DE-NOVO FORMATION OF CAVEOLAE IN LYMPHOCYTES BY EXPRESSION OF VIP21-CAVEOLIN

Caveolae are plasma membrane invaginations, which have been implicated in endothelial transcytosis, endocytosis, potocytosis, and signal tra nsduction. In addition to their well-defined morphology, caveolae are characterized by the presence of an integral membrane protein termed V IP21-caveolin. We have recently observed that lymphocytes have no dete ctable VIP21-caveolin and lack plasma membrane invaginations resemblin g caveolae. Here we transiently express VIP21-caveolin in a lymphocyte cell line using the Semliki Forest virus expression system and show d e novo formation of plasma membrane invaginations containing VIP21-cav eolin. These invaginations appear homogeneous in size and morphologica lly indistinguishable from caveolae of nonlymphoid cells, Moreover, th e glycosylphosphatidylinositol-anchored protein Thy1, patched by antib odies, redistributes to the newly formed caveolae, Our results show th at VIP21-caveolin is a key structural component required for caveolar biogenesis.