雄激素调控附睾Psmb8基因表达的分子机制及其生物学意义

附睾缺陷精子的清除与泛素-蛋白酶体通路介导的蛋白质降解有关，具体机制还不清楚。申请者在承担的国家自然科学基金青年项目的研究中发现：抑制小鼠雄激素二氢睾酮的合成可使附睾中缺陷精子增多，蛋白酶体20S催化中心亚基Psmb8基因的转录水平显著下降。我们推测Psmb8基因的表达可能受雄激素的调节，并与附睾中蛋白酶体活性和缺陷精子清除有关。为了验证该假设，本项目拟首先采用体外培养的附睾上皮细胞系研究雄激素及其受体对附睾Psmb8基因表达和蛋白酶体活性的影响；其次采用附睾特异性雄激素受体（AR）基因敲除小鼠模型研究附睾组织中AR对Psmb8基因表达、蛋白酶体活性和缺陷精子数的影响；第三，收集临床上精子畸形率偏高所致不育患者精液标本，检测精子表面泛素水平，分析精子表面泛素水平与缺陷精子数量的关系。结果将对揭示附睾中精子的质量控制机制具有重要的学术意义。

It is known that removal of defective sperm in epididymis is relevant to the ubiquitin-proteasome proteolytic pathway, but its mechanism is still unclear. Our previous studies show that more defective sperms accumulate and expression of Psmb8 gene, one subunit of 20S proteasome catalytic center, is lower in epididymis when synthesis of dihydrotestosterone is inhibited. We presume that the expression of Psmb8 gene can be regulated by androgen and will affect the activity of proteasome and the removal of defective sperm. To verify the hypothesis, firstly, we will study the effect and its mechanism of androgen on the expression of Psmb8 gene and the activity of proteasome in cultured epididymal epithelial cell lines. Secondly, we will study the effect of androgen receptor on the expression of Psmb8 gene, the activity of proteasome and defective sperm content by using epididymis-specific androgen receptor gene knock-out mice model. Finnally, we will collect clinical seminal fluid samples to test ubiquitin levels in sperm surface and analyze the possible correlation between ubiquitin levels in sperm surface and the quantity of defective sperm. Results of this project will help elucidate sperm quality control mechanism.