Dysregulation of cardiac signaling in disease and stress

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Project Summary G-protein coupled receptor (GPCR) kinase-2 (GRK2) is a key regulator of GPCR recycling and desensitization that is upregulated in several cardiac pathologies, including hypertrophy and heart failure (HF). Cardiac ischemia-reperfusion injury induces ERK-mediated phosphorylation of GRK2 at S670, which results in the translocation of GRK2 from the cytosol to mitochondria. We discovered that in the adult cardiomyocyte mitochondrial GRK2 regulates glucose-mediated oxidative phosphorylation by inhibiting pyruvate dehydrogenase, the rate limiting enzyme of glucose oxidation. Although the physiological impact of mitochondrial GRK2 was reported, it remains largely unknown how mitochondrial GRK2 regulates cardiac mitochondrial metabolism. This proposal focuses on deciphering mechanistically how GRK2 phosphorylation and mitochondrial translocation regulate cardiac glucose metabolism. Additionally, we propose that mitochondrial GRK2 participates in key metabolic signaling post-myocardial infarction (MI) by acting as an amplifier of pyroptosis- a novel lytic cell death mechanism. Thus, we hypothesize that GRK2 phosphorylation at S670 is paramount for cardiomyocyte responses in consequence of altering metabolic availability and cardiac injury. Using a novel GRK-S670A and two Gasdermin E mouse models, we propose to carry out two specific aims: 1.) Determine how mitoGRK2 regulates cardiac mitochondrial metabolism; 2.) Assess whether phosphorylation of GRK2 at S670 modulates cardiac pyroptotic signaling. Overall, our work will shed light on the role of GRK2 phosphorylation at S670 in cardiomyocytes and how this post-translational modification regulates metabolic signaling and chronic-injury responses. The overarching goal of this research is to exploit novel mechanistic signaling for the development and identification of new pharmaceutical drugs for HF treatment.