoded nucleocapsid protein HA2 participates in orchestration of virus-induced actin polymerization through its WCA domain,in which phosphorylation status are supposed to be critical in respect to actin polymerization.In the present study,two putative phosphorylation sites (232Thr and 250Ser) and a highly conserved Serine (245Ser) on the WCA domain of HA2 were mutated,and their phenotypes were characterized by reintroducing the mutated HA2 into the HearNPV genome.Viral infectivity assays demonstrated that only the recombinant HearNPV bearing HA2 mutation at 245Ser can produce infectious virions,both 232Thr and 250Ser mutations were lethal to the virus.However,actin polymerization assay demonstrated that all the three viruses bearing HA2 mutations were still capable of initiating actin polymerization in the host nucleus,which indicated the putative phosphorylation sites on HA2 may contribute to HearNPV replication through another unidentified pathway.展开更多
Chemokine CXCL12 plays a crucial role in both direct bactericidal activity and phagocytosis in humans.However,the mechanisms and evolutionary functions of these processes in vertebrates remain largely unknown.In this ...Chemokine CXCL12 plays a crucial role in both direct bactericidal activity and phagocytosis in humans.However,the mechanisms and evolutionary functions of these processes in vertebrates remain largely unknown.In this study,we found that the direct bactericidal activity of CXCL12 is highly conserved across various vertebrate lineages,including Arctic lamprey(Lampetra japonica),Basking shark(Cetorhinus maximus),grass carp(Ctenopharyngodon idella),Western clawed frog(Xenopus tropicalis),Green anole(Anolis carolinensis),chicken(Gallus gallus),and human(Homo sapiens).CXCL12 also has been shown to promote phagocytosis in lower and higher vertebrates.We then employed C.idella CXCL12a(CiCXCL12a)as a model to further investigate its immune functions and underlying mechanisms.CiCXCL12a exerts direct broad-spectrum antibacterial activity by targeting bacterial acidic phospholipids,resulting in bacterial cell membrane perforation,and eventual lysis.Monocytes/macrophages are attracted to the infection sites for phagocytosis through the rapid production of CiCXCL12a during bacterial infection.CiCXCL12a induces CDC42 and CDC42 GTPase activation,which in turn mediates F-actin polymerization and cytoskeletal rearrangement.The interaction between F-actin and Aeromonas hydrophila facilitates bacterial internalization into monocytes/macrophages.Additionally,A.hydrophila is colocalized within early endosomes,late endosomes and lysosomes,ultimately degrading within phagolysosomes.CiCXCL12a also activates PI3K-AKT,JAK-STAT5 and MAPK-ERK signaling pathways.Notably,only the PI3K-AKT signaling pathway inhibits LPS-induced monocyte/macrophage apoptosis.Thus,CiCXCL12a plays key roles in reducing tissue bacterial loads,attenuating organ injury,and decreasing mortality rates.Altogether,our findings elucidate the conserved mechanisms underlying CXCL12-mediated bactericidal activity and phagocytosis,providing novel perspectives into the immune functions of CXCL12 in vertebrates.展开更多
文摘BCL2 is best known as a multifnnctional anti-apoptotic protein. However, little is known about its role in cell- adhesive and motility events. Here, we show that BCL2 may play a role in the regulation of cell adhesion, spreading, and motility. When BCL2 was overexpressed in cultured murine and human cell lines, cell spreading, adhesion, and motility were impaired. Consistent with these results, the loss of Bcl2 resulted in higher motility observed in Bcl2- null mouse embryonic fibroblast （MEF） cells compared to wild type. The mechanism of BCL2 regulation of cell adhesion and motility may involve formation of a complex containing BCL2, actin, and gelsolin, which appears to functionally decrease the severing activity of gelsolin. We have observed that the lysate from MCF-7 and NIH3T3 cells that overexpressed BCL2 enhanced actin polymerization in cell-free in vitro assays. Confocal immunofluorescent localization of BCL2 and F-actin during spreading consistently showed that increased expression of BCL2 resulted in increased F-actin polymerization. Thus, the formation of BCL2 and gelsolin complexes （which possibly contain other proteins） appears to play a critical role in the regulation of cell adhesion and migration. Given the established correlation of cell motility with cancer metastasis, this result may explain why the expression Of BCL2 in some tumor cell types reduces the potential for metastasis and is associated with improved patient prognosis.
