POTENTIAL ROLE FOR HEXOKINASE IN SPERM/EGG INTERACTION

哺乳动物受精的最初事件是 有受精能力的雄配子和雌配子(精子和卵子， )。在精子发生和附睾成熟过程中， 精子的质膜变得能够与 卵子的细胞外基质，即透明带。这个精子-卵子 相互作用是物种特有的，并导致顶体的诱导 最终成功受精所必需的反应。这些 相互作用具有配体-受体-效应器的许多特征 调节许多体细胞功能的相互作用。而当 与精子质膜结合的透明带成分已经被 被证明是一种名为ZP3的鸡蛋特异性糖蛋白，它是一种 精子膜仍不清楚。许多候选的ZP3受体具有 建议包括MR的一个主要的含磷酸酪氨酸的蛋白 九万五千美元。最近，这种蛋白质已经被提纯，并被证明是一种独特的 膜结合、酪氨酸磷酸化形式的糖酵解酶 己糖激酶。克隆研究结果表明，精子中可能含有 多种形式的己糖激酶，其中一些类似于体细胞 而且其中一些似乎是生精细胞所独有的。这个 这项提议的长期目标是检查这种己糖激酶 在精子与卵子的相互作用中起着重要作用。具体目标是：1) 确定成熟精子中存在哪种异构体(S)己糖激酶 它的位置；具体地说，是否有任何异构体定位于精子 覆盖在顶体上的膜，精子-卵子相互作用的部位，2)到 确定己糖激酶的哪一种亚型(S)在酪氨酸上被磷酸化 成熟精子中的残留物及其形成机制 磷酸化的，即自动磷酸化事件和/或通过 酪氨酸激酶，以及3)确定成熟精子中的己糖激酶 参与精子-透明带的相互作用；具体地说，可以 这种相互作用可以用干扰己糖激酶的探针来抑制。 在健康方面，这些实验的结果将促进 对精子-卵子结合和相互作用有更深入的了解。此外，这些 实验可能导致新的避孕方法和一种 对特殊形式的不孕症的理解。

The initial event of mammalian fertilization is the interaction of fertilization-competent male and female gametes (the sperm and egg, respectively). During spermatogenesis and epididymal maturation, the plasma membrane of the sperm becomes capable of binding to the extracellular matrix of the egg, the zona pellucida. This sperm-egg interaction is species-specific and leads to the induction of the acrosome reaction which is ultimately required for successful fertilization. These interactions have many characteristics of ligand-receptor-effector interactions which regulate numerous somatic cell functions. While the zona pellucida component that binds to the sperm plasma membrane has been shown to be an egg-specific glycoprotein called ZP3, the receptor on the sperm membrane remains unknown. A number of candidate ZP3 receptors have been suggested including a major phosphotyrosine-containing protein of Mr 95,000. Recently, this protein has been purified and shown to be a unique membrane-bound, tyrosine-phosphorylated form of the glycolytic enzyme hexokinase. Results of cloning studies suggest that sperm may contain multiple forms of hexokinase, some of which are similar to the somatic forms and some of which appear to be unique to spermatogenic cells. The long-term objective of this-proposal is to examine whether this hexokinase in sperm has a role in sperm-egg interaction. The specific aims are: 1) to determine which isoform(s) of hexokinase is present in mature sperm and its location; specifically, whether any isoform localizes to the sperm membrane overlying the acrosome, the site of sperm-egg interaction, 2) to determine which isoform(s) of hexokinase is phosphorylated on tyrosine residues in the mature sperm and the mechanism by which it becomes phosphorylated, i.e. an autophosphorylation event and/or by the action of a tyrosine kinase, and 3) to determine whether hexokinase in mature sperm participates in the sperm-zona pellucida interaction; specifically, can this interaction be inhibited with probes that interfere with hexokinase. In relation to health the results from these experiments will promote a deeper understanding of sperm-egg binding and interaction. Moreover, these experiments may lead to new approaches to contraception and to a comprehension of specific forms of infertility.