Abou-haila Aïda, Tulsiani Daulat R P
UFR Biomédicale, Université Paris Descartes, Paris Cedex 06, France.
Arch Biochem Biophys. 2009 May 1;485(1):72-81. doi: 10.1016/j.abb.2009.02.003. Epub 2009 Feb 13.
Ejaculated spermatozoa must undergo physiological priming as they traverse the female reproductive tract before they can bind to the egg's extracellular coat, the zona pellucida (ZP), undergo the acrosome reaction, and fertilize the egg. The preparatory changes are the net result of a series of biochemical and functional modifications collectively referred to as capacitation. Accumulated evidence suggests that the event that initiates capacitation is the efflux of cholesterol from the sperm plasma membrane (PM). The efflux increases permeability and fluidity of the sperm PM and causes influx of Ca(2+) ions that starts a signaling cascade and result in sperm capacitation. The binding of capacitated spermatozoa to ZP further elevates intrasperm Ca(2+) and starts a new signaling cascade which open up Ca(2+) channels in the sperm PM and outer acrosomal membrane (OAM) and cause the sperm to undergo acrosomal exocytosis. The hydrolytic action of the acrosomal enzymes released at the site of sperm-egg (zona) binding, along with the hyperactivated beat pattern of the bound spermatozoon, are important factors in directing the sperm to penetrate the ZP and fertilize the egg. The role of Ca(2+)-signaling in sperm capacitation and induction of the acrosome reaction (acrosomal exocytosis) has been of wide interest. However, the precise mechanism(s) of its action remains elusive. In this article, we intend to highlight data from this and other laboratories on Ca(2+) signaling cascades that regulate sperm functions.
射出的精子在穿过雌性生殖道时必须经历生理预激活，之后才能与卵子的细胞外被——透明带（ZP）结合，发生顶体反应并使卵子受精。这些准备性变化是一系列生化和功能修饰的最终结果，这些修饰统称为获能。越来越多的证据表明，引发获能的事件是胆固醇从精子质膜（PM）外流。这种外流增加了精子质膜的通透性和流动性，并导致钙离子内流，从而启动信号级联反应并导致精子获能。获能的精子与透明带结合会进一步提高精子内的钙离子水平，并启动新的信号级联反应，这会打开精子质膜和顶体外膜（OAM）中的钙离子通道，导致精子发生顶体胞吐作用。在精卵（透明带）结合部位释放的顶体酶的水解作用，以及结合精子的超激活摆动模式，是引导精子穿透透明带并使卵子受精的重要因素。钙离子信号在精子获能和顶体反应（顶体胞吐作用）诱导中的作用一直备受关注。然而，其作用的确切机制仍然难以捉摸。在本文中，我们打算重点介绍来自本实验室和其他实验室关于调节精子功能的钙离子信号级联反应的数据。
