Critical Role of αB Crystalline on Stretch‐Induced FAK Activation in Cardiomyocytes

Abstract

AimFocal adhesion kinase (FAK) is activated and plays a role in cardiomyocyte hypertrophy induced by mechanical stress. FAK activation may depend on cooperation with protein partners. We investigated whether interaction with alpha‐B crystalline (αB Crys) regulates FAK activation by mechanical stress in cardiomyocytes.MethodsαB Crys and FAK expression and phosphorylation at Tyr397 (pFAK) were quantified in neonatal rat ventricular myocytes (NRVMs). FAK/αB Crys interaction was investigated by co‐immunoprecipitation and pulldown assays. αB Crys depletion by RNAi was used to examine its effect on FAK activation.ResultsCyclic stretch (10%, 2 hs) increased pFAK (2‐fold) and enhanced αB Crys expression (4‐fold) and phosphorylation at Ser59 (3‐fold). Stretch also induced FAK/αB Crys association. Pulldown assays with recombinant FAK domains indicated that the interaction with αB Crys is mediated by FAK C‐terminal domain. FAK immunostaining was coincident with myofilaments in non‐stretched while in stretched cells it was predominantly located in the nuclei. αB Crys was predominantly located at the nuclei of stretched NRVMs, coincident with FAK staining. Depletion of αB Crys markedly reduced FAK activation and re‐location to the nucleus.ConclusionThis study demonstrates that αB Crys associates and regulates FAK activation in cardiomyocytes in response to mechanical stress.