Structuresandfunctionsofthespermubiquitin-proteasomesystem involvedlnfertilizationandreproduction

我们先前报道，泛素-蛋白酶体系统(UPS)在受精过程中起着关键的胞外作用，在罗氏海鞘和肠囊中，UPS是一种卵衣裂解素，允许精子穿透卵壳。然而，精子UPS的结构特征和分选机制尚不清楚。在这里，我们使用这些海鞘研究了精子特异性UPS。我们发现，某些泛素结合酶(Ube2r)在肠囊线虫的睾丸中特异表达，精子20S蛋白酶体α6/PSMA1亚基的C-末端16个残基是在罗氏梭子虫中特异加工的。这些发现使我们能够进一步研究蛋白酶体的C末端处理可能参与蛋白酶体到精子头部区域顶体或外表面的分选。

We previously reported that the ubiquitin-proteasome system(UPS) plays a key extracellular role in fertilization, as an egg-coat lysin, which allows sperm to penetrate through the egg-coat in the ascidians H. roretziand C. intestinalis. However, the structural features and the sorting mechanism of the sperm UPS are not known. Here, we investigated the sperm-specific UPS using these ascidians. We found that a certain ubiquitin-conjugating enzyme(Ube2r) is specifically expressed in the testis of C. intestinalis and that the C-terminal 16 residues of theα6/PSMA1 subunit of the sperm 20S proteasome are specifically processed in H. roretzi. These findings enabled us to further investigate the possible involvement of the C-terminal processing of the proteasome in the sorting of the proteasome to an acrosome or outer surface of sperm head regions.