Analysis of mouse fertilin in wild-type and fertilin β-/- sperm:: Evidence for C-terminal modification, α/β dimerization, and lack of essential role of fertilin α in sperm-egg fusion
Analysis of mouse fertilin in wild-type and fertilin β-/- sperm:: Evidence for C-terminal modification, α/β dimerization, and lack of essential role of fertilin α in sperm-egg fusion
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DOI：
10.1006/dbio.2000.9703
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发表时间：
2000-06-15
影响因子：
2.7
通讯作者：
Myles, DG
中科院分区：
文献类型：
--
作者：
Cho, CH;Ge, HY;Myles, DG
精子表面蛋白受精素在精子-卵子相互作用中发挥作用。在豚鼠和牛的精子上，受精素是α和β亚基的异源二聚体。这两个亚基最初都是作为前体合成的，然后通过去除N-末端结构域进行蛋白质水解性处理。由于小鼠是目前研究受精的主要哺乳动物物种，在本报告中，我们分析了小鼠受精素的结构、加工和表达。我们发现，小鼠受精素β的加工发生在附睾成熟过程中，涉及到细胞质尾部结构域和N-末端结构域的变化。尽管我们(R.袁等人，1997，J.Cell Biol.137,105-112)和其他人(M.S.Chen等，1999，J.Cell Biol.144,549-561)以前报道过成熟的受精素β为55-57 kDa，这里我们表明55 kDa是精子提取液中的一个无关蛋白质，它与识别前体但不识别成熟的受精素β的抗体发生交叉反应。比较野生型和受精素β基因敲除的精子的蛋白质印迹显示，真正的成熟的受精素β为45 kDa。我们还获得了小鼠受精素α和β以异源二聚体形式存在的直接证据。此外，我们发现，在缺乏受精素β亚基的小鼠中，成熟精子中不存在受精素α。一个被广泛提出的精子-卵子融合模型表明，受精素α是一种精子成分，它通过发生构象变化来促进膜融合，从而暴露出一种类似病毒的疏水融合肽。由于缺乏受精素α和受精素β的精子与卵子的融合率是野生型的50%，这一模型受到了质疑。相反，结果表明，其他配子表面分子促进了膜融合，而受精素在配子融合中的作用是在精子-卵子的质膜粘连中。(C)2000年学术出版社。
The sperm surface protein fertilin functions in sperm-egg interaction. On guinea pig and bovine sperm, fertilin is a heterodimer of alpha and beta subunits. Both subunits are initially synthesized as precursors and then proteolytically processed by removing N-terminal domains. Since the mouse is currently the main mammalian species in which fertilization is studied, in the present report, we analyzed the structure, processing, and expression of fertilin in mouse. We found that the processing of mouse fertilin beta occurs during epididymal maturation and involves changes in the cytoplasmic tail domain as well as the N-terminal domains. Although we (R. Yuan et al., 1997, J. Cell Biol. 137, 105-112) and others (M. S. Chen et al., 1999, J. Cell Biol. 144, 549-561) have previously reported that mature fertilin beta is 55-57 kDa, here we show that 55 kDa is an unrelated protein in the sperm extract which cross-reacts with an antibody that recognizes precursor, but not mature, fertilin beta. Comparison of Western blots of wild-type and fertilin beta knockout sperm revealed that authentic, mature fertilin beta is 45 kDa. We also obtained direct evidence that mouse fertilin alpha and beta exist as a heterodimer. In addition, we found that in mice lacking the fertilin beta subunit, fertilin alpha is absent from mature sperm. A widely proposed model for sperm-egg fusion suggests that fertilin alpha is the sperm component that promotes membrane fusion by undergoing a conformational change that exposes a virus-like, hydrophobic fusion peptide. Because sperm lacking fertilin alpha and fertilin beta can fuse with eggs at 50% the wild-type rate, this model is called into question. The results suggest instead that other gamete surface molecules act to promote membrane fusion and that fertilin's role in gamete fusion is in sperm-egg plasma membrane adhesion. (C) 2000 Academic Press.