Figure 5.

The exocytotic fate of a Syt-bearing dense-core vesicle. (A) A vesicle is shown that has yet to fuse or has already fused and undergone endocytosis (i.e., from B to A). Syt-7’s N terminus is exposed to the vesicle lumen; the C2 domains are exposed to the cytosol. (B) Membrane depolarization and Ca²⁺ influx lead to fusion and fusion pore formation. To trigger entry into this state, the C2A (blue) and C2B (red) might both penetrate the plasma membrane (Bai and Chapman, 2004) or the C2A and C2B might interact with opposing vesicle and plasma membranes (Herrick et al., 2009). (C) The early fusion pore widens. Continued lipid association of the C2 domains may slow the expansion of the fusion pore (Bendahmane et al., 2018). (D) The C2 domains release the plasma membrane as the fusion pore expands.