Bicarbonate Induces Membrane Reorganization and CBR1 and TRPV1 Endocannabinoid Receptor Migration in Lipid Microdomains in Capacitating Boar Spermatozoa
Bicarbonate Induces Membrane Reorganization and CBR1 and TRPV1 Endocannabinoid Receptor Migration in Lipid Microdomains in Capacitating Boar Spermatozoa
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DOI：
10.1007/s00232-010-9316-8
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发表时间：
2010-12-01
影响因子：
2.4
通讯作者：
Barboni, Barbara
中科院分区：
文献类型：
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作者：
Botto, Laura;Bernabo, Nicola;Barboni, Barbara
哺乳动物的精子只有在被称为“获能”的形态功能成熟后才能获得充分的受精能力。在这一过程中，存在于女性上生殖道或培养基中的高水平碳酸氢盐诱导了精子膜的显著重组，其特征是双相行为：在几分钟内，它促进了膜磷脂的初步混乱，并在2-4小时后，使精子能够在白蛋白介导的胆固醇提取后识别透明带。本研究表明，在无蛋白培养基中与碳酸氢盐孵育的精子，通过在蔗糖密度梯度上进行超离心分离的抗洗涤剂膜组分（DRM）中存在的脂质微域发生了显著的重组。事实上，与射精精子（未暴露的精子[nES]细胞）相比，碳酸氢盐暴露的精子（ES）细胞显示出蛋白质DRM含量的增加，特别是Cav-1和CD55（小泡和脂筏的标记物）以及顶体外膜（OAM）的标记物顶蛋白-2的含量增加。此外，在ES获得的DRM中，参与获能的某些蛋白质，如内源性大麻素系统受体大麻素受体1型（CBR1）和瞬时受体电位阳离子通道1 （TRPV1）的数量增加。这些数据使我们能够假设，即使在没有细胞外蛋白的情况下，精子膜重组也会发生；除了质膜外，OAM也参与了这一过程；而内源性大麻素受体TRPV1和CBR1等在内向外信号传导中起关键作用的重要分子也参与了这一事件，对精子功能有潜在的重要影响。
Mammalian spermatozoa acquire full fertilizing ability only after a morphofunctional maturation called "capacitation." During this process the high level of bicarbonate present within the upper female genital tract or in culture medium induces a marked reorganization of sperm membranes characterized by a biphasic behavior: In a few minutes, it promotes membrane phospholipid scrambling preliminary to the apical translocation of sterol that, 2-4 h later, enables spermatozoa to recognize zona pellucida after albumin-mediated cholesterol extraction. In the present research it was demonstrated that spermatozoa incubated with bicarbonate in protein-free media underwent a marked reorganization of lipid microdomains present in a detergent-resistant membrane fraction (DRM) isolated by ultracentrifugation on sucrose density gradient. In fact, bicarbonate exposed sperm (ES) cells, compared with ejaculated spermatozoa (nonexposed sperm [nES] cells), displayed an increase in protein DRM content and, in particular, in Cav-1 and CD55, markers of caveolae and lipid rafts, as well in acrosin-2, a marker of the outer acrosomal membrane (OAM). Moreover, the amount of certain proteins involved in capacitation, such as the endocannabinoid system receptors cannabinoid receptor type 1 (CBR1) and transient receptor potential cation channel 1 (TRPV1), increased in DRM obtained from ES. These data allow us to hypothesize that sperm membrane reorganization takes place even in the absence of extracellular proteins; that not only the plasma membrane but also the OAM participate in this process; and that important molecules playing a key role in inside-out signaling, such as the endocannbinoid receptors TRPV1 and CBR1, are involved in this event, with potentially important consequences on sperm function.