Fusion proteins and fusion pores

Sponsored by the Juan March Foundation and organized by R D Burgoyne and G Alvarez de Toledo, Madrid, Spain, May 22–24, 2000.![][1] A meeting was recently held at the Juan March Foundation in Madrid (22–24 May, 2000) on the topic ‘Regulated exocytosis and the vesicle cycle’. This small discussion meeting brought together speakers using molecular, electrophysiological or a combination of approaches in the study of exocytosis and vesicle retrieval. It was clear from the presentations and discussions that there is now reasonable agreement about the key proteins involved in exocytosis, but questions were raised about the roles of other proteins that had previously been implicated in this process but may have other functions. The other major area of discussion related to the existence of a rapidly reversible fusion pore, and the significance of, and possible mechanisms for, ‘kiss‐and‐run’ fusion. Here we highlight some of the emerging ideas and issues that generated discussion at the meeting.### The proteinsThe most generally expressed view was that the so‐called SNARE complex, comprising syntaxin, SNAP‐25 and VAMP, is likely to be the core machinery that drives membrane fusion. Indeed, it was noted that the image of the SNARE complex structure, solved by the groups of Axel Brunger and Reinhard Jahn (Sutton et al ., 1998), almost became the logo of the meeting. One controversial aspect of the SNARE complex, however, has been whether the pairing of a vesicle SNARE with a target membrane SNARE could contribute specificity to vesicle docking. Recently, other mechanisms for vesicle docking have emerged, and SNARE proteins in vitro show highly promiscuous interactions with one another, suggesting that this may not be the case. Richard Scheller (Stanford, CA), however, presented data from permeabilized PC12 cells that revealed a much higher specificity of SNARE interactions in vivo . The assembly of the SNARE complex … [1]: /embed/graphic-1.gif