文摘Pollen tube growth is an essential step during flowering plant reproduction, whose growth depends on a population of dynamic apical actin filaments. Apical actin filaments were thought to be involved in the regu- lation of vesicle fusion and targeting in the pollen tube. However, the molecular mechanisms that regulate the construction of apical actin structures in the pollen tube remain largely unclear. Here, we identify profilin as an important player in the regulation of actin polymerization at the apical membrane in the pollen tube. Downregulation of profilin decreased the amount of filamentous actin and induced disorganization of apical actin filaments, and reduced tip-directed vesicle transport and accumulation in the pollen tube. Direct visualization of actin dynamics revealed that the elongation of actin filaments originating at the apical membrane decreased in profilin mutant pollen tubes. Mutant profilin that is defective in binding poly-L-proline only partially rescues the actin polymerization defect in profilin mutant pollen tubes, although it fully rescues the actin turnover phenotype. We propose that profilin controls the construction of actin structures at the pollen tube tip, presumably by favoring formin-mediated actin polymerization at the apical membrane.
基金National Nature Science Foundations of China (31030027,30770085 and 30800044)
文摘Protein phosphorylation is one of the most common post-translational modification processes that play an essential role in regulating protein functionality.The Helicoverpa armigera single nucleopolyhedrovirus (HearNPV) orf2-encoded nucleocapsid protein HA2 participates in orchestration of virus-induced actin polymerization through its WCA domain,in which phosphorylation status are supposed to be critical in respect to actin polymerization.In the present study,two putative phosphorylation sites (232Thr and 250Ser) and a highly conserved Serine (245Ser) on the WCA domain of HA2 were mutated,and their phenotypes were characterized by reintroducing the mutated HA2 into the HearNPV genome.Viral infectivity assays demonstrated that only the recombinant HearNPV bearing HA2 mutation at 245Ser can produce infectious virions,both 232Thr and 250Ser mutations were lethal to the virus.However,actin polymerization assay demonstrated that all the three viruses bearing HA2 mutations were still capable of initiating actin polymerization in the host nucleus,which indicated the putative phosphorylation sites on HA2 may contribute to HearNPV replication through another unidentified pathway.
基金supported by the National Natural Science Foundation of China (32373164,31873044)。
文摘Chemokine CXCL12 plays a crucial role in both direct bactericidal activity and phagocytosis in humans.However,the mechanisms and evolutionary functions of these processes in vertebrates remain largely unknown.In this study,we found that the direct bactericidal activity of CXCL12 is highly conserved across various vertebrate lineages,including Arctic lamprey(Lampetra japonica),Basking shark(Cetorhinus maximus),grass carp(Ctenopharyngodon idella),Western clawed frog(Xenopus tropicalis),Green anole(Anolis carolinensis),chicken(Gallus gallus),and human(Homo sapiens).CXCL12 also has been shown to promote phagocytosis in lower and higher vertebrates.We then employed C.idella CXCL12a(CiCXCL12a)as a model to further investigate its immune functions and underlying mechanisms.CiCXCL12a exerts direct broad-spectrum antibacterial activity by targeting bacterial acidic phospholipids,resulting in bacterial cell membrane perforation,and eventual lysis.Monocytes/macrophages are attracted to the infection sites for phagocytosis through the rapid production of CiCXCL12a during bacterial infection.CiCXCL12a induces CDC42 and CDC42 GTPase activation,which in turn mediates F-actin polymerization and cytoskeletal rearrangement.The interaction between F-actin and Aeromonas hydrophila facilitates bacterial internalization into monocytes/macrophages.Additionally,A.hydrophila is colocalized within early endosomes,late endosomes and lysosomes,ultimately degrading within phagolysosomes.CiCXCL12a also activates PI3K-AKT,JAK-STAT5 and MAPK-ERK signaling pathways.Notably,only the PI3K-AKT signaling pathway inhibits LPS-induced monocyte/macrophage apoptosis.Thus,CiCXCL12a plays key roles in reducing tissue bacterial loads,attenuating organ injury,and decreasing mortality rates.Altogether,our findings elucidate the conserved mechanisms underlying CXCL12-mediated bactericidal activity and phagocytosis,providing novel perspectives into the immune functions of CXCL12 in vertebrates.
