Sperm plasma membrane

About: Sperm plasma membrane is a research topic. Over the lifetime, 1016 publications have been published within this topic receiving 49964 citations.

Molecular aspects of mammalian fertilization

Abstract: The initial communication between the gametes is a molecular, receptor-mediated process that takes place at the surface of the egg coat. The zona pellucida plays a central role in this process such that, on the one hand, spermatozoa may bind to it and, on the other hand, it prevents polyspermy. In the mouse, ZP3, a glycoprotein of the zona pellucida with a mol. wt of 84 kd, serves as a sperm receptor. Only a relatively small part of ZP3, namely certain O-linked carbohydrate side chains, is involved in the process of binding. These oligosaccharides probably become bound to enzymes associated with the plasma membrane of the sperm head and thus form an enzyme-substrate complex. A terminal alpha-galactose has been found to be one of the decisive sugar molecules and, moreover, the critical chemical group. After sperm binding to the zona pellucida has taken place, the polypeptide chain of ZP3 initiates the acrosome reaction in the sperm head. In the mouse, numerous binding proteins have been detected in the sperm plasma membrane: these are enzymes such as glycosyl transferases, proteinases, and glycosidases. A galactosyl transferase has been found on the surface of the mouse sperm that binds specifically to N-acetylglucosamine in the mouse zona pellucida. It is therefore apparent that carbohydrate-binding proteins on the sperm surface mediate gamete recognition through their high affinity and specificity for complex glycoconjugates in the egg coat. In fact, it is not at all surprising that complementary cell-surface protein and glycoconjugates are involved in fertilization, since many somatic cells exhibit a similar mechanism of cell recognition.

Measuring ion fluxes in sperm.

Abstract: Publisher Summary The chapter discusses different strategies to study ion fluxes in sperm. Ion channels and transporters in the sperm plasma membrane participate crucially in fertilization. Ion-permeability changes are deeply involved in how sperm sense environmental cues and signals from the outer envelope of the egg to achieve fertilization. Combining the in vivo measurements of intracellular ions and membrane potential in sperm populations and single cells with electrophysiological approaches, such as the smart patch-clamp, and reconstitution strategies in planar bilayers reveal how sperm ion channels participate in sperm motility and the acrosome reaction. This chapter describes ion transport protocols for sea urchin sperm. Egg ligands immediately induce sperm responses. It is important to measure the rapid kinetics of their responses to understand the underlying signaling mechanisms. To perform a successful time-resolved measurement, it is essential that sperm be exposed to egg ligands as rapidly as possible. There are two different methods to achieve this: (1) rapid mixing (stopped-flow fluorometry) and (2) photolysis of caged (photoactivatable) ligands. The chapter presents techniques used in the study of ion fluxes in single sea urchin sperm.

Effect of Butylated Hydroxytoluene Supplementation in Extender on Motility, Plasmalemma and Viability of Sahiwal Bull Spermatozoa

Abstract: This experiment was designed to evaluate the effect of butylated hydroxytoluene supplementation in extender on motility, plasmalemma and viability of Sahiwal bull spermatozoa. Semen was collected from three Sahiwal bulls of similar age group with artificial vagina for three weeks (replicates). Qualifying semen ejaculates were split into five aliquots and cryopreserved in tris-citric extender having either 0.0 (control), 0.5, 1.0, 2.0 or 3.0mM butylated hydroxytoluene. After thawing at 37°C, semen was evaluated for sperm motility, plasma membrane integrity and viability. Sperm plasma membrane integrity was assessed using supravital hypo-osmotic swelling test, while viability was assessed with dual staining procedure using Trypan blue and Giemsa stain. Sperm motility, plasma membrane integrity and viability were higher in extender containing 0.5mM butylated hydroxytoluene compared to the control and extenders containing 1.0, 2.0 and 3.0mM butylated hydroxytoluene. It is concluded that supplementation of 0.5mM butylated hydroxytoluene in tris-citric acid extender improved the motility, plasma membrane integrity and viability of Sahiwal bull spermatozoa.

Subcellular localization of β1,4-galactosyltransferase on bull sperm and its function during sperm–egg interactions

Abstract: The process of sperm–oocyte recognition is a complex interaction between the plasma membrane of sperm and the extracellular matrix of the oocyte. The best studied mammalian system is the mouse, in which sperm plasma membrane receptors recognize specific oligosaccharides on the egg coat glycoprotein ZP3. A well-defined ZP3 receptor on mouse sperm is β1,4-galactosyltransferase (GalT). In this study, we investigated the possibility that GalT is present on bull sperm, and that it may participate during bovine sperm–oocyte binding. Using Western immunoblotting, bull sperm were found to have a protein of molecular weight similar to mouse GalT at ∼60 kDa. Immunogold low voltage scanning electron microscopy reveals that GalT epitopes are confined to the anterior cap of fresh or capacitated bull sperm. To investigate the function of bovine sperm GalT, fresh bull sperm were pretreated with either preimmune or anti-GalT antibody and added to in vitro-matured bovine oocytes. Sperm exposed to preimmune serum fertilized 82.7% (153 of 185) of the oocytes, whereas sperm exposed to anti-GalT antiserum fertilized only 42.3% (202 of 478) of the oocytes. We determined whether the inhibition of fertilization resulted from a direct inhibition of sperm–oocyte binding. The number of sperm bound to eggs was determined by low voltage scanning electron microscopy following pretreatment with preimmune or anti-GalT antibody. An average of 25.3 ± 2.2 (mean ± SEM) sperm bound per half-oocyte when treated with preimmune serum. In contrast, exposure of sperm to anti-GalT antiserum significantly lowered (P < 0.001) the frequency of sperm binding to 9.9 ± 0.8 bound per half-oocyte. These results show that GalT is present on the anterior cap of the bovine sperm head, where it participates in fertilization by facilitating sperm–oocyte binding. The function of GalT in both the murine and bovine systems suggests that it may serve as a generalized gamete receptor in mammals. Mol. Reprod. Dev. 58:236–244, 2001. © 2001 Wiley-Liss, Inc.