Cardiomyocyte survival and death contributes to many cardiac diseases. A common mechanism of cardiomyocyte death is through apoptosis however, numerous death receptors (DR) have been virtually unstudied in the context of cardiovascular disease. Previous studies have identified TNF-related apoptosis inducing ligand (TRAIL) and its receptor, DR5, as being altered in a chronic catecholamine administration model of heart failure, and suggest a role of non-canonical signaling in cardiomyocytes. Furthermore, multiple clinical studies have identified TRAIL or DR5 as biomarkers in the prediction of severity and mortality following myocardial infarction and in heart failure development risk suggesting a role of DR5 signaling in the heart. While TRAIL/DR5 have been extensively studied as a potential cancer therapeutic due to their ability to selectively activate apoptosis in cancer cells, TRAIL and DR5 are highly expressed in the heart where their function is uncharacterized. However, many non-transformed cell types are resistant to TRAIL-induced apoptosis suggesting non-canonical functions in non-cancerous cell types. Our goal was to determine the role of DR5 in the heart with the hypothesis that DR5 does not induce cardiomyocyte apoptosis but initiates non-canonical signaling to promote cardiomyocyte growth and survival. Histological analysis of hearts from mice treated with a DR5 agonists showed increased hypertrophy with no differences in cardiomyocyte death, fibrosis or function. Mechanistic studies in the heart and isolated cardiomyocytes identified ERK1/2 activation with DR5 agonist treatment which contributed to hypertrophy. Furthermore, epidermal growth factor receptor (EGFR) was activated following DR5 agonist treatment through activation of MMP and HB-EGFR cleavage and specific inhibitors of MMP and EGFR prevented DR5-mediated ERK1/2 signaling and hypertrophy. Taken together, these studies identify a previously unidentified role for DR5 in the heart, which does not promote apoptosis but acts through non-canonical MMP-EGFR-ERK1/2 signaling mechanisms to contribute to cardiomyocyte hypertrophy.
Keywords: Death receptor 5; EGFR transactivation; ERK1/2; Hypertrophy.
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