Cowan A E, Primakoff P, Myles D G
J Cell Biol. 1986 Oct;103(4):1289-97. doi: 10.1083/jcb.103.4.1289.
Evidence has been presented that the PH-20 protein functions in sperm adhesion to the egg zona pellucida (Primakoff, P., H. Hyatt, and D. G. Myles, 1985, J. Cell Biol., 101:2239-2244). The PH-20 protein migrates from its original surface domain to a new surface domain after the acrosome reaction (Myles, D. G., and P. Primakoff, 1984, J. Cell Biol., 99:1634-1641). The acrosome reaction is an exocytotic event that results in insertion of a region of the secretory granule membrane, the inner acrosomal membrane (IAM), into the plasma membrane. After the acrosome reaction, PH-20 protein migrates to the IAM from its initial domain on the posterior head surface. We have now found a new dynamic feature of the regulation of PH-20 protein on the sperm surface; exocytosis increases the surface expression of PH-20 protein. After the acrosome reaction there is an approximately threefold increase in the number of PH-20 antigenic sites on the sperm surface. These new antigenic sites are revealed on the surface by insertion of the IAM into the plasma membrane. Our evidence indicates that before the acrosome reaction an intracellular population of PH-20 antigen is localized to the IAM. When migration of the surface population of the PH-20 protein is prevented, PH-20 protein can still be detected on the IAM of acrosome-reacted sperm. Also, PH-20 protein can be detected on the IAM of permeabilized acrosome-intact sperm by indirect immunofluorescence. Thus, the sperm cell regulates the amount of PH-20 protein on its surface by sequestering about two-thirds of the protein on an intracellular membrane and subsequently exposing this population on the cell surface by an exocytotic event. This may be a general mechanism for regulating cell surface composition where a rapid increase in the amount of a cell surface protein is required.
已有证据表明，PH - 20蛋白在精子黏附于卵子透明带的过程中发挥作用（普里马科夫，P.，H. 海亚特，以及D. G. 迈尔斯，1985年，《细胞生物学杂志》，101:2239 - 2244）。顶体反应后，PH - 20蛋白从其原来的表面区域迁移至新的表面区域（迈尔斯，D. G.，以及P. 普里马科夫，1984年，《细胞生物学杂志》，99:1634 - 1641）。顶体反应是一种胞吐事件，导致分泌颗粒膜的一个区域，即顶体内膜（IAM）插入质膜。顶体反应后，PH - 20蛋白从其在后头部表面的初始区域迁移至IAM。我们现在发现了精子表面PH - 20蛋白调控的一个新的动态特征；胞吐作用增加了PH - 20蛋白的表面表达。顶体反应后，精子表面PH - 20抗原位点的数量增加了约三倍。这些新的抗原位点通过IAM插入质膜而在表面显现出来。我们的证据表明，在顶体反应之前，细胞内的PH - 20抗原群体定位于IAM。当阻止PH - 20蛋白表面群体的迁移时，在顶体反应后的精子的IAM上仍可检测到PH - 20蛋白。此外，通过间接免疫荧光法可在通透的顶体完整精子的IAM上检测到PH - 20蛋白。因此，精子细胞通过将约三分之二的蛋白隔离在细胞内膜上，随后通过胞吐事件将这部分蛋白群体暴露在细胞表面，来调节其表面PH - 20蛋白的量。这可能是一种调节细胞表面组成的普遍机制，在此机制中，需要细胞表面蛋白的量快速增加。
