Mastoparan induces Ca2+-independent cortical granule exocytosis in sea urchin eggs.
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.
López-Godínez
Juana
J
Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, P.O. Box 187, Guanajuato, Gto. 36000, Mexico.
Garambullo
Teresa I
TI
Martínez-Cadena
Guadalupe
G
García-Soto
Jesús
J
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005260:Female; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008561:Membrane Fusion / Q000502:physiology; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology; D010455:Peptides; D012617:Sea Urchins / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism; D014862:Wasp Venoms / Q000737:chemistry / Q000494:pharmacology*
D002614:Chelating Agents; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; D004533:Egtazic Acid; C037500:mastoparan; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium