Expression and Subcellular Localization of TRPC3, Orai1, and STIM1 after Pressure Overload-Induced Hypertrophy in Adult Cardiac Myocytes

Abstract

Recent studies have suggested that store-operated Ca2+ entry (SOCE) regulates physiological and pathological cardiac growth. Molecular players identified to contribute to SOCE are TRPC family members and the ORAI1/STIM1 complex found in neonatal cardiomyocytes (CMs). However, whether the expression and subcellular distribution of TRPC3, ORAI1 and STIM1 are changed in adult CMs during the development and progression of hypertrophy, remains unknown.Pressure overload-induced hypertrophy was induced by minimally invasive transverse aortic constriction (TAC) in adult wild-type mice. Sham-operated mice served as controls. Left ventricular tissue homogenates obtained 1, 3, and 6 weeks after TAC were subjected to immunoblotting. Immunocytochemistry was performed in isolated CMs 6 weeks after TAC.TRPC3, ORAI1, and STIM1 were constitutively expressed in Sham and TAC hearts. Co-immunoprecipitation revealed association of STIM1 with ORAI1 and TRPC3. Following TAC, mice developed progressive hypertrophy as evidenced by echocardiographic parameters and gravimetric analysis. In TAC hearts, TRPC3 expression progressively increased (1week: +13±0%; 3weeks: +32±1%; 6weeks: +33±1%), whereas ORAI1 expression decreased (1week: −32±1%; 3weeks: −38±2%; 6weeks: −38±2%) during the progression of hypertrophy. STIM1 expression remained unchanged (n=7). In Sham CMs, TRPC3 was distributed in a striated pattern throughout the cells. ORAI1 was expressed on the plasma membrane and in a striated pattern throughout the cells, with the higher density in the cell periphery. STIM1 appeared in a punctate pattern throughout the cells. In TAC CMs, by contrast, TRPC3 was predominantly found in the cell periphery. ORAI1 and STIM1 subcellular distribution appeared unaffected during pressure overload.In summary, we observed altered expression of TRPC3 and ORAI1 and altered subcellular distribution of TRPC3 in pressure overload-induced hypertrophy in mice. The results raise the possibility that altered SOCE may contribute to the development and/or progression of hypertrophy.