Elucidation of MURC-mediated mechanisms of caveolae function and transportsome formation in cardiomyocytes

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Immunoelectron microscopy revealed that MURC was expressed in caveolae and T tubules in cardiomyocytes, and transmission electron microscopy showed that caveolae were retained in cardiomyocytes of MURC-knockout (KO) mice. Alpha-1 adrenergic receptor (AR) stimulation-induced ERK activation and cardiac hypertrophy were attenuated in MURC-KO mice compared with wild-type mice. Upon alpha-1-AR stimulation, both MURC and phosphorylated ERK were translocated from the plasma membrane to the perinuclear region in cardiomyocytes. Immunoprecipitation revealed that MURC was associated with phosphorylated and total ERK. These findings suggest that MURC is dispensable for caveolar formation in cardiomyocytes, and that MURC serves as an ERK-recruiting protein in the caveolae within cardiomyocytes. The recruiting function of MURC is necessary to elicit efficient signaling of the alpha-1-AR/ERK cascade in the caveolae in cardiac hypertrophy.