Analysis of the process of localization of fertilin to the sperm posterior head plasma membrane domain during sperm maturation in the epididymis.
Analysis of the process of localization of fertilin to the sperm posterior head plasma membrane domain during sperm maturation in the epididymis.
复制标题
精子在附睾成熟过程中受精素定位于精子后头质膜域的过程分析。
DOI：
10.1006/dbio.1997.8700
复制
发表时间：
1997
影响因子：
2.7
通讯作者：
Myles,DG
中科院分区：
文献类型：
--
作者：
Hunnicutt,GR;Koppel,DE;Myles,DG
受精素是一种异源二聚体(α和β亚基)精子质膜蛋白。这两个亚基都属于ADAM蛋白家族的表面蛋白，含有去整合素和金属蛋白酶结构域。受精素通过受精素β去整合素域中的结合位点将精子与卵子质膜结合，从而发挥精卵融合的作用。在豚鼠睾丸精子中，受精素分布在整个精子头部的质膜上，但仅在精子穿过附睾后才出现在精子头部后部。如果用胰酶短暂处理睾丸精子，这种受精素到后头的重新分配可以部分模仿体外培养的睾丸精子。在这项研究中，我们使用免疫荧光和数字图像分析来分析受精素是如何限制在后脑的。我们发现，由于前头受精素分子迁移到后头区域，受精素变得局限于后头。对附睾七个区域的受精素免疫荧光模式和免疫印迹的比较表明，受精素开始迁移到后头和全长受精素β前体(85 kDa Pro-β形式)到75 kDa中间体Pro-β*的蛋白质分解过程之间存在时间相关性。迁移的完成与Pro-β*进一步切割成25-28 kDa的成熟形式相吻合。我们的数据表明，受精素Pro-β到Pro-β*的切割可能启动了受精素向后头部区域的迁移，并在定位到该膜结构域后，Pro-β*被切割成成熟的β。我们还报告了一种共同的机制可能被用来改变其他精子表面分子的定位模式的证据。其他表面蛋白定位于精子的后部或前部膜区，同时受精素定位于后部头部。这些对表面蛋白定位的限制也被证明在精子游泳和进行顶体反应的能力发展之前，因此在精子功能之前，表面蛋白的重新分布可能是必要的。
Fertilin is a heterodimeric (subunits α and β) sperm plasma membrane protein. Both subunits belong to the ADAM protein family of surface proteins that containa disintegrin anda metalloprotease domain. Fertilin functions in sperm–egg fusion by binding the sperm to the egg plasma membrane via a binding site in the disintegrin domain of fertilin β. On testicular sperm of guinea pig, fertilin is distributed on the plasma membrane over the entire sperm head, but is found only on the posterior head once sperm have passed through the epididymis. This redistribution of fertilin to the posterior head can be partially mimickedin vitroif testicular sperm are briefly treated with trypsin. In this study we used immunofluorescence and digital image analysis to analyze how fertilin becomes restricted to the posterior head. We found that fertilin became restricted to the posterior head by migration of anterior head fertilin molecules into the posterior head domain. Comparison of immunofluorescence patterns and immunoblots of fertilin from seven regions of the epididymis showed a temporal correlation between the beginning of fertilin's migration to the posterior head and the proteolytic processing of the full-length fertilin β precursor (the 85-kDa pro-β form) to a 75-kDa intermediate, pro-β*. Completion of the migration coincided with the further cleavage of pro-β* to the 25- to 28-kDa mature form. Our data suggest that the cleavage of fertilin pro-β to pro-β* may initiate fertilin's migration into the posterior head domain and, after localization to that membrane domain, pro-β* is cleaved to mature β. We also report evidence that a common mechanism may be used to change the localization pattern of other sperm surface molecules. Other surface proteins were shown to become localized to either the posterior or the anterior head membrane domains on sperm at the same time fertilin became localized to the posterior head. These restrictions of surface protein localizations were also shown to immediately precede the development of the sperm's ability to swim and undergo the acrosome reaction, and thus redistribution of surface proteins may be necessary before sperm become functional.