Membrane lipid dynamics during human sperm capacitation
Abstract
Sperm membranes have an unusual lipidic composition which is distinct from those of mammalian somatic cells. They have high levels of plasmalogens, a kind of ether-linked lipids, and a high content of polyunsaturated fatty acyl groups. Plasmalogens may form non-diffusible membrane regions or domains, whereas polyunsaturated ethanolamine plasmalogens are known to destabilize the lipidic bilayer. During transit of sperm through the female reproductive tract, sperm-coating proteins bind to heparin-like glycosaminoglycans. An essential feature of capacitation is the removal of cholesterol from the acrosomal membrane of sperm. Albumin and high-density lipoproteins present in the uterine and follicular fluid act as cholesterol acceptors. Plasma membrane of sperm organize in large non-diffusible lipid domains. This regionalization affects the distribution of both lipids and proteins. A barrier to lateral diffusion of lipids and proteins in the equatorial segment has been reported and contributes to the formation of macrodomains. Lateral separation into cholesterol-rich and cholesterol-depleted microdomains could also be created. Cone-shaped phospholipids induce the formation of non-bilayer phases and might facilitate membrane fusion. ...Continue Reading
Citations
Expression of cystatin C in the female reproductive tract and its effect on human sperm capacitation
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