Insulin Increases Glomerular Barrier Permeability: Role of Intracellular Calcium and PKGIα‐Dependent Signaling

Abstract

Podocytes are dynamic polarized cells that lie on the surface of glomerular capillaries and comprise an essential component of the glomerular filtration barrier. We demonstrated recently that insulin increasesactivation of protein kinase G type Ia (PKGIa) subunits, leading to podocyte dysfunction. Here we investigated whether intracellular calciumis involved in insulin-dependent regulation of filtration barrier permeability in PKGIα-dependent manner. The RT-PCR showed the presence of mRNAs encoding SERCA isoforms 1-3, PMCA isoforms 1,3,4 and TRPC6 channel in podocyte. The thapsigargin (TG, SERCA inhibitor) and SKF96365 (TRPC inhibitor) abolished insulin-dependent glomerular albumin permeability in Wistar rats and PKGI-dependent transmembrane albumin flux in cultured podocytes. The same result we observed after preincubation cells with PKGI inhibitor Rp-8-cGMPS. Our data showed that insulin evoked a sustained increase of [Ca2+]in in podocytes, about 69%. This [Ca2+]in increase was blocked by TG and SKF96365. Furthermore, Rp-8-cGMPS strongly reduced the insulin-induced [Ca2+]in increase, about 71%. Moreover, the TG and SKF96365 abolished insulin induce changes in the phosphorylation of the PKG target proteins MYPT1 and RhoA. The results indicate that insulin increases filtration barrier permeability through increase level of intracellular Ca2+ concentration and via PKGIα activation in podocytes. This work was supported by grant from the FNP (POMOST/2011-4/6) and from the NSC (2012/05/B/NZ4/02587).