Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States of America.
Department of Biology, University of Washington Seattle, WA, United States of America.
PLoS Genet. 2020 Dec 30;16(12):e1009217. doi: 10.1371/journal.pgen.1009217. eCollection 2020 Dec.
A unifying feature of polycystin-2 channels is their localization to both primary and motile cilia/flagella. In Drosophila melanogaster, the fly polycystin-2 homologue, Amo, is an ER protein early in sperm development but the protein must ultimately cluster at the flagellar tip in mature sperm to be fully functional. Male flies lacking appropriate Amo localization are sterile due to abnormal sperm motility and failure of sperm storage. We performed a forward genetic screen to identify additional proteins that mediate ciliary trafficking of Amo. Here we report that Drosophila homologues of KPC1 and KPC2, which comprise the mammalian KIP1 ubiquitination-promoting complex (KPC), form a conserved unit that is required for the sperm tail tip localization of Amo. Male flies lacking either KPC1 or KPC2 phenocopy amo mutants and are sterile due to a failure of sperm storage. KPC is a heterodimer composed of KPC1, an E3 ligase, and KPC2 (or UBAC1), an adaptor protein. Like their mammalian counterparts Drosophila KPC1 and KPC2 physically interact and they stabilize one another at the protein level. In flies, KPC2 is monoubiquitinated and phosphorylated and this modified form of the protein is located in mature sperm. Neither KPC1 nor KPC2 directly interact with Amo but they are detected in proximity to Amo at the tip of the sperm flagellum. In summary we have identified a new complex that is involved in male fertility in Drosophila melanogaster.
多囊蛋白-2 通道的一个统一特征是它们定位于初级纤毛和运动性纤毛/鞭毛。在黑腹果蝇中，果蝇多囊蛋白-2 同源物 Amo 是精子发生早期的内质网蛋白，但该蛋白最终必须在成熟精子的鞭毛尖端聚集才能充分发挥功能。由于精子运动异常和精子储存失败，缺乏适当的 Amo 定位的雄性果蝇不育。我们进行了正向遗传筛选，以鉴定其他介导 Amo 纤毛运输的蛋白质。在这里，我们报告说，果蝇同源物 KPC1 和 KPC2，它们构成了哺乳动物 KIP1 泛素化促进复合物（KPC），形成了一个保守的单元，该单元对于 Amo 的精子尾部尖端定位是必需的。缺乏 KPC1 或 KPC2 的雄性果蝇表现出与 amo 突变体相同的表型，并且由于精子储存失败而不育。KPC 是一种异二聚体，由 E3 连接酶 KPC1 和衔接蛋白 KPC2（或 UBAC1）组成。与它们的哺乳动物对应物一样，果蝇 KPC1 和 KPC2 物理相互作用，并在蛋白质水平上稳定彼此。在果蝇中，KPC2 被单泛素化和磷酸化，这种修饰形式的蛋白位于成熟精子中。KPC1 和 KPC2 都不直接与 Amo 相互作用，但它们在精子鞭毛的尖端与 Amo 接近。总之，我们已经鉴定出一个新的复合物，该复合物参与了黑腹果蝇的雄性生育能力。
