The Cav 1.2 Ca2+ Channel is Expressed in Sarcolemma of Type I and IIA Myofibers of Adult Skeletal Muscle

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Although Ca2+-dependent signaling pathways are important for skeletal muscle plasticity, the sources of Ca2+ that activate these signaling pathways are not completely understood. Influx of Ca2+ through surface membrane Ca2+ channels may activate these pathways. We examined expression of two L-type Ca2+ channels in adult skeletal muscle, the CaV 1.1 and CaV 1.2, with isoform-specific antibodies in Western blots and immunocytochemistry assays. Consistent with a large body of work, expression of the CaV 1.1 was restricted to skeletal muscle where it was expressed in T-tubules. CaV 1.2 was also expressed in skeletal muscle, in the sarcolemma of type I and IIa myofibers. Exercise-induced alterations in muscle fiber types cause a concomitant increase in the number of both CaV 1.2 and type IIa–positive fibers. Taken together, these data suggest that the CaV 1.2 Ca2+ channel is expressed in adult skeletal muscle in a fiber type–specific manner, which may help to maintain oxidative muscle phenotype.