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1 July 2004 Cholesterol Efflux Alters Lipid Raft Stability and Distribution During Capacitation of Boar Spermatozoa
Sadaf Shadan, Peter S. James, Elizabeth A. Howes, Roy Jones
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Abstract

A reduction in plasma membrane cholesterol is one of the early events that either triggers or is closely associated with capacitation of mammalian spermatozoa. In this investigation, we have examined the effects of cholesterol efflux on tyrosine phosphorylation, lipid diffusion, and raft organization in boar spermatozoa. Results show that a low level of cholesterol efflux, mediated by 5 mM methyl-β-cyclodextrin (MBCD), enhances capacitation and induces phosphorylation of two proteins at 26 and 15 kDa without affecting sperm viability. Lipid diffusion rates under these conditions are largely unaffected except when cholesterol efflux is excessive. Low-density Triton X100-insoluble complexes (lipid rafts) were isolated from spermatozoa and found to have a restricted profile of proteins. Capacitation-associated cholesterol efflux has no effect on raft composition, but cholesterol depletion destabilizes them completely and phosphorylation is suppressed. During MBCD-mediated capacitation, the distribution of GM1 gangliosides on spermatozoa changes in a sequential manner from overlying the sperm tail to clustering on the sperm head. It is concluded that there is a safe window for removal of plasma membrane cholesterol from spermatozoa within which protein phosphorylation and polarized migration of lipid rafts take place. A preferential loss of cholesterol from the nonraft pool may be the stimulus that promotes raft clustering over the anterior sperm head.

Sadaf Shadan, Peter S. James, Elizabeth A. Howes, and Roy Jones "Cholesterol Efflux Alters Lipid Raft Stability and Distribution During Capacitation of Boar Spermatozoa," Biology of Reproduction 71(1), 253-265, (1 July 2004). https://doi.org/10.1095/biolreprod.103.026435
Received: 10 December 2003; Accepted: 1 March 2004; Published: 1 July 2004
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KEYWORDS
gamete biology
in vitro fertilization
sperm capacitation
sperm maturation
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