Rab3A triggers cortical granule exocytosis in mouse eggs

MICHAUT, MARCELA A.; LÓPEZ, CECILIA; CARABAJAL, MARIANELA; MAYORGA, LUIS SEGUNDO

Rosario, Santa Fe, Argentina

Congreso; Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

Cortical granule (CG) exocytosis in the egg is one of most important steps, which occurs after sperm-egg fusion at fertilization. CG exocytosis, which is induced by the spermatozoon, plays a role in blocking polyspermy. Induction of CG exocytosis depends on intracellular calcium mobilization; however little is known about the signal transduction pathway downstream of calcium mobilization. Rab3A, a member of the small GTP-binding protein family, has been implicated in exocytosis regulated by calcium. In mouse egg, Rab3A is specifically distributed at the cortical region where CGs are localized; nevertheless it is unknown if Rab3A has a role in CG exocytosis in mouse eggs. In order to investigate the effect of Rab3A in intact cells, we have designed a membrane permeant by adding a polyarginine peptide (R) at the N terminus of Rab3A (R-Rab3A) and we tested the effect of R-Rab3A in CG exocytosis. Metaphase II eggs were incubated in presence of either A23187, a calcium ionophore, or R-Rab3A. Then, CG were fixed, visualized by staining luminal glycoproteins with FITC-Lens Culinaris Agglutinin, and quantified using Image J program. We found that R-Rab3A stimulated CG exocytosis in the same extent that the calcium ionophore A23187. These results show that Rab3A participates in CG exocytosis signal transduction pathway in mouse eggs.