Pyk2 controls filamentous actin formation in human glomerular mesangial cells via modulation of profilin expression

Victoriya A Rufanova¹, Anna Alexanian¹, Tetsuro Wakatsuki^2,3, Andrey Sorokin¹

¹Department of Medicine, Division of Nephrology, Kidney Disease Center Milwaukee, WI, USA; ²Department of Physiology, ³Bioengineering and Biotechnology Center, Medical College of Wisconsin, Milwaukee, WI, USA

Abstract: In glomerular mesangial cell (GMC), important regulators of glomerular filtration, adenovirus-mediated overexpression of calcium regulated nonkinase (CRNK), a dominant interfering calcium-regulated nonreceptor proline-rich tyrosine kinase 2 (Pyk2) construct, inhibited Pyk2 activity and caused enhanced RhoA activity, enriched cortical actin formation at time of cell replating, and reduction of spreading. We aimed to further explore Pyk2 regulation of the actin dynamic during cell spreading as a vital characteristic of GMC function. GMC were infected with adenovirus encoding CRNK or green fluorescent protein (GFP) as a control and 48 hours after infection cells were harvested and either re-plated or left in suspension for one hour. De novo adhesion to substrate was significantly decreased after Pyk2 activity inhibition and was further diminished after treatment with Rho-associated kinase inhibitor. Inhibition of Pyk2 was associated with increased filamentous actin formation and a corresponding decrease in globular to filamentous actin ratio during cell spreading. Phosphorylation and expression of cofilin, a RhoA-regulated filamentous actin destabilizing factor, were similar in CRNK-expressing and control GMC. Expression of profilin, an activator of actin polymerization, was enhanced, whereas phosphorylation of Pyk2 and p130Cas was decreased. Our data suggest that Pyk2 signaling controls the filamentous actin formation during cell spreading via upregulation of profilin expression.

Keywords: Pyk2, profilin, cell spreading, adhesion, glomerular mesangial cells, p130Cas, actin dynamic, ROCK inhibition