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Caveolae are specialized plasma membrane microdomains appearing as 50- to 100-nm vesicular invaginations (1, 2). These organelles were initially identified by Yamada (3) more than 50 yr ago and can be found individually or in clusters at the surface of several cell types, including adipocytes, endothelial cells, fibroblasts, and myocytes. These plasma membrane domains, often referred to as lipid rafts, are rich in cholesterol, glycosphingolipids, and signaling proteins, especially caveolins. Caveolins are major components of the caveolae, and three members of this family (caveolins 1, 2, and 3) have been identified.

There is tissue-specific expression of caveolins. Caveolin-1 (CAV1) is ubiquitously expressed but more so in the adipocytes, endothelial cells, and fibroblasts (4). CAV2 is coexpressed with CAV1 and hetero-oligomerizes with it in many cell types (5). CAV3 expression is more restricted to the myocytes (6). CAV1 gene encodes two isoforms of CAV1, α and β, using two alternate start sites (7). Although CAV1α contains residues 1–178, the β isoform is derived from translation at an alternate start site at an internal methionine at position 32. CAV1 has a transmembrane domain and a W-W (tryptophan-tryptophan) domain for interaction with other proteins. CAV1 is palmitoylated at the cysteine residues at the 133, 143, and 156 positions in the carboxy terminus for cholesterol binding and interaction with other caveolar components (8). The protein is inserted in the membrane in such a way that both its amino and carboxy termini are cytoplasmic.

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