Membrane-permeant Rab3A triggers acrosomal exocytosis in living human sperm.
FASEB J
; 21(14): 4121-30, 2007 Dec.
Article
en En
| MEDLINE
| ID: mdl-17625073
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 of the exocytosis mechanism are limited to membrane-permeant reagents. The effect of proteins involved in exocytosis has been assessed only in permeabilized cells. Polyarginine 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 thus are valuable tools to study sperm physiology in intact cells.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Espermatozoides
/
Acrosoma
/
Permeabilidad de la Membrana Celular
/
Proteína de Unión al GTP rab3A
/
Exocitosis
Límite:
Animals
/
Female
/
Humans
/
Male
Idioma:
En
Revista:
FASEB J
Asunto de la revista:
BIOLOGIA
/
FISIOLOGIA
Año:
2007
Tipo del documento:
Article
País de afiliación:
Argentina
Pais de publicación:
Estados Unidos