Deubiquitinating Enzymes as Targets for Male Contraception

 描述(申请人提供)：这个项目的中心目标是鉴定和表征泛素特异肽酶51(USP51)的小分子抑制剂，USP51是一种精子特有的去泛素化(DUB)酶，作为开发可逆的、非激素的男性避孕药的一种手段。泛素系统是确保哺乳动物细胞内蛋白质周转的基础。泛素激活酶、泛素偶联酶和泛素蛋白连接酶催化泛素分子与蛋白质的结合，这是一个将泛素分子定位于蛋白酶体进行降解的过程。DUBS催化去除泛素，以促进它们的回收利用。我们已经鉴定出USP51在晚期伸长的精子细胞和附睾精子中特异表达。在使用Vivo-Morpholinos的小鼠中，USP51的耗尽会导致男性不育，这是因为完全阻断了精子的活力。我们的总体假设是，USP51是一个可行的避孕靶点，自然界中存在的或实验室中修饰的小分子将有效且可逆地抑制附睾精子中USP51的功能。我们将追求以下具体目标来解决这一假设：1)验证USP51作为避孕开发的有效策略的靶向性。2)筛选硅胶和体外小分子文库，鉴定HIT化合物。3)执行Hit-to-Lead药物化学优化，并评估精子、睾丸和动物对候选药物的暴露效果和可逆性。这些研究将促进我们对精子发生和精子功能的基本了解，并为开发可逆地抑制关键精子酶的新避孕药提供可能性。

 DESCRIPTION (provided by applicant): The central goal of this project is to identify and characterize small molecule inhibitors of Ubiquitin specific peptidase 51 (USP51), a deubiquitinating (DUB) enzyme exclusive to sperm, as a means to develop a reversible, non-hormonal male contraceptive. The ubiquitin system is fundamental to ensure protein turnover within mammalian cells. Ubiquitin-activating enzymes, ubiquitin-conjugating enzymes, and ubiquitin protein ligases catalyze the attachment of ubiquitin molecules to proteins, a process that targets them to the proteasome for degradation. DUBs catalyze the removal of ubiquitin to facilitate their recycling. We have identified USP51 to be specifically expressed in late elongating spermatids and epididymal sperm. USP51 depletion in mice using Vivo-Morpholinos results in male infertility due to a complete block of sperm motility. Our overall hypothesis is tat USP51 is a viable contraceptive target and that small molecules existing in nature or modified in the laboratory will effectively and reversibly inhibit USP51 function in epididymal sperm. We will pursue the following Specific Aims to address this hypothesis: 1) Validate the targeting of USP51 as an effective strategy for contraceptive development. 2) Screen small molecule libraries in silico and in vitro to identify hit compounds. 3) Perform hit-to-lead medicinal chemistry optimization and assess the exposure of sperm, testes and animals to candidates for efficacy and reversibility. These studies will advance our basic understanding of spermatogenesis and sperm function, as well as provide the potential for developing new contraceptive agents that reversibly inhibit a critical sperm enzyme.