Cholesterol content regulates acrosomal exocytosis by enhancing Rab3A plasma membrane association

S. A. Belmonte, C. I. López, C. M. Roggero, G. A. De Blas, C. N. Tomes, L. S. Mayorga

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

The acrosome is an exocytic granule that overlies the spermatozoan nucleus. In response to different stimuli, it undergoes calcium-regulated exocytosis. Freshly ejaculated mammalian sperm are not immediately capable of undergoing acrosome reaction. The acquisition of this ability is called capacitation and involves a series of still not well-characterized changes in the sperm physiology. Plasma membrane cholesterol removal is one of the sperm modifications that are associated with capacitation. However, how sterols affect acrosomal exocytosis is unknown. Here, we show that short incubations with cyclodextrin, a cholesterol removal agent, just before stimulation promote acrosomal exocytosis. Moreover, the effect was also observed in permeabilized cells stimulated with calcium, indicating that cholesterol plays a direct role in the calcium-dependent exocytosis associated with acrosome reaction. Using a photo-inhibitable calcium chelator, we show that cholesterol affects an early event of the exocytic cascade rather than the lipid bilayers mixing. Functional data indicate that one target for the cholesterol effect is Rab3A. The sterol content does not affect the Rab3A activation-deactivation cycle but regulates its membrane anchoring. Western blot analysis and immunoelectron microscopy confirmed that cholesterol efflux facilitates Rab3A association to sperm plasma membrane. Our data indicate that the cholesterol efflux occurring during capacitation optimizes the conditions for the productive assembly of the fusion machinery required for acrosome reaction.

Original languageEnglish (US)
Pages (from-to)393-408
Number of pages16
JournalDevelopmental Biology
Volume285
Issue number2
DOIs
StatePublished - Sep 15 2005
Externally publishedYes

Keywords

  • Acrosome reaction
  • Calcium
  • Cholesterol
  • Exocytosis
  • Membrane fusion
  • Methyl-β-cyclodextrin
  • Rab3A
  • Spermatozoa

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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