Molecules involved in acrosomal exocytosis and cortical granule exocytosis
At fertilization, the acrosome reaction and cortical reaction are crucial process to block polyspermy and the prevention of triploidy. Although molecules involved in trigger secretion are various in different exocytosis events, the two processes may share the similar exocytosis mechanism. Exocytosis is an accurate regulated process that consists of multiple stages such as recruitment, targeting, tethering and docking of secretory vesicles with the plasma membrane, priming of the fusion machinery and calcium-triggered membrane fusion. After fusion, the membrane around the secretory vesicle is incorporated into the plasma membrane and the granule releases its contents. The proteins involved in these processes belong to several highly conserved families: Rab GTPases, SNAREs (soluble NSF-attachment protein receptors), α-SNAP (α-NSF attachment protein), NSF (N-ethylmaleimide-sensitive factor), Munc13, Munc18, complexins and synaptotagmins. This review discussed that molecules believed to participate in the secretory function and their involvement in acrosome and cortical granule exocytosis.