Referenced in: none

Automatically associated channels: TRP , TRPC , TRPC6

Title: The proteoglycan syndecan 4 regulates transient receptor potential canonical 6 channels via RhoA/Rho-associated protein kinase signaling.

Authors: Ying Liu, Frank Echtermeyer, Florian Thilo, Gregor Theilmeier, Antje Schmidt, Ralf Schülein, Boye L Jensen, Christoph Loddenkemper, Vera Jankowski, Niels Marcussen, Maik Gollasch, William J Arendshorst, Martin Tepel

Journal, date & volume: Arterioscler. Thromb. Vasc. Biol., 2012 Feb , 32, 378-85

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/22155451

Abstract
Syndecan 4 (Sdc4) modulates signal transduction and regulates activity of protein channels. Sdc4 is essential for the regulation of cellular permeability. We hypothesized that Sdc4 may regulate transient receptor potential canonical 6 (TRPC6) channels, a determinant of glomerular permeability, in a RhoA/Rho-associated protein kinase-dependent manner.Sdc4 knockout (Sdc4(-/-)) mice showed increased glomerular filtration rate and ameliorated albuminuria under baseline conditions and after bovine serum albumin overload (each P<0.05). Using reverse transcription-polymerase chain reaction and immunoblotting, Sdc4(-/-) mice showed reduced TRPC6 mRNA by 79% and TRPC6 protein by 82% (each P<0.05). Sdc4(-/-) mice showed an increased RhoA activity by 87% and increased phosphorylation of ezrin in glomeruli by 48% (each P<0.05). Sdc4 knockdown in cultured podocytes reduced TRPC6 gene expression and reduced the association of TRPC6 with plasma membrane and TRPC6-mediated calcium influx and currents. Sdc4 knockdown inactivated negative regulatory protein Rho GTPase activating protein by 33%, accompanied by a 41% increase in RhoA activity and increased phosphorylation of ezrin (P<0.05). Conversely, overexpression of Sdc4 reduced RhoA activity and increased TRPC6 protein and TRPC6-mediated calcium influx and currents.Our results establish a previously unknown function of Sdc4 for regulation of TRPC6 channels and support the role of Sdc4 for the regulation of glomerular permeability.