Caveolae-localized L-type Ca²⁺ channels do not contribute to function or hypertrophic signalling in the mouse heart

L-type Ca²⁺ channels (LTCCs) in adult cardiomyocytes are localized to t-tubules where they initiate excitation-contraction coupling. Our recent work has shown that a subpopulation of LTCCs found at the surface sarcolemma in caveolae of adult feline cardiomyocytes can also generate a Ca²⁺ microdomain that activates nuclear factor of activated T-cells signaling and cardiac hypertrophy, although the relevance of this paradigm to hypertrophy regulation in vivo has not been examined.

Here we generated heart-specific transgenic mice with a putative caveolae-targeted LTCC activator protein that was ineffective in initiating or enhancing cardiac hypertrophy in vivo. We also generated transgenic mice with cardiac-specific overexpression of a putative caveolae-targeted inhibitor of LTCCs, and while this protein inhibited caveolae-localized LTCCs without effects on global Ca²⁺ handling, it similarly had no effect on cardiac hypertrophy in vivo. Cardiac hypertrophy was elicited by pressure overload for 2 or 12 weeks or with neurohumoral agonist infusion. Caveolae-specific LTCC activator or inhibitor transgenic mice showed no greater change in nuclear factor of activated T-cells activity after 2 weeks of pressure overload stimulation compared with control mice.

Our results indicate that LTCCs in the caveolae microdomain do not affect cardiac function and are not necessary for the regulation of hypertrophic signaling in the adult mouse heart.