Raci Contributes to Actin Organization in Glomerular Podocytes

摘要

Background/Aims: The function of glomerular podocytes is closely associated with the actin cytoskeleton. In this study, we studied the role of the small Rho-GTPase, Rad, in actin organization in podocytes. Methods: Conditionally immortalized mouse podocytes (MP) stably expressing nephrin or control plasmid were used. Results: In MP, Rad activity increased significantly at 1 week of differentiation. MP stably expressing nephrin showed Rad activity significantly higher and more sustained than vector-expressing control cells. Antibody-mediated cross-linking of nephrin also activated Rad. Differentiated MP showed more distinct lamellipodia/ cellular processes, as compared with undifferentiated cells, which was further augmented by nephrin expression. Transient transfection of constitutively active Rad markedly increased the number of lamellipodia/cellular processes in undifferentiated MP, while the Rad inhibitor caused actin cytoskeleton derangement in differentiating MP. In the rat model of puromycin aminonucleoside nephrosis, RhoA activity was increased at Day 7 (at the peak of proteinuria), while Rad activity increased significantly only at Day 14, when the recovery process had started. Conclusion: Rad is activated in differentiating MP and nephrin potentiates Radactivation. Rad likely contributes to lamellipodia formation in differentiating MP and may contribute to process formation in podocytes recovering from injuries.