title: Novel role of Vav1-Rac1 pathway in actin cytoskeleton regulation in interleukin-13-induced minimal change-like nephropathy.
abstract: Our established interleukin-13 (IL-13) overexpression rat model of minimal change-like nephropathy provided a platform to study the molecular signalling pathways in T-helper 2 (Th2) cytokine associated minimal change nephrotic syndrome (MCNS). We hypothesized that IL-13 may act directly on podocytes, causing podocyte foot process effacement and hence proteinuria in our rat model of minimal change-like nephropathy. The present study aimed firstly to delineate the glomerular 'gene signature' associated with IL-13-mediated dysregulation of podocyte-related proteins, and subsequently to investigate the role of the differentially regulated genes (DEGs) in IL-13-mediated podocyte injury. Glomerular transcriptional profile ofIL-13-overexpressed rats showed characteristic features of podocyte injury with 87% of podocyte-related genes being significantly down-regulated. Gene expression ofVav1was shown to be highly up-regulated in the glomeruli ofIL-13-overexpressed rats and pathway analysis of the DEGs suggested a possible novel role of Vav1 in podocyte cytoskeleton remodelling. Immunofluorescence examination demonstrated glomerular expression of Vav1 in rats which co-localized with synaptopodin, confirming podocyte expression. However, positive staining for the phosphorylated form of Vav1 (p-Vav1) was only seen inIL-13-overexpressed rats. Moreover,in vitroIL-13 stimulation of human podocytes resulted in phosphorylation of Vav1. This was associated with Rac1 activation and actin cytoskeleton rearrangement, which was abrogated inVav1knockdown podocytes. In conclusion, we have demonstrated the role of Vav1-Rac1 pathway characterized by phosphorylation of Vav1, activation of Rac1 and the subsequent actin cytoskeleton rearrangement in IL-13-induced podocyte injury, possibly explaining the podocyte foot process effacement seen in ourIL-13overexpression rat model.
authors.affiliation: Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore.|KTP-National University Children's Medical Institute, National University Hospital, Singapore 119260, Singapore.
authors.forename: Chang-Yien
authors.initials: CY
authors.lastname: Chan
authors.affiliation: Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore.|KTP-National University Children's Medical Institute, National University Hospital, Singapore 119260, Singapore.
authors.forename: Kar-Hui
authors.initials: KH
authors.lastname: Ng
authors.affiliation: Bioinformatics, Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore 138648, Singapore.
authors.forename: Jinmiao
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Microbiology, National University of Singapore, Singapore 117599, Singapore.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Biochemistry, National University of Singapore, Singapore 117599, Singapore.
authors.forename: Caroline Guat-Lay
authors.initials: CG
authors.lastname: Lee
authors.affiliation: Department of Pathology, Singapore General Hospital, Singapore 169608, Singapore.
authors.forename: Puay-Hoon
authors.initials: PH
authors.lastname: Tan
authors.affiliation: Cedars-Sinai Medical Center, Los Angeles, CA 90048, U.S.A.
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Jordan
authors.affiliation: Cancer Science Institute, National University of Singapore, Singapore 119260, Singapore.
authors.forename: Henry Yang
authors.initials: HY
authors.lastname: He
authors.affiliation: Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore paeyaphk@nus.edu.sg.|KTP-National University Children's Medical Institute, National University Hospital, Singapore 119260, Singapore.
authors.forename: Hui-Kim
authors.initials: HK
authors.lastname: Yap
keywords: cytokines; cytoskeleton; glomerulopathy; minimal change; podocytes; transcription profiling