Caveolin-3 at the T-tubule Colocalizes with α-actinin in the Adult Murine Cardiac Muscle

Abstract

Caveolin-3 is thought to serve as a structural and a scaffolding protein in the caveolae of striated muscle. The present study aims to clarify the precise localization of caveolin-3 and its interactive protein partners in adult murine cardiac muscle by immunohistochemistry, immunoblot and immunoprecipitation. Double labeling confocal images showed that caveolin-3 is colocalized with dihydropyridine receptor α1, ryanodine receptor, and α-actinin, but not sarcoplasmic or endoplasmic reticulum calcium ATPase 2. Immunoelectron microscopy demonstrated that caveolin-3 is localized at the T-tubules. Subsequently, we investigated the protein interaction between caveolin-3 and α-actinin, a major component of the Z-band, using immunoprecipitation and immunoblot. It was of interest to note that caveolin-3 was coprecipitated with α-actinin in cardiac muscle extraction but not in skeletal muscle. Taken together, these data indicate that caveolin-3 serves as a mediator between sarcomeric dynamics via the Z-bands and T-tubule function in cardiac muscle.