Molecular and Cellular Aspects of Mammalian Sperm Acrosomal Exocytosis

STIVAL, CINTIA; LA SPINA, FLORENCIA A.; BUFFONE,M.G.; DARIO KRAPF

: Animal Models and Human Reproduction: Cell and Molecular Approaches with Reference to Human Reproduction

WILEY-BLACKWELL PUBLISHING, INC

Año: 2017; p. 409 - 419

After ejaculation, mammalian sperm perform a maturational process called capacitation. During capacitation, sperm activate a complex cascade of signaling pathways leading to acquire two essential features: the development of hyperactivated motility and the ability to undergo acrosomal exocytosis upon stimulation with the proper stimuli. Mammalian sperm must undergo acrosomal exocytosis to penetrate the extracellular matrix surrounding the egg, named zona pellucida (ZP). Following exocytosis, the posterior region of the acrosome, known as the equatorial segment, engages in membrane fusion with the oocyte (Moore and Bedford, 1978; Oura and Toshimori, 1990; Wassarman, 1987). A critical protein for sperm?egg fusion is IZUMO1, which is localized on the acrosomal membrane. As a consequence of acrosomal exocytosis, this protein relocalizes to the surface of the equatorial region, and sperm become fusion competent (Satouh et al., 2012; Sosnik et al., 2009, 2010). Acrosomal exocytosis shares many molecular mechanisms in common with other cellular secretory processes. However, there are some features that make this process a special type of regulated secretion: (i) a single exocytotic granule per cell is involved; (ii) there is no membrane recycling; and (iii) rather than a single vesicle?plasma membrane union point, fusion between the outer acrosomal and the plasma membranes occurs at multiple sites to destabilize the structure of the acrosome (Mayorga et al., 2007).