Journal ArticleDOI
Bicarbonate stimulated phospholipid scrambling induces cholesterol redistribution and enables cholesterol depletion in the sperm plasma membrane
Frits M. Flesch,Jos F. Brouwers,Patricia F. E. M. Nievelstein,Arie J. Verkleij,Lambert M.G. van Golde,Ben Colenbrander,Barend M. Gadella +6 more
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TLDR
A model is proposed in which phospholipid scrambling induces the formation of an apical membrane raft in the sperm head surface that enables albumin mediated efflux of cholesterol.Abstract:
Mammalian sperm cells are activated prior to fertilization by high bicarbonate levels, which facilitate lipoprotein-mediated cholesterol efflux. The role of bicarbonate and cholesterol acceptors on the cholesterol organization in the sperm plasma membrane was tested. Bicarbonate induced an albumin-independent change in lipid architecture that was detectable by an increase in merocyanine staining (due to protein kinase A-mediated phospholipid scrambling). The response was limited to a subpopulation of viable sperm cells that were sorted from the non-responding subpopulation by flow cytometry. The responding cells had reduced cholesterol levels (30% reduction) compared with non-responding cells. The subpopulation differences were caused by variable efficiencies in epididymal maturation as judged by cell morphology. Membrane cholesterol organization was observed with filipin, which labeled the entire sperm surface of non-stimulated and non-responding cells, but labeled only the apical surface area of bicarbonate-responding cells. Addition of albumin caused cholesterol efflux, but only in bicarbonate-responding cells that exhibited virtually no filipin labeling in the sperm head area. Albumin had no effect on other lipid components, and no affinity for cholesterol in the absence of bicarbonate. Therefore, bicarbonate induces first a lateral redistribution in the low cholesterol containing spermatozoa, which in turn facilitates cholesterol extraction by albumin. A model is proposed in which phospholipid scrambling induces the formation of an apical membrane raft in the sperm head surface that enables albumin mediated efflux of cholesterol.read more
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Journal ArticleDOI
Metabolism and functions of phosphatidylserine.
Jean E. Vance,Rineke Steenbergen +1 more
TL;DR: In this paper, the authors focus on genes and enzymes involved in PS biosynthesis in bacteria, yeast, plants and mammalian cells and discuss the available information on the regulation of PS biosynthetic in these organisms.
Journal ArticleDOI
Phosphatidylserine and phosphatidylethanolamine in mammalian cells: two metabolically related aminophospholipids.
TL;DR: Cellular levels of PS and PE are tightly regulated by the implementation of multiple compensatory mechanisms, and Elimination of either pathway is embryonically lethal, despite the normal activity of the other pathway.
Journal ArticleDOI
Capacitation Induces Cyclic Adenosine 3′,5′-Monophosphate-Dependent, but Apoptosis-Unrelated, Exposure of Aminophospholipids at the Apical Head Plasma Membrane of Boar Sperm Cells
TL;DR: Bicarbonate-induced phospholipid scrambling appears to be an important and early physiological event in the capacitation process and was a prerequisite for cholesterol relocation in boar spermatozoa.
Journal ArticleDOI
Ion channels, phosphorylation and mammalian sperm capacitation.
TL;DR: Understanding the molecular mechanisms leading to fertilization is central for societies to deal with rising male infertility rates, to develop safe male gamete-based contraceptives and to preserve biodiversity through better assisted fertilization strategies.
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Role of the oviduct in sperm capacitation
TL;DR: In vivo changes in the intra-luminal milieu of the oviduct of pigs and cows are reviewed which relate to the modulation of sperm capacitation around spontaneous ovulation, thus maximizing the chances of normal fertilization.
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TL;DR: Caput epididymal sperm, which lack the ability to undergo capacitation in vitro, do not display this capacitation-dependent subset of tyrosine phosphorylated proteins in complete media even after extended incubation periods, and do not fertilize metaphase II-arrested eggs in vitro.
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