Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Hum Reprod. 2010 Jan;25(1):42-51. doi: 10.1093/humrep/dep359. Epub 2009 Oct 14.
Precise sperm-oocyte interaction is a critical event for successful fertilization. However, the identity of molecules involved in this process in humans remains largely unknown. This report describes the identification and characterization of a novel cell-surface protein and its potential role in human sperm-oocyte interaction.
We previously identified an orphan guanylyl cyclase receptor (mouse GC-G) highly enriched in mouse testis and involved in sperm activation. By using a comparative genomic approach, we found the homologue gene in human (hGC-G) composed of 21 exons, spanning a minimum of 48 kb on chromosome 10q25. Real-time RT-PCR analysis revealed hGC-G mRNA selectively expressed in testis but with low or no expression in all other tissues examined. Compared with mGC-G, the hGC-G transcript contains three 1-bp deletions and two in-frame termination codons, which results in a short putative receptor-like polypeptide. Western blot analysis with an anti-hGC-G-specific antibody confirmed the protein expression of hGC-G in human sperm lysate. Flow cytometry and confocal immunofluorescence analysis demonstrated the localization of hGC-G protein on the acrosome cap and equatorial segment of mature human sperm. In addition, an integrin-binding Arg-Gly-Asp (RGD) motif was found in the extracellular domain of hGC-G. Pre-incubation of the hGC-G RGD peptide with zona pellucida-free oocytes greatly decreased the binding of human sperm to hamster oocytes, which suggests a role for hGC-G role in sperm-oocyte interaction.
hGC-G is a novel surface protein on human sperm and potentially mediates sperm-oocyte interaction through its RGD-containing motif.
精确的精卵相互作用是受精成功的关键事件。然而，人类在这一过程中涉及的分子的身份在很大程度上仍然未知。本报告描述了一种新型细胞表面蛋白的鉴定和特征及其在人精卵相互作用中的潜在作用。
我们之前鉴定了一种在小鼠睾丸中高度富集的孤儿鸟苷酸环化酶受体（小鼠 GC-G），并参与精子激活。通过使用比较基因组学方法，我们在人类中发现了同源基因（hGC-G），由 21 个外显子组成，跨越染色体 10q25 的最小 48kb。实时 RT-PCR 分析显示 hGC-GmRNA 选择性地在睾丸中表达，但在所有检查的其他组织中表达水平低或无。与 mGC-G 相比，hGC-G 转录本包含三个 1bp 的缺失和两个框内终止密码子，导致短的假定受体样多肽。用抗 hGC-G 特异性抗体的 Western blot 分析证实了 hGC-G 蛋白在人精子裂解物中的表达。流式细胞术和共聚焦免疫荧光分析显示 hGC-G 蛋白定位于成熟人精子的顶体帽和赤道段。此外，在 hGC-G 的细胞外结构域中发现了一个整合素结合的 Arg-Gly-Asp（RGD）基序。hGC-GRGD 肽与透明带游离卵母细胞预孵育极大地减少了人精子与仓鼠卵母细胞的结合，这表明 hGC-G 在精卵相互作用中起作用。
hGC-G 是人类精子上的一种新型表面蛋白，通过其含有 RGD 的基序潜在地介导精卵相互作用。
