RESUMO
Structural dilation of cardiomyocytes (CMs) imposes a decline in cardiac performance that precipitates cardiac failure and sudden death. Since membrane proteins are implicated in dilated cardiomyopathy and heart failure, we evaluated the expression of the sarcolemmal membrane-associated protein (SLMAP) in dilated cardiomyopathy and its effect on CM contraction. We found that all 3 SLMAP isoforms (SLMAP-1, -2, and -3) are expressed in CMs and are downregulated in human dilated ventricles. Knockdown of SLMAPs in cultured CMs transduced with recombinant adeno-associated viral particles releasing SLMAP-shRNA precipitated reduced spontaneous contractile rate that was not fully recovered in SLMAP-depleted CMs challenged with isoproterenol (ISO), thus phenotypically mimicking heart failure performance. Interestingly, the overexpression of the SLMAP-3 full-length isoform induced a positive chronotropic effect in CMs that was more pronounced in response to ISO insult (vs. ISO-treated naïve CMs). Confocal live imaging showed that H9c2 cardiac myoblasts overexpressing SLMAP-3 exhibit a higher intracellular calcium transient peak when treated with ISO (vs. ISO-treated cells carrying a control adeno-associated viral particle). Proteomics revealed that SLMAP-3 interacts with the regulator of CM contraction, striatin. Collectively, our data demonstrate that SLMAP-3 is a novel regulator of CM contraction rate and their response to adrenergic stimuli. Loss of SLMAPs phenotypically mimics cardiac failure and crystallizes SLMAPs as predictive of dilated cardiomyopathy and heart failure.
Assuntos
Cálcio/metabolismo , Cardiomiopatia Dilatada/metabolismo , Regulação para Baixo , Ventrículos do Coração/metabolismo , Espaço Intracelular/metabolismo , Proteínas de Membrana/metabolismo , Miócitos Cardíacos/metabolismo , Animais , Cardiomiopatia Dilatada/tratamento farmacológico , Cardiomiopatia Dilatada/patologia , Cardiomiopatia Dilatada/fisiopatologia , Linhagem Celular , Regulação para Baixo/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Ventrículos do Coração/efeitos dos fármacos , Humanos , Espaço Intracelular/efeitos dos fármacos , Isoproterenol/farmacologia , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Terapia de Alvo Molecular , Contração Miocárdica/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/patologia , Isoformas de Proteínas/deficiência , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RatosRESUMO
Impaired cardiomyocyte contraction rate is detrimental to cardiac function and often lethal. Despite advancements in the field, there is a paucity of information regarding the coordination of molecules implicated in regulating the heart rate. Striatin (STRN) is a dynamic protein with binding domains to calmodulin (CaM) and caveolin (Cav), both of which are regulators of myocardial function. However, its role in cardiomyocyte contraction is not yet determined. Herein, we show that STRN is expressed in cardiomyocytes and is more abundant in atrial myocardium than in ventricles. Cardiac expression of STRN (protein and mRNA) was developmentally regulated with the highest expression being at neonatal stage (day one) and the lowest in adult rats (13 weeks). CaM pulldown assay indicated that the interaction of cardiac STRN with CaM and caveolin-3 (Cav-3) was calcium sensitive. Interestingly, the overexpression of STRN induced an increase (â¼2-fold) in the rate of the spontaneous contraction of cultured cardiomyocytes, while the knockdown of STRN reduced their contraction rate (â¼40%). The expression level of STRN was inversely proportional to the interaction of Cav-3 with the CaM/STRN complex. Collectively, our data delineate a novel role for STRN in regulating cardiomyocyte spontaneous contraction rate and the dynamics of the STRN/Cav-3/CaM complex.