SNAREs in mammalian sperm: Possible implications for fertilization

Soluble N-ethylmalameide-sensitive factor attachment protein receptor (SNAR E) proteins are present in mammalian sperm and could be involved in critica l membrane fusion events during fertilization, namely the acrosome reaction . Vesicle-associated membrane protein/synaptobrevin, a SNARE on the membran e of a vesicular carrier, and syntaxin 1, a SNARE on the target membrane, a s well as the calcium sensor synaptotagmin I, are present in the acrosome o f mammalian sperm (human, rhesus monkey, bull, hamster, mouse). Sperm SNARE s are sloughed off during the acrosome reaction, paralleling the release of sperm membrane vesicles and acrosomal contents, and SNARE antibodies inhib it both the acrosome reaction and fertilization, without inhibiting sperm-e gg binding. In addition, sperm SNAREs may be responsible, together with oth er sperm components, for the asynchronous male DNA decondensation that occu rs following intracytoplasmic sperm injection, an assisted reproduction tec hnique that bypasses normal sperm-egg surface interactions. The results sug gest the participation of sperm SNAREs during membrane fusion events at fer tilization in mammals. (C) 2000 Academic Press.