Regulation of myocardial GPCRs by USP20 in normal and hypertrophied heart

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PROJECT SUMMARY Chronic pressure overload that leads to left ventricular hypertrophy (LVH) and adverse cardiac remodeling is one of the leading causes of heart failure and affects millions of Americans. In addition to pathological insults and biomechanical factors, neurohormonal pathways that involve coordinated signaling through β1 and β2 adrenergic receptors (ARs) can play a major role in myocardial adaptation to pressure overload. The factors that shift the myocardial response to pressure overload from adaptive to maladaptive LVH remain largely obscure. Our research has focused on the regulation of βAR trafficking and signaling by ubiquitination/deubiquitination mechanisms. We recently discovered that differential regulation of β1AR and β2AR endocytic trafficking can be achieved by the deubiquitinase (DUB) called ubiquitin-specific protease-20 (USP20), which we found deubiquitinates both βARs. In response to the βAR agonist (-)isoproterenol (Iso), USP20 is phosphorylated on Ser333 by protein kinase A (PKA); this phosphorylation inhibits USP20 DUB activity toward the β2AR and regulates trafficking of the β2AR to autophagosomes. USP20 phosphorylation occurs in vivo, as well: (1) USP20 phosphorylation is significantly elevated in failing human hearts when compared with non-failing hearts and (2) pressure overload achieved by transverse aortic constriction (TAC) triggers USP20 phosphorylation in cardiomyocytes of WT, but not β1AR KO mice. Accordingly, during LVH, USP20 phosphorylation requires β1AR activation in the heart and may play a role in pathologic remodeling in LVH and/or heart failure. We hypothesize that “USP20 and its phosphorylation status fine-tune βAR signal transduction, endocytic trafficking and autophagy, thus impacting cardiac remodeling in LVH.” We will test our hypotheses by addressing the following specific aims: (1) To determine the role of cardiomyocyte-USP20 in the development of cardiac dysfunction, (2) To determine the regulation of myocardial βAR signaling by USP20 Ser333 phosphorylation and (3) To determine the coordinated roles of β1AR and USP20 in regulating ubiquitination status of the autophagy protein Beclin1 and its effect in cardiomyocyte autophagy.