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  • Title: Mastoparan induces Ca2+-independent cortical granule exocytosis in sea urchin eggs.
    Author: López-Godínez J, Garambullo TI, Martínez-Cadena G, García-Soto J.
    Journal: Biochem Biophys Res Commun; 2003 Jan 31; 301(1):13-6. PubMed ID: 12535633.
    Abstract:
    In most species, cortical granule exocytosis is characteristic of egg activation by sperm. It is a Ca(2+)-mediated event which results in elevation of the vitelline coat to block permanently the polyspermy at fertilization. We examined the effect of mastoparan, an activator of G-proteins, on the sea urchin egg activation. Mastoparan was able to induce, in a concentration-dependent manner, the egg cortical granule exocytosis; mastoparan-17, an inactive analogue of mastoparan, had no effect. Mastoparan, but not sperm, induced cortical granule exocytosis in eggs preloaded with BAPTA, a Ca(2+) chelator. In isolated egg cortical lawns, which are vitelline layers and membrane fragments with endogenously docked cortical granules, mastoparan induced cortical granule fusion in a Ca(2+)-independent manner. By contrast, mastoparan-17 did not trigger fusion. We conclude that in sea urchin eggs mastoparan stimulates exocytosis at a Ca(2+)-independent late site of the signaling pathway that culminates in cortical granule discharge.
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