Inhibition of TRPC6 Channel Activity Contributes to the Antihypertrophic Effects of Natriuretic Peptides-Guanylyl Cyclase-A Signaling in the Heart

Abstract

Rationale: Atrial and brain natriuretic peptides (ANP and BNP, respectively) exert antihypertrophic effects in the heart via their common receptor, guanylyl cyclase (GC)-A, which catalyzes the synthesis of cGMP, leading to activation of protein kinase (PK)G. Still, much of the network of molecular mediators via which ANP/BNP-GC-A signaling inhibit cardiac hypertrophy remains to be characterized. Objective: We investigated the effect of ANP-GC-A signaling on transient receptor potential subfamily C (TRPC)6, a receptor-operated Ca 2؉ channel known to positively regulate prohypertrophic calcineurin-nuclear factor of activated T cells (NFAT) signaling. Methods and Results: In cardiac myocytes, ANP induced phosphorylation of TRPC6 at threonine 69, the PKG phosphorylation site, and significantly inhibited agonist-evoked NFAT activation and Ca 2؉ influx, whereas in HEK293 cells, it dramatically inhibited agonist-evoked TRPC6 channel activity. These inhibitory effects of ANP were abolished in the presence of specific PKG inhibitors or by substituting an alanine for threonine 69 in TRPC6. In model mice lacking GC-A, the calcineurin-NFAT pathway is constitutively activated, and BTP2, a selective TRPC channel blocker, significantly attenuated the cardiac hypertrophy otherwise seen. Conversely, overexpression of TRPC6 in mice lacking GC-A exacerbated cardiac hypertrophy. BTP2 also significantly inhibited angiotensin II-induced cardiac hypertrophy in mice. Conclusions: Collectively, these findings suggest that TRPC6 is a critical target of antihypertrophic effects elicited via the cardiac ANP/BNP-GC-A pathway and suggest TRPC6 blockade could be an effective therapeutic strategy for preventing pathological cardiac remodeling. (Circ Res. 2010;106:1849-1860.)Key Words: natriuretic peptides Ⅲ calcium Ⅲ ion channels Ⅲ hypertrophy I n response to pathological stimuli such as prolonged mechanical stress, massive tissue injury, or abnormal neurohumoral activation, hearts show hypertrophic growth and remodeling, which is characterized by an increase in myocyte cell size, assembly of sarcomere proteins, interstitial fibrosis, and reexpression of fetal cardiac genes. Although the hypertrophic response is initially compensatory, it ultimately causes heart failure, which is now a leading cause of morbidity and mortality around the world. Diverse intracellular signaling pathways exerting pro-or antihypertrophic effects have been shown to play important roles in the complex processes of cardiac remodeling, 1,2 but the details of the molecular mechanisms mediating the crosstalk among these signaling pathways remain uncertain. Unraveling those details should give us a better understanding of the molecular processes underlying the establishment of cardiac hypertro- phy and heart failure, which could ultimately lead to the discovery of novel therapeutic targets for prevention of pathological cardiac remodeling. The heart regulates cardiovascular homeostasis in part by secreting 2 peptide mediators, atrial natriuretic peptide (ANP) and brain n...

Combined TRPC3 and TRPC6 blockade by selective small-molecule or genetic deletion inhibits pathological cardiac hypertrophy

“…TRPC6 contains two residues in the N terminus, T70 and S322, that when phosphorylated by protein kinase G (PKG) potently suppress channel conductance and corresponding NFAT activation (9,21). Thus, we tested whether the TRPC3/6 antagonists were redundant or additive to this potent posttranslational regulation.…”

Gain-of-function Mutations in Transient Receptor Potential C6 (TRPC6) Activate Extracellular Signal-regulated Kinases 1/2 (ERK1/2)

“…3C), further arguing against a role for CaMKII in mediating ERK activation by mutant TRPC6 and suggesting that the effect of KN-93 on this process is mediated, at least in part, independently of its effect on CaMKII activity. Previous studies have suggested that PKA and cGMP-dependent protein kinase (PKG) might play a role in limiting the activity of the TRPC6 channel (82)(83)(84)(85)(86)(87). We therefore examined whether inhibition of PKA through H89 might further enhance ERK phosphorylation in cells expressing TRPC6 R895C.…”

TRP Channels: Their Function and Potentiality as Drug Targets

“…Increased PKG activity attenuates Ca 2+ /calcineurin-dependent cardiomyocyte hypertrophy induced by receptor stimulation and mechanical stretch, and mutation of the PKG phosphorylation site on TRPC6 canceled this inhibitory effect [ 157 ]. In contrast, decreased cGMP/PKG signaling by deletion of the guanylate cyclase (GC)-A gene was associated with development of spontaneous cardiac hypertrophy through TRPC3/6 channel activation [ 158 ]. Actually, this hypertrophy was attenuated by treatment with Pyr2, an inhibitor of all TRPC channels.…”

“…For example, α1 adrenergic receptorstimulated hypertrophic responses were blocked by 2-aminoethoxydiphenylborane (2-APB) and N-{4-[3,5-bis(trifl uoromethyl)-1H-pyrazol-1yl]phenyl}-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP2; also called Pyr2), but not by verapamil, a voltage-dependent L-type Ca 2+ channel blocker [ 142 ]. Indirect inhibition of TRPC3/6 channel activities by PDE-5 inhibitors [ 159 ] and ANP [ 158 ] can also suppresses pathological hypertrophy through phosphorylation of TRPC6 at Thr69. Mori developed a pyrazole compound, Pyr3, which selectively inhibits TRPC3 channel activity with an IC 50 value of 0.7 μM [ 36 ].…”