Small Molecule Disruption of Gβγ Signaling Inhibits the Progression of Heart Failure

Abstract

Rationale: Excess signaling through cardiac G␤␥ subunits is an important component of heart failure (HF) pathophysiology. They recruit elevated levels of cytosolic G protein-coupled receptor kinase (GRK)2 to agonist-stimulated ␤-adrenergic receptors (␤-ARs) in HF, leading to chronic ␤-AR desensitization and downregulation; these events are all hallmarks of HF. Previous data suggested that inhibiting G␤␥ signaling and its interaction with GRK2 could be of therapeutic value in HF. Objective: We sought to investigate small molecule G␤␥ inhibition in HF. Methods and Results: We recently described novel small molecule G␤␥ inhibitors that selectively block G␤␥-binding interactions, including M119 and its highly related analog, gallein. These compounds blocked interaction of G␤␥ and GRK2 in vitro and in HL60 cells. Here, we show they reduced ␤-AR-mediated membrane recruitment of GRK2 in isolated adult mouse cardiomyocytes. Furthermore, M119 enhanced both adenylyl cyclase activity and cardiomyocyte contractility in response to ␤-AR agonist. To evaluate their cardiac-specific effects in vivo, we initially used an acute pharmacological HF model (30 mg/kg per day isoproterenol, 7 days). Concurrent daily injections prevented HF and partially normalized cardiac morphology and GRK2 expression in this acute HF model. To investigate possible efficacy in halting progression of preexisting HF, calsequestrin cardiac transgenic mice (CSQ) with extant HF received daily injections for 28 days. The compound alone halted HF progression and partially normalized heart size, morphology, and cardiac expression of HF marker genes (GRK2, atrial natriuretic factor, and ␤-myosin heavy chain). Conclusions: These data suggest a promising therapeutic role for small molecule inhibition of pathological G␤␥ signaling in the treatment of HF. (Circ Res. 2010;107:532-539.)Key Words: G proteins Ⅲ adrenergic receptor Ⅲ G protein-coupled receptor kinases Ⅲ cardiomyopathy Ⅲ heart failure Ⅲ cardiomyocyte H eart failure (HF) is a devastating disease with poor prognosis, and remains a leading cause of death worldwide. 1,2 Excess signaling through cardiac G protein G␤␥ subunits is an important component of HF pathophysiology. In particular, they recruit elevated levels of cytosolic G protein-coupled receptor kinase 2 (GRK2) (␤-adrenergic receptor kinase [␤-ARK]1) to agonist-stimulated ␤-ARs in HF, 3 leading to the chronic ␤-AR desensitization, downregulation and pathological signaling that are hallmarks of HF. 4,5 Increasing evidence suggests a critical role for G␤␥-mediated signaling in HF. In particular, GRK2 is significantly upregulated in cardiomyocytes of animal models of HF and human HF patients; this elevates G␤␥-GRK2 interactions and contributes to chronic desensitization of ␤-AR signaling 6,7 ; interestingly, levels of GRK2 appear to correlate with the severity of HF. 6,8 Enhancing G␤␥-GRK2 interaction by cardiac targeted overexpression of GRK2(s) can directly cause HF in experimental animal models 9 ; its genetic ablation has generally proven to be...

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