Lipid changes of goat sperm plasma membrane during epididymal maturation
TL;DR: The altered lipid profile of the mature sperm membrane leads to changes in its fluidity that play an important role in determining the structure and functions of the biomembrane.
About: This article is published in Biochimica et Biophysica Acta.The article was published on 1991-01-30. It has received 76 citations till now. The article focuses on the topics: Sperm plasma membrane & Membrane lipids.
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TL;DR: It is shown that HSL is required for spermatogenesis but is not the only enzyme that mediates the hydrolysis of triacylglycerol stored in adipocytes, and that adipocytes were significantly enlarged and the size differences between cell and tissue suggests the heterogeneity of adipocytes.
Abstract: Hormone-sensitive lipase (HSL) is known to mediate the hydrolysis not only of triacylglycerol stored in adipose tissue but also of cholesterol esters in the adrenals, ovaries, testes, and macrophages. To elucidate its precise role in the development of obesity and steroidogenesis, we generated HSL knockout mice by homologous recombination in embryonic stem cells. Mice homozygous for the mutant HSL allele (HSL−/−) were superficially normal except that the males were sterile because of oligospermia. HSL−/− mice did not have hypogonadism or adrenal insufficiency. Instead, the testes completely lacked neutral cholesterol ester hydrolase (NCEH) activities and contained increased amounts of cholesterol ester. Many epithelial cells in the seminiferous tubules were vacuolated. NCEH activities were completely absent from both brown adipose tissue (BAT) and white adipose tissue (WAT) in HSL−/− mice. Consistently, adipocytes were significantly enlarged in the BAT (5-fold) and, to a lesser extent in the WAT (2-fold), supporting the concept that the hydrolysis of triacylglycerol was, at least in part, impaired in HSL−/− mice. The BAT mass was increased by 1.65-fold, but the WAT mass remained unchanged. Discrepancy of the size differences between cell and tissue suggests the heterogeneity of adipocytes. Despite these morphological changes, HSL−/− mice were neither obese nor cold sensitive. Furthermore, WAT from HSL−/− mice retained 40% of triacylglycerol lipase activities compared with the wild-type WAT. In conclusion, HSL is required for spermatogenesis but is not the only enzyme that mediates the hydrolysis of triacylglycerol stored in adipocytes.
560 citations
407 citations
TL;DR: 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.
293 citations
Cites background from "Lipid changes of goat sperm plasma ..."
...(1) Severe modifications in the lipid composition take place during this process, including a decrease in cholesterol (Rana et al., 1991; Haidl and Opper, 1997)....
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TL;DR: It was found that the He1 homolog is a major cholesterol-binding protein in the porcine epididymal fluid and the possibility that the HE1 homology is involved in the regulation of the lipid composition of the sperm membranes during the maturation in epidIDymis is discussed.
199 citations
TL;DR: In common mammals, sperm leaving the testis are incapable of fertilizing a female gamete, and when assessing sperm maturation it is necessary to establish the proportion of sperm that has completed and retained all steps of maturation necessary to achieve fertilization of oocytes under the conditions imposed.
Abstract: In common mammals, sperm leaving the testis are incapable of fertilizing a female gamete. Sperm have limited biosynthetic capability and need to minimize demand for ATP. Hence, modification of sperm to achieve their maturation requires pre-programmed cleavage of integral molecules (planned self-modification) and remodelling by action of molecules found in the suspending fluids. Most of these biocatalysts are secreted by a series of specialized regions in the epididymal epithelium, but some are provided in seminal plasma. The role of the epididymis in sperm maturation is postulated to be 'setting a series of triggers' each capable of initiating cellular changes either at emission or near or in the oocyte, and 'setting a safety' for each trigger to prevent premature occurrence of the event. The attributes required in a spermatozoon for in vitro fertilization and natural mating are different, and their expression is dependent on the site of sperm sampling. Some attributes needed for fertility are probably like an on-off switch, whereas others probably allow a gradually reduced probability of success before going to the off position (analogous to a conventional light switch and a dimmer-type light switch). All essential attributes of a spermatozoon must be expressed in a 'combined effective amount' for that cell to be fertile. Because of mixing, in any segment of the epididymal duct the population of sperm is heterogeneous in age and biological status. Thus, when assessing sperm maturation it is necessary to establish the proportion of sperm that has completed and retained all steps of maturation necessary to achieve fertilization of oocytes under the conditions imposed. In a normal animal, most sperm leaving the epididymis have a 'combined effective amount' of attributes, and the population has a high fertilizing potential.
191 citations
References
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TL;DR: The composition of phospholipids extracted from bovine testicular, epididymal and ejaculated spermatozoa was examined and there was little alteration in composition of the various aldehyde components.
96 citations
TL;DR: The phospholipid composition of spermatozoa from the latter region of the epididymis more closely resembled ejaculated spermatoza, while the concentration of total phospholIPid, phosphatidylcholine, and choline plasmalogen in spermatoZoa from the caput epidIDymis of the ram was higher than in the cauda.
Abstract: The concentration of total phospholipid, phosphatidylcholine, phosphatidylethanolamine, and choline plasmalogen in spermatozoa from the caput epididymis of the ram was higher than in spermatozoa from the cauda The phospholipid composition of spermatozoa from the latter region of the epididymis more closely resembled ejaculated spermatozoa
83 citations
TL;DR: New data presented here show that the cow, rabbit and cat produce Type 1, whereas the dog, mouse, guinea pig and baboon produce Type 2 diesters, suggesting a biogenetic relation between the two types of compounds.
Abstract: The literature is surveyed on two types of diester lipid that occur on the skin surfaces of animals: Type 1, a hydroxy fatty acid of which the hydroxyl group and the carboxyl group are esterified respectively with another fatty acid and a fatty alcohol, and Type 2, and alkane α,β-diol of which each OH group is esterified with a fatty acid. New data presented here show that the cow, rabbit and cat produce Type 1, whereas the dog, mouse, guinea pig and baboon produce Type 2 diesters. Each occurs as a major component of the surface lipid. The homologue distribution is given for Type 1 diesters of cow, rabbit and cat as well as the Type 2 diesters of dog and mouse. Distribution of long chain fatty acids of Type 1 diesters parallels that of the fatty alcohols suggesting a biogenetic relation between the two types of compounds. GLC of total diesters for the cow suggests that the components are assembled randomly during biosynthesis. Molecular weight of these diesters are in the range of those of natural triglycerides composed mainly of C16 and C18 fatty acids.
76 citations
TL;DR: The ether lipids may provide stable structural components of sperm membrane while the diacyl analogs undergo degradation and resynthesis, and be the major labeled lipids in sperm lipids.
71 citations