Figure 1

Structure and general activities of caveolae/caveolin-1. Structure (box): caveolae are flask-shaped invaginations in the cell membrane coated with multimers of caveolin scaffolding proteins. The N-termini and C-termini of caveolin proteins are in the cell cytoplasm, but a hairpin loop of the protein is inserted into the cell membrane. Caveolin-1 has a caveolin scaffolding domain (CSD) that can bind to and affect the activity of a variety of cell signaling molecules. Activities: various caveolae/caveolin-1 activities that have been reported in different cell types are depicted. Caveolin-1 binds to cholesterol and can regulate mitochondrial levels of cholesterol. Caveolae are rich cholesterol stores as well as membrane reservoirs that can stretch to buffer mechanical and osmotic stress at the cell surface. Caveolin-1 can regulate cellular levels of nitric oxide (NO) through regulation of NO synthase activity. Caveolin-1 can inhibit cell growth and activate cell senescence by inhibition of mitogen-activated protein (MAP) kinases and binding to the p53 inhibitor MdM2. Caveolin-1 can also regulate other growth and differentiation signaling pathways by caveolar endocytosis of cell surface receptors and sequestering secondary messengers such as β-catenin. Caveolin-1 also participates in focal adhesion signaling and internalization of integrins upon cell detachment. For references, see main text. BMP, bone morphogenetic protein; MLC, myosin light chain; PI-3-kinase, phosphatidylinositol 3-kinase; TGFβ, transforming growth factor beta.