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Membrane‐permeant Rab3A triggers acrosomal exocytosis in living human sperm
Author(s) -
Lopez Cecilia I.,
Belmonte Silvia A.,
De Blas Gerardo A.,
Mayorga Luis S.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.06-7716com
Subject(s) - exocytosis , microbiology and biotechnology , endocytosis , sperm , acrosome , acrosome reaction , chemistry , cytoplasm , secretion , biology , biochemistry , cell , botany
The acrosome reaction is a regulated Ca 2+ ‐dependent secretion event required for sperm‐egg interaction. Previous studies indicate that the process requires Rab3‐dependent tethering of membranes, SNARE complex assembly, and Ca 2+ ‐mediated activation of synaptotagmin. Sperm are transcriptionally and translationally inactive; hence, most studies of the exocytosis mechanism are limited to membrane‐per‐meant 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 cytoplas‐mic Ca 2+ increase caused by progesterone is the activation of Rab3A. When active Rab3A is introduced into sperm, Ca 2+ in the extracellular medium and in the cytoplasm is dispensable. However, a Ca 2+ efflux from inside the acrosome is still required to achieve exocy‐tosis. In conclusion, arginine‐containing proteins can penetrate the sperm plasma membrane and thus are valuable tools to study sperm physiology in intact cells.— Lopez, C. I., Belmonte, S. A., De Blas, G. A., Mayorga, L. S. Membrane‐permeant Rab3A triggers acrosomal exocytosis in living human sperm. FASEB J . 21, 4121–4130 (2007)