MARCKS participates in cortical granule exocytosis in mouse eggs

GALLO GIOVANNA LUCRECIA; DE PAOLA MARIA MATILDE; MAYORGA LUIS SEGUNDO; MICHAUT MARCELA ALEJANDRA

San Luis

Congreso; XLVII Reunión Anual de la Sociedad de Investigación en Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Cortical granule (CG) exocytosis is a secretory process that blocks polyspermy and enables successful embryonic development. Nevertheless, the molecular mechanism of this particular exocytosis remains unknown. We have reported that MARCKS, a prominent substrate of PKC involved in exocytosis in different cell types, is expressed in mouse eggs. We hypothesized that MARCKS is involved in cortical granule exocytosis. To test this hypothesis, we, first, analyzed the colocalization of MARCKS and CG by confocal microscopy during mouse oocyte maturation and egg activation, and, second, microinjected GST-MARCKS effector domain to analize MARCKS function in a functional assay of CG exocytosis. During oocyte maturation, confocal microscopy results showed that MARCKS localized uniformly in the cytoplasm of germinal vesicle oocytes; however, in metaphase II eggs, its localization was mainly associated to the cortical region, which is enriched in CG. During egg activation, CG exocytosis was associated with a dramatic decrease in MARCKS staining. Microinjection experiments showed that only the microinjection of GST-MARCKS effector domain was able to inhibit CG exocytosis stimulated by SrCl2 when compared to control, and this inhibition was  concentration-dependent. Our data suggest that MARCKS is involved in the signal transduction pathways that lead to cortical granule exocytosis in mouse eggs.