Qu Fei, Ying Xiaoqian, Guo Wei, Guo Qiangsu, Chen Guowu, Liu Yue, Ding Zhide
Shanghai Key Laboratory for Reproductive Medicine, Department of Histology and Embryology, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
Reproduction. 2007 Oct;134(4):569-76. doi: 10.1530/REP-07-0145.
Sperm motility is essential for male reproduction or natural fertilization. The cyclic AMP (cAMP)/cAMP-dependent protein kinase A (PKA) signaling pathway is generally recognized as one of the significant signaling pathways in the regulation of mammalian spermatozoan motility. Since Zn-alpha2-glycoprotein (ZAG) activity in mammalian adipose tissue is mediated via the beta(3)-adrenoreceptor, with upregulation of the cAMP pathway, we hypothesize that ZAG may play the same role in sperm motility regulation, a new factor of regulation of sperm motility. Therefore, the gene encoding human ZAG was cloned and polyclonal antibodies were generated, and then laser scanning confocal microscopy and flow cytometry were employed to identify this protein in human spermatozoa. The results showed that ZAG protein was mostly localized on the pre-equatorial region covering the acrosome, neck, and middle piece of the flagellum of spermatozoa. Furthermore, using computer-assisted sperm analysis, we found that anti-human ZAG antibodies could significantly reduce the motility of human swim-up spermatozoa after 90- or 120-min incubation (P<0.05 and P<0.01 respectively), together with the decreasing of intracellular cAMP and PKA levels. In conclusion, these data suggest that ZAG is present in human spermatozoa and may be involved in the regulation of sperm motility via the cAMP/PKA signaling pathway.
精子活力对于男性生殖或自然受精至关重要。环磷酸腺苷（cAMP）/cAMP依赖性蛋白激酶A（PKA）信号通路通常被认为是调节哺乳动物精子活力的重要信号通路之一。由于哺乳动物脂肪组织中的锌-α2-糖蛋白（ZAG）活性是通过β(3)-肾上腺素能受体介导的，伴随着cAMP途径的上调，我们推测ZAG可能在精子活力调节中发挥同样的作用，即精子活力调节的一个新因子。因此，克隆了编码人ZAG的基因并制备了多克隆抗体，然后采用激光扫描共聚焦显微镜和流式细胞术在人精子中鉴定该蛋白。结果表明，ZAG蛋白主要定位于覆盖精子顶体、颈部和鞭毛中段的赤道前区域。此外，使用计算机辅助精子分析，我们发现抗人ZAG抗体在孵育90分钟或120分钟后可显著降低人上游精子的活力（分别为P<0.05和P<0.01），同时细胞内cAMP和PKA水平降低。总之，这些数据表明ZAG存在于人精子中，并可能通过cAMP/PKA信号通路参与精子活力的调节。
