Investigation on a role of Prx4 in spermatogenesis by gene knockout approach

在这项工作中，我们研究了最近发现的抗氧化蛋白Prx4在精子发生中的作用。由于Prx4具有细胞分泌所需的信号序列，因此它被认为在细胞外环境中具有抗氧化剂的功能。然而，它在睾丸中以信号序列完整的前体形式存在。我们假设Prx4参与了精子发生，从精子形成阶段前体形态的巧合出现和形态学分析来判断。首先，我们研究了Prx4在人工隐睾中的表达。虽然分泌型水平没有显著变化，但前体型有选择性地减少。这一结果与Prx4前体参与精子发生的观点一致。睾丸一般在阴囊内，那里的温度比身体其他部位要低一些。这种较低的温度对正常的精子形成是必不可少的。如果隐睾…更多的孩子，睾丸留在腹膜腔，因此，暴露在比正常睾丸更高的温度下。这会导致精子发生障碍。然而，目前尚不清楚究竟是哪种分子参与了这一过程。我们的结果表明，一种处理Prx4前体的酶的活性升高。加工酶活性的异常升高会刺激一种蛋白质的分泌，导致睾丸细胞凋亡，从而导致损伤。我们现在正试图制造缺乏Prx4基因的老鼠。我们进一步研究了在睾丸中起关键作用的谷胱甘肽氧化还原系统。我们发现生精细胞很难合成谷胱甘肽，因为它们对BSO（一种从头合成谷胱甘肽的抑制剂）的敏感性很低。此外，它们没有氧化谷胱甘肽的循环系统，因为谷胱甘肽还原酶没有表达。根据基因表达，似乎支持细胞减少氧化谷胱甘肽，并将其与其他营养和体液因子一起提供给生精细胞。少

In this work, we investigated a role of Prx4, which is recently identified antioxidative protein, in spermatogenesis. Since Prx4 has signal sequence required for secretion from cells, it is assumed to function as an antioxidant in the extracellular milieu. However, it exists as a precursor form with the intact signal sequence in testes. We assume that Prx4 participates in spermatogenesis as judged by coincidental appearance of the precursor form during spermatogenic stage and by morphological analysis.At first, we investigated expression of Prx4 in artificial cryptorchid testes. Although there was no significant alteration in levels of the secreted form, the precursor form was selectively diminished. This result was consistent with the idea that the Prx4 precursor participates in spermatogenesis. Testes are generally in scrotum where temperature is lower in some degrees compared with other parts of body. This lower temperature is essential for normal spermatogenesis. In case of cryptor … More chidism, testes stay in peritoneal cavity and, hence, are exposed to higher temperature than normal testes. This causes impairment in spermatogenesis. However, it is not clear what kind of molecule is actually involved. Our results suggest elevation in activity of an enzyme that processes the Prx4 precursor. Abnormal elevation in activity of the processing enzyme would stimulate secretion of a protein, which induces apoptosis in testis, and result in the impairment. We are now trying to make mice that lack Prx4 gene.We further investigated glutathione redox system that plays a pivotal role in testes. We found that spermatogenic cells hardly synthesize glutathione because they exhibit quite low sensitivity to BSO, an inhibitor for de novo glutathione synthesis. In addition, they do not have recycling system for oxidized glutathione because glutathione reductase is not expressed. Based upon the gene expression, it appears that Sertoli cells reduce back the oxidized glutathione and provide it, together with other nutrition and humoral factors, to spermatogenic cells. Less