Structural mechanisms and evolution of egg-sperm interactions

 描述(申请人提供)：自20世纪80年代以来，不孕不育的发病率增加了4%，其中高达20%的病例原因不明。普遍的假设之一是同源卵子和精子蛋白之间不相容；然而，在任何生物体中都很少发现相互作用的生殖蛋白对。研究受精的最佳模型仍然是海产腹足类鲍鱼，受精的第一步之一涉及精子蛋白赖氨酸与其卵壳受体VERL之间的相互作用。作为鲍鱼卵衣的主要成分，VERL是一种巨大的纤维状糖蛋白，由~22ZP-N重复组成，形成分子间氢键，形成高度稳定和保护的卵衣。赖氨酸通过竞争氢键在卵子外壳上制造了一个洞，允许精子通过并与卵母细胞融合。VERL重复序列与人类卵壳蛋白同源，可能具有相似的蛋白质拓扑结构。然而，驱动卵壳溶解的确切结构机制仍有待确定。为了解决受精中的这个基本问题，提出了使用最先进的结构和蛋白质组学方法的两个具体目标。在目标1中，将使用多维核磁共振来表征三种鲍鱼赖氨酸-VERL相互作用的结构基础。在目标2中，将利用深度突变扫描来探索赖氨酸和VERL获得的允许物种特异性相互作用的特定适应，并同时测试性选择的理论模型。这项拟议的研究具有创新性，它结合使用蛋白质组学和结构技术来表征快速进化的生殖蛋白质的进化史。这些结果有望深入了解鲍鱼卵子-精子相互作用的核心机制，并为理解更复杂的哺乳动物系统提供基础信息。

 DESCRIPTION (provided by applicant): The incidence of infertility has increased 4% since the 1980s, with up to 20% cases having no known cause. One of the prevailing hypotheses is incompatibility between cognate egg and sperm proteins; however, very few pairs of interacting reproductive proteins have been identified in any organism. The best model for studying fertilization remains the marine gastropod abalone, where one of the first steps in fertilization involves the interaction between the sperm protein lysin and its egg coat receptor VERL. As a major component of the abalone egg coat, VERL is a giant, fibrous glycoprotein composed of ~22 ZP-N repeats that form intermolecular hydrogen bonds to create the highly stabilized and protective egg coat. Lysin creates a hole in the egg coat by competing for the hydrogen bonds, allowing sperm to pass and fuse with the oocyte. The VERL repeats are homologous to human egg coat proteins, and likely share a similar protein topology. However, the precise structural mechanisms that drive egg coat dissolution remains to be determined. To address this fundamental question in fertilization, two specific aims are proposed using state-of-the-art structural and proteomic approaches. In aim 1, multidimensional NMR will be used to characterize the structural basis of lysin-VERL interactions for three species of abalone. In aim 2, deep mutational scanning will be utilized to explore the specific adaptations acquired by lysin and VERL that permit species specific interactions, and simultaneously test theoretical models of sexual selection. The proposed research is innovative for its combined use of proteomic and structural techniques to characterize the evolutionary history of rapidly evolving reproductive proteins. The results are expected to shed insight into the core mechanisms that mediate egg-sperm interactions in abalone, and provide foundational information towards understanding the more complex mammalian system.