Dynamics of SNARE assembly and disassembly during sperm acrosomal exocytosis

Gerardo A. De Blas, Carlos M. Roggero, Claudia N. Tomes, Luis S. Mayorga

Research output: Contribution to journalArticle

96 Scopus citations

Abstract

The dynamics of SNARE assembly and disassembly during membrane recognition and fusion is a central issue in intracellular trafficking and regulated secretion. Exocytosis of sperm's single vesicle - the acrosome - is a synchronized, all-or-nothing process that happens only once in the life of the cell and depends on activation of both the GTP-binding protein Rab3 and of neurotoxin-sensitive SNAREs. These characteristics make acrosomal exocytosis a unique mammalian model for the study of the different phases of the membrane fusion cascade. By using a functional assay and immunofluorescence techniques in combination with neurotoxins and a photosensitive Ca2+ chelator we show that, in unactivated sperm, SNAREs are locked in heterotrimeric cis complexes. Upon Ca2+ entry into the cytoplasm, Rab3 is activated and triggers NSF/α-SNAP-dependent disassembly of cis SNARE complexes. Monomeric SNAREs in the plasma membrane and the outer acrosomal membrane are then free to reassemble in loose trans complexes that are resistant to NSF/α-SNAP and differentially sensitive to cleavage by two vesicle-associated membrane protein (VAMP)-specific neurotoxins. Ca2+ must be released from inside the acrosome to trigger the final steps of membrane fusion that require fully assembled trans SNARE complexes and synaptotagmin. Our results indicate that the unidirectional and sequential disassembly and assembly of SNARE complexes drive acrosomal exocytosis.

Original languageEnglish (US)
Article numbere323
Pages (from-to)12P
JournalPLoS biology
Volume3
Issue number10
DOIs
StatePublished - Oct 2005
Externally publishedYes

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Agricultural and Biological Sciences(all)

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