Expression of Caveolin-3 in Skeletal, Cardiac, and Smooth Muscle Cells

• Published in: The Journal of biological chemistry Vol. 271; no. 25; pp. 15160 - 15165
• Main Authors: Song, Kenneth S., Scherer, Philipp E., Tang, ZhaoLan, Okamoto, Takashi, Li, Shengwen, Chafel, Mark, Chu, Caryn, Kohtz, D. Stave, Lisanti, Michael P.
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 01-06-1996
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.25.15160

Caveolae are microdomains of the plasma membrane that have been implicated in signal transduction. Caveolin, a 21–24-kDa integral
membrane protein, is a principal component of the caveolae membrane. Recently, we and others have identified a family of caveolin-related
proteins; caveolin has been retermed caveolin-1. Caveolin-3 is most closely related to caveolin-1, but caveolin-3 mRNA is
expressed only in muscle tissue types. Here, we examine (i) the expression of caveolin-3 protein in muscle tissue types and
(ii) its localization within skeletal muscle fibers by immunofluorescence microscopy and subcellular fractionation. For this
purpose, we generated a novel monoclonal antibody (mAb) probe that recognizes the unique N-terminal region of caveolin-3,
but not other members of the caveolin gene family. A survey of tissues and muscle cell types by Western blot analysis reveals
that the caveolin-3 protein is selectively expressed only in heart and skeletal muscle tissues, cardiac myocytes, and smooth
muscle cells. Immunolocalization of caveolin-3 in skeletal muscle fibers demonstrates that caveolin-3 is localized to the
sarcolemma (muscle cell plasma membrane) and coincides with the distribution of another muscle-specific plasma membrane marker
protein, dystrophin. In addition, caveolin-3 protein expression is dramatically induced during the differentiation of C2C12
skeletal myoblasts in culture. Using differentiated C2C12 skeletal myoblasts as a model system, we observe that caveolin-3
co-fractionates with cytoplasmic signaling molecules (G-proteins and Src-like kinases) and members of the dystrophin complex
(dystrophin, α-sarcoglycan, and β-dystroglycan), but is clearly separated from the bulk of cellular proteins. Caveolin-3 co-immunoprecipitates
with antibodies directed against dystrophin, suggesting that they are physically associated as a discrete complex. These results
are consistent with previous immunoelectron microscopic studies demonstrating that dystrophin is localized to plasma membrane
caveolae in smooth muscle cells.