Receptor-activated phospholipase D is present in caveolin-3-enriched lightmembranes of C2C12 myotubes

Caveolin-3 (cav-3) is a key structural component of caveolar membrane in sk eletal muscle. Cav-3-enriched light membrane (CELM) fractions obtained from C2Cl2 myotubes contain phospholipase D1 (PLD1) and its major regulators, R hoA and protein kinase C alpha (PKC alpha). All these proteins were found b ound to cav-3. An in vivo assay of PLD activity, which allows to localize t he reaction product in CELMs, indicated that the enzyme associated to this membrane microdomain was active. Moreover, bradykinin (BK), thrombin and ph orbol 12-myristate 13-acetate induced rapid stimulation of PLD activity in CELMs. The cav-3-PLD1 complex was not affected by BK treatment, whereas the agonist induced a marked increase of RhoA association with cav-3. Furtherm ore, BK-induced PLD activation in CELMs was dependent, at least in part, on PKC alpha. (C) 2000 Federation of European Biochemical Societies.