Mechanism Of Sos2 Inhibits NFATc1 Mediated Podocyte Injury In Diabetic Nephropathy

BackgroundDiabetes is the most importent underlying cause of chronic kidney disease?CKD?^[1].Diabetic nephropathy?DN?is one of the leading causes of chronic and end-stage renal disease?ESRD?worldwide,and its pathogenesis is closely related to many factors^[2].Almost all glomerular diseases are associated with podocyte injury^[3].There are many research reports that^[4]:The decrease of the number of podocytes in diabetic nephropathy is closely related to the occurrence of proteinuria.Therefore,it is of great significance to research the role of podocyte in the development of diabetic nephropathy.Guanine nucleotide exchange factors Sos?Son of sevenless?is an activator of Ras and Rac^[5],it can promote guanine nucleotide exchange?GDP/GTP?.The two known members of the mammalian Sos family?Sos1 and Sos2?code for ubiquitously expressed.In the kidney research field,The Sos2 protein is expressed in the glomeruli and tubules of kidneys from adult humans^[6].Up to now,the research of Sos2 in podocyte has not been reported.In addition,CAN-NFAT signaling pathway plays a central role in the pathogenesis of glomerular disease.Therefore,we are dedicated to investigate whether Sos2 participating in CAN-NFAT signal pathway,affecting the structure and function of podocytes,then regulating the fundamental mechanisms of diabetic nephropathy.ObjectiveThis research first observed the expression of Sos2 in podocyte.The effects of Sos2 on the injury and activity of podocyte were detected.Finally,exploring the mechanisms and influence of Sos2 acting on diabetic nephropathy.Methods1.In this research,human renopuncture tissues was used as the model,The expression of Sos2 in diabetic nephropathy podocyte was observed by immunofluorescence staining and laser confocal microscopy.2.In vitro,the Sos2 expression at mRNA and protein levels in immortalized podocytes with HG?30mmol/L glucose?stimulation for 48h was determined by the methods of RT-PCR,Western blot and immunofluorescence.3.Using Western blot,immunofluorescence,would-healing assay and Transwell assays,the expression of podocin,the translocation of NFATc1 into the nucleus and the podocyte migration with or without Sos2silencing or overexpression were analyzed.4.The expression of downstream target genes for NFATc1 was detected by RT-PCR.5.The correlation between Sos2 and TRPC6 was observed by immunoprecipitation.Results1.The expression of Sos2 was significantly decreased in the podocytes of diabetic nephropathy patients and in vitro cultured podocytes with HG stimulation?p<0.05?.2.When Sos2 was silenced,the expression of podocin was significantly decreased,the migration ability of podocytes was increased,and the translocation of NFATc1 into the nucleus was increased?p<0.05?.3.In contrast,after overexpression of Sos2 in the podocytes with HG stimulation,the podocin expression level was obviously higher,and the podocyte migration ability and the translocation of NFATc1 into the nucleus was decreased?p<0.05?.4.The immunoprecipitation results showed that Sos2 binds to TRPC6 protein,and Sos2 inhibited the expression of TRPC6.ConclusionSos2 expressed in podocytes,and with HG stimulation,the expression of Sos2 was significantly decreased in the podocytes.Sos2 is a protective factor in diabetic nephropathy podocytes,probably by combining with TRPC6,participating in CAN-NFAT signal axis,thus inhibiting the translocation of NFATc1 into the nucleus and alleviating podocyte injury in diabetic nephropathy.