title: Expression of caveolin-3 in skeletal, cardiac, and smooth muscle cells. Caveolin-3 is a component of the sarcolemma and co-fractionates with dystrophin and dystrophin-associated glycoproteins.
abstract: 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, alpha-sarcoglycan, and beta-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.
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142-1479, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Song
authors.forename: P E
authors.initials: PE
authors.lastname: Scherer
authors.forename: Z
authors.initials: Z
authors.lastname: Tang
authors.forename: T
authors.initials: T
authors.lastname: Okamoto
authors.forename: S
authors.initials: S
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Chafel
authors.forename: C
authors.initials: C
authors.lastname: Chu
authors.forename: D S
authors.initials: DS
authors.lastname: Kohtz
authors.forename: M P
authors.initials: MP
authors.lastname: Lisanti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001011:Aorta; D015153:Blotting, Western; D051244:Caveolin 3; D022461:Caveolins; D002460:Cell Line; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D049030:Dystroglycans; D016189:Dystrophin / Q000302:isolation & purification / Q000378:metabolism*; D000939:Epitopes; D005260:Female; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis; D018482:Muscle, Skeletal / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D049031:Sarcoglycans; D012508:Sarcolemma / Q000378:metabolism*; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; C495548:Cav3 protein, mouse; C495549:Cav3 protein, rat; D051244:Caveolin 3; D022461:Caveolins; D003598:Cytoskeletal Proteins; D016189:Dystrophin; D000939:Epitopes; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D049031:Sarcoglycans; D049030:Dystroglycans