Cardiomyocyte-specific Adhesion G Protein-Coupled Receptor F5 (ADGRF5) participates in cardiac homeostasis

Abstract

<b>Abstract ID 56061</b> <b>Poster Board 107</b> G protein-coupled receptors (GPCRs) remain the largest family of protein targets for approved drugs due to their impact on numerous physiologic and pathologic processes, as well as the relative ease of modulating their activity at cell surface-accessible sites. Although the heart expresses hundreds GPCRs, relatively few been explored as targets to reduce remodeling and preserve contractility during heart failure (HF). Adhesion GPCRs (AGPCRs) are an understudied family of receptors containing numerous extracellular domains that interact with various extracellular proteins, including many that are known mediators of cardiac remodeling responses to pathologic stress, thus may represent novel targets for HF. RNA-sequencing analysis of left ventricle (LV) tissue isolated from healthy hearts of adult mice identified high expression of several AGPCR family members, including ADGRF5, which was subsequently shown to become downregulated in transaortic constriction (TAC)-induced HF in mice. Further, analysis of published single cell-RNA-Seq datasets confirmed ADGRF5 expression specifically in cardiomyocytes becomes decreased over time in both mouse and human HF. Thus, to investigate the impact of cardiomyocyte-expressed ADGRF5 on cardiac function and remodeling normally or during HF, we crossed floxed ADGRF5 (ADGRF5^f/f) mice with αMHC-Cre mice to generate cardiomyocyte-specific ADGRF5 knockout mice (CM-ADGRF5-KO), which displayed normal cardiac structure and function at 12 weeks of age versus αMHC-Cre+ control mice, as assessed via echocardiography, gravimetrics and immunohistochemistry. However, CM-ADGRF5-KO mice developed cardiac dysfunction, maladaptive remodeling, and increased mortality over time, even in the absence of pathologic insult, suggesting a homeostatic function of cardiomyocyte-expressed ADGRF5. Further, following TAC surgery, CM-ADGRF5-KO mice displayed an accelerated decline in cardiac function with enhanced remodeling and increased mortality. To attain mechanistic insight into these changes, we performed RNA-sequencing on LV tissue of 12-week-old CM-ADGRF5-KO mice and subsequently validated differential gene targets in isolated left ventricular adult mouse cardiomyocytes (AMCM). We identified <i>Scn1b</i> to be differentially upregulated in CM-ADGRF5-KO AMCM, suggesting altered regulation of sodium currents, whereas overexpression of ADGRF5 in neonatal rat ventricular myocytes (NVRM) resulted in decreased <i>Scn1b</i> expression. Finally, luciferase reporter, fluorescence resonance energy transfer (FRET) and immunoblotting analyses were performed in NRVM, revealing that ADGRF5 proximally signals in a Gαq-dependent manner. In all, these results suggest that ADGRF5 contributes to the maintenance of cardiac health normally and during the development of HF, thus may represent a novel HF therapeutic target. <b>Keywords:</b> GPCRs; Adhesion GPCRs; Cardiomyocytes; Heart Failure