A Rho-signaling pathway mediates cortical granule translocation in the sea urchin oocyte.
Cortical granules are secretory vesicles of the egg that play a fundamental role in preventing polyspermy at fertilization. In the sea urchin egg, they localize directly beneath the plasma membrane forming a compact monolayer and, upon fertilization, undergo a Ca(2+)-dependent exocytosis. Cortical granules form during early oogenesis and, during maturation, translocate from the cytosol to the oocyte cortex in a microfilament-mediated process. We tested the hypothesis that these cortical granule dynamics were regulated by Rho, a GTPase of the Ras superfamily. We observed that Rho is synthesized early in oogenesis, mainly in a soluble form. At the end of maturation, however, Rho associates with cortical granules. Inhibition of Rho with the C3 transferase from C. botulinum blocks cortical granule translocation and microfilaments undergo a significant disorganization. A similar effect is observed by GGTI-286, a geranylgeranyl transferase inhibitor, suggesting that the association of Rho with the cortical granules is indispensable for its function. In contrast, the anchorage of the cortical granules in the cortex, as well as their fusion at fertilization, are Rho-independent processes. We conclude that Rho association with the cortical granules is a critical regulatory step in their translocation to the egg cortex.
Covián-Nares
Fernando
F
Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Col. Noria Alta, Guanajuato, Gto 3600, A.P. 187, Mexico.
Martínez-Cadena
Guadalupe
G
López-Godínez
Juana
J
Voronina
Ekaterina
E
Wessel
Gary M
GM
García-Soto
Jesús
J
D036002:ADP Ribose Transferases / Q000494:pharmacology; D008841:Actin Cytoskeleton / Q000378:metabolism; D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D007120:Immunochemistry; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008540:Meiosis; D009865:Oocytes / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D009866:Oogenesis; D012617:Sea Urchins / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism*; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
C437105:GGTI 286; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins; D007930:Leucine