Phosphodiesterase 5 inhibition ameliorates angiontensin II-induced podocyte dysmotility via the protein kinase G-mediated downregulation of TRPC6 activity

Abstract

The emerging role of the transient receptor potential cation channel isotype 6 (TRPC6) as a central contributor to various pathological processes affecting podocytes has generated interest in the development of therapeutics to modulate its function. Recent insights into the regulation of TRPC6 have revealed PKG as a potent negative modulator of TRPC6 conductance and associated signaling via its phosphorylation at two highly conserved amino acid residues: Thr69/Thr70 (Thr69 in mice and Thr70 in humans) and Ser321/Ser322 (Ser321 in mice and Ser322 in humans). Here, we tested the role of PKG in modulating TRPC6-dependent responses in primary and conditionally immortalized mouse podocytes. TRPC6 was phosphorylated at Thr69 in nonstimulated podocytes, but this declined upon ANG II stimulation or overexpression of constitutively active calcineurin phosphatase. ANG II induced podocyte motility in an in vitro wound assay, and this was reduced 30–60% in cells overexpressing a phosphomimetic mutant TRPC6 (TRPC6T70E/S322E) or activated PKG ( P < 0.05). Pretreatment of podocytes with the PKG agonists S-nitroso- N-acetyl-dl-penicillamine (nitric oxide donor), 8-bromo-cGMP, Bay 41–2772 (soluble guanylate cyclase activator), or phosphodiesterase 5 (PDE5) inhibitor 4-{[3′,4′-(methylenedioxy)benzyl]amino}[7]-6-methoxyquinazoline attenuated ANG II-induced Thr69 dephosphorylation and also inhibited TRPC6-dependent podocyte motility by 30–60%. These data reveal that PKG activation strategies, including PDE5 inhibition, ameliorate ANG II-induced podocyte dysmotility by targeting TRPC6 in podocytes, highlighting the potential therapeutic utility of these approaches to treat hyperactive TRPC6-dependent glomerular disease.