Cardiac Gab1 deletion leads to dilated cardiomyopathy associated with mitochondrial damage and cardiomyocyte apoptosis

Abstract

A vital step in the development of heart failure is the transition from compensatory cardiac hypertrophy to decompensated dilated cardiomyopathy (DCM) during cardiac remodeling under mechanical or pathological stress. However, the molecular mechanisms underlying the development of DCM and heart failure remain incompletely understood. In the present study, we investigate whether Gab1, a scaffolding adaptor protein, protects against hemodynamic stress-induced DCM and heat failure. We first observed that the protein levels of Gab1 were markedly reduced in hearts from human patients with DCM and from mice with experimental viral myocarditis in which DCM developed. Next, we generated cardiac-specific Gab1 knockout mice (Gab1-cKO) and found that GabcKO mice developed DCM in hemodynamic stress-dependent and age-dependent manners. Under transverse aorta constriction (TAC), Gab1-cKO mice rapidly developed decompensated DCM and heart failure, whereas Gab1 wild-type littermates exhibited adaptive left ventricular hypertrophy without changes in cardiac function. Mechanistically, we showed that Gab1-cKO mouse hearts displayed severe mitochondrial damages and increased cardiomyocyte apoptosis. Loss of cardiac Gab1 in mice impaired Gab1 downstream MAPK signaling pathways in the heart under TAC. Gene profiles further revealed that ablation of Gab1 in heart disrupts the balance of anti-and pro-apoptotic genes in cardiomyocytes. These results demonstrate that cardiomyocyte Gab1 is a critical regulator of the compensatory cardiac response to aging and hemodynamic stress. These findings may provide new mechanistic insights and potential therapeutic target for DCM and heart failure. The progression of heart failure is associated with cardiac remodeling, the changes of cardiac structure and function in response to various stress conditions such as pressure overload-generated hemodynamic stress and agingassociated oxidative stress. 1 Under hemodynamic stress, the heart undergoes a stage of compensated hypertrophy and then progresses into decompensated dilated cardiomyopathy (DCM) and heart failure. 2 Cardiac hypertrophy is an adaptive, regulatory process, in which activation of cardiomyocyte survival pathways maintains cardiac homeostasis against external stress. During the transition from compensatory hypertrophy to DCM, cardiomyocyte death plays a critical role in development of heart failure. [3][4][5][6] However, the molecular mechanisms for controlling the balance of cell survival and cell death during cardiac remodeling remain poorly understood.The Grb2-associated binder 1 (Gab1) is a member of the insulin receptor substrate-like multi-substrate docking protein family and expressed in various types of cells, including cardiomyocytes. [7][8][9] It is a central mediator of growth factor receptor signaling. 10,11 Gab1 is phosphorylated by tyrosine kinases, and then phosphorylated Gab1 recruits and activates phosphatidylinositol 3-kinase (PI3K)/Akt and protein tyrosine phosphatase SHP2 (PTPN11)/mitogen-activated protein kinase (MAPK...

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