ENDOTHELIAL CAVEOLAE HAVE THE MOLECULAR-TRANSPORT MACHINERY FOR VESICLE BUDDING, DOCKING, AND FUSION INCLUDING VAMP, NSF, SNAP, ANNEXINS, AND GTPASES

Transport by discrete vesicular carriers is well established at least in part because of recent discoveries identifying key protein mediator s of vesicle formation, docking, and fusion. A general mechanism sensi tive to N-ethylmaleimide (NEM) is required for the transport of a dive rgent group of vesicular carriers in all eukaryotes. Many endothelia h ave an abundant population of noncoated plasmalemmal vesicles or caveo lae, which have been reported with considerable controversy to functio n in transport. We recently have shown that like other vesicular trans port systems, caveolae-mediated endocytosis and transcytosis are inhib ited by MEM (Schnitzer, J. E., Allard, J., and Oh, P. (1995) Am. J. Ph ysiol. 268, H48-H55). Here, we continue this work by utilizing our rec ently developed method for purifying endothelial caveolae from rat lun g tissue (Schnitzer, J. E., Oh, P., Jacobson, B. S., and Dvorak, A. M. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 1759-1763) to show that th ese caveolae contain key proteins known to mediate different aspects o f vesicle formation, docking, and/or fusion including the vSNARE VAMP- 2, monomeric and trimeric GTPases, annexins II and VI, and the NEM-sen sitive fusion factor NSF along with its attachment protein SNAP. Like neuronal VAMPs, this endothelial VAMP is sensitive to cleavage by botu linum B and tetanus neurotoxins. Caveolae in endothelium are indeed li ke other carrier vesicles and contain similar NEM-sensitive molecular machinery for transport.