SM22,an Actin Binding Protein, Regulates PDGF-mediated GLUT4Translocation via Actin Filament Remodeling

【摘要】：SM22,an Actin Binding Protein,Regulates PDGF-mediated GLUT4 Translocation via ActinFilament RemodelingLiLi Zhao,Peng Chen,Xiao-Li Xie,Yong-Qing Dou,Mei HanDepartment of Biochemistry and Molecular Biology,Hebei Medical UniversityObjectives:Platelet derived growth factor(PDGF),is a potent mitogen which stimulates theproliferation and migration of cells.In addition,PDGF increase the rate of glucose transportwhich plays a fundamental role in cellular growth and proliferation.GLUT4,as an importantglucose transporter in vascular smooth muscle cells(VSMCs),translocates to theplasma membrane in an actin dynamics-dependent manner where they participate in glucoseuptake.SM22,an actin binding protein,participated in stress fiber formation and actindynamics.We hypothesized that SM22 may contribute to PDGF-regulated GLUT4 traffic.Methods and Results:Immunofluorescence and western blot showed that PDGF increasedGLUT4 translocation,via promoting cortical polymerization in VSMCs.Knockdown ofSM22 by siRNA ledto the thinning and dispersion of actin filaments,and enhanced PDGFinducedcortical actin polymerization,accompanied by increased GLUT4 translocation.Conversely,overexpression of SM22 reduced GLUT4 translocation,in parallel with inhibitionof cortical actin remodeling.This finding was verified in VSMCs of Sm22-/-mice.Using2-NBDG,a fluorescence probe,to detect the glucose uptake,we showed that loss ofSM22 promoted 2-NBDG uptake.Furthermore,we found an increased activity of lactic dehydrogenase(LDH),a key enzyme of glycolysis,in VSMCs with SM22 knockdown or fromSm22-/-mice upon PDGF stimulation.Conclusion:Our findings suggest that downregulation of SM22 facilitates GLUT4 translocationthrough promoting cortical actin polymerization.This study provides initial evidencelinking the cytoskeleton remodeling with glucose metabolism in VSMCs.