Roles of seminolipid and its binding proteins in male reproduction

了解配子相互作用和配子形成的机制是提高家畜繁殖力的必要条件。由于细胞黏附是精子-卵子相互作用和精子在睾丸中形成的主要机制之一，我们的研究工作长期以来一直投入到这一领域。我们重点研究了一种黏附分子，磺基半乳糖甘油脂(SGG)，它选择性地存在于哺乳动物生殖细胞中，并表明精子表面的SGG参与了精子-卵子(透明带-ZP)的结合。事实上，SGG和它的结合蛋白芳基硫酸酯酶A(ASA)一起作用，也在精子头表面。但由于SGG在精子上大量存在，因此会有更多的SGG结合蛋白参与ZP结合。我们将根据这些蛋白在体外与SGG膜结合的能力来分离它们，然后使用蛋白质组学的方法来获得它们的身份。在同一静脉中，睾丸生殖细胞(TGC)表面的SGG可能与其在支持细胞上的结合蛋白相互作用，支持细胞跨越整个睾丸小管层，在那里从干细胞产生精子。Sertoli细胞对TGCs进行细胞组织，使更高级的TGCs更靠近小管腔。这种支持细胞的功能可能是通过TGC表面SGG和支持细胞表面SGG结合蛋白之间的相互作用来调控的。因此，我们也想要鉴定这些Sertoli细胞表面的SGG结合蛋白。我们进一步证明了两个进化上保守的抗菌肽SPAG11D和SPAG11E存在于人和啮齿动物附睾液中，它们与SGG结合，从而保护精子免受微生物的攻击。这些AMP的大量可用将有助于各种动物的感染治疗。我们最近的结果表明，SPAG11D存在于猪的精浆中；因此，我们将从SPAG11D中纯化天然的SPAG11D，并测试其杀菌活性。我们的研究将深入了解SGG在雄性生殖中的作用，这可能会导致畜牧业生产的改善。

Understanding the mechanisms of gamete interaction and gamete formation is a requirement for fertility enhancement in livestock animals. Since cell adhesion is one main mechanism for both sperm-egg interaction and sperm formation in testes, our research efforts have long been invested in this area. We have focused on an adhesion molecule, sulfogalactosylglycerolipid (SGG), found selectively in mammalian male germ cells, and have shown that sperm surface SGG is involved in sperm-egg vestment (zona pellucida -ZP) binding. In fact, SGG acts together with its binding protein, arylsulfatase A (ASA), also on the sperm head surface. But since SGG exists in abundance on sperm, there would be more SGG binding proteins that participate in ZP binding. We will isolate these proteins based on their ability to bind to SGG membranes in vitro and then use a proteomics approach to obtain their identities. In the same vein, SGG on the testicular germ cell (TGC) surface may interact with its binding proteins on Sertoli cells, which span the whole testicular tubule layer, where sperm are produced from their stem cells. Sertoli cells cyto-organize TGCs, so that the more advanced TGCs are closer to the tubule lumen. This Sertoli cell's function may be orchestrated through the interaction between TGC surface SGG and SGG binding proteins on Sertoli cells. Therefore, we also want to identify these SGG binding proteins on the Sertoli cell surface. We have further shown that two evolutionarily conserved antimicrobial peptides (AMPs), SPAG11D and SPAG11E, present in human and rodent epididymal fluid, bind to SGG and thus protect sperm from microbial attacks. Availability of these AMPs in quantity will be useful for infection treatment in various animals. Our recent results reveal that SPAG11D is present in pig seminal plasma; we will therefore purify the native form SPAG11D and test for its microbicidal activity. Our study will bring insight to the roles of SGG in male reproduction, and this may lead to improved livestock production.