A Second Protein Marker of Caveolae：Caveolin-2

Caveolin-2,a protein about 20 kD,is a major component of the inner surface of caveolae,small invaginations of the plasma membrane.Similar with caveolin-1 and caveolin-3,it serves as a protein marker of caveolae.Caveolin-1 and-2 are located next to each other at 7q31.1 on human chromosome,the proteins encoded are co-localized and form a stable hetero-oligomeric complex,distributing similarly in tissue and cultured cells.Caveolin-3 is located on different chromosomes but confirmed to interact with caveolin-2.Caveolin-2 is similar to caveolin-1 in many respects but differs from the latter in functional domains,especially in G-protein binding domain and caveolin scaffolding domain.The mRNAs of both caveolin-1 and caveolin-2 are most abundantly expressed in white adipose tissue and are induced during differentiation of 3T3-L1 cells to adipocytes.Caveolin-2-deficinet mice demonstrate clear pulmonary defects,with little or no change in caveolin-1 expression and caveolae formation,suggesting that caveolin-2 plays a selective role in lung functions.Caveolin-2 is also involved in lipid metabolism and human cancers.