首页> 外文期刊>Molecular human reproduction. >Regulation of human sperm capacitation by a cholesterol efflux-stimulated signal transduction pathway leading to protein kinase A-mediated up-regulation of protein tyrosine phosphorylation.
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Regulation of human sperm capacitation by a cholesterol efflux-stimulated signal transduction pathway leading to protein kinase A-mediated up-regulation of protein tyrosine phosphorylation.

机译:通过胆固醇外排刺激的信号转导途径调节人精子获能,导致蛋白激酶A介导的蛋白酪氨酸磷酸化上调。

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摘要

Protein tyrosine phosphorylation is an important intracellular event accompanying the in-vitro capacitation of mouse, bovine and human spermatozoa. Here, we demonstrate that bovine serum albumin (BSA) and NaHCO(3) are required for protein tyrosine phosphorylation in ejaculated human spermatozoa. The absence of protein tyrosine phosphorylation in media minus these two constituents could be recovered by addition to the media of cAMP analogues and/or phosphodiesterase inhibitors. Since BSA is postulated to modulate capacitation by removal of cholesterol from the sperm plasma membrane, we determined whether cholesterol release leads to changes in protein tyrosine phosphorylation. Incubation of spermatozoa in media containing BSA resulted in the release of significant amounts of cholesterol when compared with media devoid of BSA. Preloading BSA with cholesterol-SO(4) inhibited protein tyrosine phosphorylation, as well as capacitation, and this inhibitory effect was overcome by the addition of dibutyryl cAMP plus isobutylmethylxanthine (IBMX). The functional significance of BSA-mediated cholesterol release, protein tyrosine phosphorylation and capacitation was confirmed by examining the effects of the cholesterol-binding heptasaccharides, methyl-beta-cyclodextrin or OH-propyl-beta-cyclodextrin. Both cyclodextrins caused cholesterol efflux from the spermatozoa, increased protein tyrosine phosphorylation, and stimulated capacitation. Therefore, cholesterol release is associated with the activation of a signal transduction pathway involving protein kinase A and tyrosine kinase second messenger systems, and resulting in protein tyrosine phosphorylation and capacitation.
机译:蛋白质酪氨酸磷酸化是伴随小鼠,牛和人精子体外获能的重要细胞内事件。在这里,我们证明了牛血清白蛋白(BSA)和NaHCO(3)是射精的人精子中蛋白质酪氨酸磷酸化所必需的。减去这两个成分的培养基中不存在蛋白质酪氨酸磷酸化,可以通过添加到cAMP类似物和/或磷酸二酯酶抑制剂的培养基中来恢复。由于BSA被假定通过从精子质膜上去除胆固醇来调节获能,因此我们确定了胆固醇的释放是否导致蛋白质酪氨酸磷酸化的改变。与不含BSA的培养基相比,在含有BSA的培养基中孵育精子会导致大量胆固醇的释放。用胆固醇-SO(4)预装牛血清白蛋白可抑制蛋白质酪氨酸磷酸化以及获能,这种抑制作用可通过添加二丁酰基cAMP加异丁基甲基黄嘌呤(IBMX)来克服。通过检查与胆固醇结合的七糖,甲基-β-环糊精或OH-丙基-β-环糊精的作用,证实了BSA介导的胆固醇释放,蛋白质酪氨酸磷酸化和获能的功能意义。两种环糊精均导致精子中胆固醇外流,蛋白质酪氨酸磷酸化增加和刺激了获能。因此,胆固醇的释放与涉及蛋白激酶A和酪氨酸激酶第二信使系统的信号转导途径的激活有关,并导致蛋白酪氨酸磷酸化和获能。

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