Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA.
J Cell Physiol. 2010 Sep;224(3):575-80. doi: 10.1002/jcp.22211.
In mammals, the starting point of development is the fusion between sperm and egg. It is well established that sperm fuse with the egg through the equatorial/post-acrosomal region. Apart from this observation and the requirement of two proteins (CD9 in the egg and IZUMO1 in the sperm) very little is known about this fundamental process. Actin polymerization correlates with sperm capacitation in different mammalian species and it has been proposed that F-actin breakdown is needed during the acrosome reaction. Recently, we have presented evidence that actin polymerization inhibitors block the movement of IZUMO1 that accompany the acrosome reaction. These results suggest that actin dynamics play a role in the observed changes in IZUMO1 localization. This finding is significant because IZUMO1 localization in acrosome-intact sperm is not compatible with the known location of the initiation of the fusion between the sperm and the egg. To further understand the actin-mediated changes in protein localization during the acrosome reaction, the distribution of the sperm-specific plus-end actin capping protein CAPZA3 was analyzed. Like IZUMO1, CAPZA3 shows a dynamic pattern of localization; however, these movements follow a different temporal pattern than the changes observed with IZUMO1. In addition, the actin polymerization inhibitor latrunculin A was unable to alter CAPZA3 movement.
在哺乳动物中，发育的起点是精子和卵子的融合。已经证实，精子通过赤道/顶体后区与卵子融合。除了这一观察结果和两种蛋白质（卵子中的 CD9 和精子中的 IZUMO1）的需求外，对于这个基本过程知之甚少。在不同的哺乳动物物种中，肌动蛋白聚合与精子获能相关，并且已经提出顶体反应期间需要 F-肌动蛋白的分解。最近，我们提出的证据表明，肌动蛋白聚合抑制剂阻止了伴随顶体反应的 IZUMO1 的运动。这些结果表明，肌动蛋白动力学在观察到的 IZUMO1 定位变化中起作用。这一发现意义重大，因为顶体完整的精子中 IZUMO1 的定位与已知的精子与卵子融合起始位置不兼容。为了进一步了解顶体反应过程中肌动蛋白介导的蛋白质定位变化，分析了精子特异性加端肌动蛋白盖帽蛋白 CAPZA3 的分布。与 IZUMO1 一样，CAPZA3 显示出动态的定位模式；然而，这些运动遵循与 IZUMO1 观察到的变化不同的时间模式。此外，肌动蛋白聚合抑制剂 latrunculin A 无法改变 CAPZA3 的运动。
