Mastoparan induces Ca2+-independent cortical granule exocytosis in sea urchin eggs

• Published in: Biochemical and biophysical research communications 2003-01, Vol.301 (1), p.13-16
• Main Authors: López-Godínez, Juana, Garambullo, Teresa I, Martínez-Cadena, Guadalupe, García-Soto, Jesús
• Format: Article
• Language: English
• Subjects: Animals; Calcium - metabolism; Chelating Agents - metabolism; Egtazic Acid - analogs & derivatives; Egtazic Acid - metabolism; Exocytosis - drug effects; Exocytosis - physiology; Female; Male; Membrane Fusion - physiology; Oocytes - drug effects; Oocytes - physiology; Peptides; Sea Urchins - physiology; Spermatozoa - metabolism; Wasp Venoms - chemistry; Wasp Venoms - pharmacology
• ISSN: 0006-291X
• DOI: 10.1016/S0006-291X(02)02979-0

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.