Nephrin mRNA regulation by protein kinase C

Background. Mutations in the recently cloned NPHS1 gene result in congenita l nephrotic syndrome of the Finnish type (CNF), The protein product of NPHS 1, nephrin, is expressed uniquely in kidney glomerular podocytes, and is th e first true component of the interpodocyte slit membrane. The precise func tions of nephrin remain unknown, but the presence of several tyrosine resid ues in the intracellular domain suggest a role in signalling, We searched f or nephrin expressing cell line for use in signal transduction studies and also characterized the main features of calcium signalling in nephrin-defic ient cultural glomerular epithelial cells. Methods. We used A293 cell line, found to naturally express nephrin, as wel l as cultured CNF glomerular cells using re verse-transcription PCR, immuno cytochemistry and intracellular Ca2+ measurements. Results. Phorbol-12-myristate-13-acetate significantly upregulated the neph rin expression in A293 cells, while no change was found after treatment wit h additional stimulants for other main signalling pathways, e,g, okadaic ac id, lysophosphatidic acid, bradykinin, angiotensin II (ANG II) and arginine vasopressin (AVP), No changes in basal or ANG II- or AVP-stimulated intrac ellular Ca2+ fluxes in CNF glomerular cells were observed. Conclusions. Protein kinase C may be the key intracellular signalling syste m in the regulation of nephrin.