Regulation of L-type calcium channel by intracellular subunit in cardiac hypertrophy and failure.

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L-type calcium channel (LTCC) localizes at T-tubules and caveolae in cardiomyocytes, and plays major roles in excitation-contraction coupling and cardiac hypertrophy. The expression of b2a subunit of LTCC (b2a) is increased in human failing heart. Phosphorylation of b2a by CaMKII enhanced LTCC activity. In the present study, we examined the pathological role of b2a phosphorylation in cardiac hypertrophy. We developed a method to examine caveolae-specific activation of CaMKII and found that b2a phosphorylation occurs specifically in caveolae and elicit myocyte hypertrophy in a1 adrenergic stimulation. Thus, we generated transgenic mice (TG) overexpressing non phosphorylated mutant of b2a.The expressions of b2a in both mutant and wild-type TG were similar. a1 adrenergic stimulation induced cardiac hypertrophy was attenuated in mutant TG compared to wild-type TG mice. In conclusion, we revealed that phosphorylated b2a localized at caveolae and exaggerates cardiac hypertrophy.