IHEM   20887
INSTITUTO DE HISTOLOGIA Y EMBRIOLOGIA DE MENDOZA DR. MARIO H. BURGOS
Unidad Ejecutora - UE
artículos
Título:
Membrane-permeant Rab3A triggers acrosomal exocytosis in living human sperm
Autor/es:
LOPEZ, CI; BELMONTE, SA; DE BLAS, GA; MAYORGA, LS
Revista:
FASEB JOURNAL
Editorial:
Bench Press
Referencias:
Año: 2007 vol. 21 p. 4121 - 4130
ISSN:
0892-6638
Resumen:
Abstract The acrosome reaction is a regulated Ca2+-dependent secretion event required for sperm-egg interaction. Previous studies indicate that the process requires Rab3-dependent tethering of membranes, SNARE complex assembly and Ca2+-mediated activation of synaptotagmin. Sperm are transcriptionally and translationally inactive; hence most studies on the exocytosis mechanism are limited to membrane-permeant reagents. The effect of proteins involved in exocytosis has only been assessed in permeabilized cells. Poly-arginine peptides are a powerful tool for delivering macromolecules to cells. Most reports indicate that membrane translocation of arginine-containing proteins requires endocytosis; therefore this strategy might not be useful in sperm. However, our results indicate that GST and Rab3A when fused with an arginine-rich peptide were able to translocate into sperm. Moreover, membrane-permeant Rab3A initiated exocytosis when prenylated and activated with GTP. We show here that a key event after the cytoplasmic Ca2+ increase caused by progesterone is the activation of Rab3A. When active Rab3A is introduced into sperm, Ca2+ in the extracellular medium and in the cytoplasm is dispensable. However, a Ca2+ efflux from inside the acrosome is still required to achieve exocytosis. In conclusion, arginine-containing proteins can penetrate the sperm plasma membrane and are thus valuable tools to study sperm physiology in intact cells.