Egg cortical granule N-acetylglucosaminidase is required for the mouse zona block to polyspermy.
Egg cortical granule N-acetylglucosaminidase is required for the mouse zona block to polyspermy.
复制标题
卵皮质颗粒N-乙酰葡萄糖氨基酶是小鼠Zona块至多性体经生的。
DOI：
10.1083/jcb.123.6.1431
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发表时间：
1993-12
影响因子：
7.8
通讯作者：
Shur, B D
中科院分区：
文献类型：
--
作者：
Miller, D J;Gong, X;Decker, G;Shur, B D
哺乳动物的卵子必须只与一个精子受精，以防止多倍体。在迄今为止所研究的大多数哺乳动物中，多精的主要障碍发生在透明带，即哺乳动物卵的外壳，在皮层颗粒的内容物分泌到卵泡周围间隙后。渗出液作用于带，使其失去与精子结合的能力，并被先前与带结合的精子穿透。然而，负责区阻断的皮质颗粒成分尚未确定。本文所述的研究表明，n -乙酰氨基葡萄糖酶定位于皮质颗粒中，并负责精子结合活性的丧失，导致多精带阻滞。受精前，精子最初通过精子表面的半乳糖酶和带糖蛋白ZP3的末端n -乙酰氨基氨基残基之间的相互作用与带结合（Miller， D. J.， M. B. Macek和B. D. Shur. 1992）。自然(Lond)。357:589 - 593)。受精后，这些galase结合位点在ZP3上丢失，这种效应可以通过n -乙酰氨基葡萄糖苷酶处理重复。因此，n -乙酰氨基葡萄糖酶或相关的糖苷酶可能存在于皮质颗粒中，并负责ZP3在受精时精子结合活性的丧失。在离子载体活化鸡蛋渗出液中测定的8种糖苷酶中，n -乙酰氨基葡萄糖酶的活性是其他酶的10倍。利用免疫电镜检测该酶定位于皮质颗粒。大约70%或90%的酶分别在离子载体激活或体内受精后从皮质颗粒中释放出来。在皮质颗粒中发现的N-乙酰氨基葡萄糖苷酶的同型异构体被鉴定为β -己糖氨基酶B，即β， β二聚体。用竞争性抑制剂或特异性抗体抑制活化卵子释放的N-乙酰氨基葡萄糖酶，导致多精子与透明带结合。另一种糖苷酶抑制剂或非免疫抗体对精子与活化卵子的结合没有影响。因此，卵子皮质颗粒n -乙酰氨基葡萄糖苷酶在受精时被释放，在那里它使精子的半乳糖酶结合位点失活，导致精子与透明带结合受阻。
The mammalian egg must be fertilized by only one sperm to prevent polyploidy. In most mammals studied to date, the primary block to polyspermy occurs at the zona pellucida, the mammalian egg coat, after exocytosis of the contents of the cortical granules into the perivitelline space. The exudate acts on the zona, causing it to lose its ability to bind sperm and to be penetrated by sperm previously bound to the zona. However, the cortical granule components responsible for the zona block have not been identified. Studies described herein demonstrate that N-acetylglucosaminidase is localized in cortical granules and is responsible for the loss in sperm-binding activity leading to the zona block to polyspermy. Before fertilization, sperm initially bind to the zona by an interaction between sperm surface GalTase and terminal N-acetylglucosamine residues on specific oligosaccharides of the zona glycoprotein ZP3 (Miller, D. J., M. B. Macek, and B. D. Shur. 1992. Nature (Lond.). 357:589-593). These GalTase-binding sites are lost from ZP3 after fertilization, an effect that can be duplicated by N-acetylglucosaminidase treatment. Therefore, N-acetylglucosaminidase, or a related glycosidase, may be present in cortical granules and be responsible for ZP3's loss of sperm-binding activity at fertilization. Of eight glycosidases assayed in exudates of ionophore-activated eggs, N-acetylglucosaminidase was 10-fold higher than any other activity. The enzyme was localized to cortical granules using immunoelectron microscopy. Approximately 70 or 90% of the enzyme was released from cortical granules after ionophore activation or in vivo fertilization, respectively. The isoform of N- acetylglucosaminidase found in cortical granules was identified as beta- hexosaminidase B, the beta, beta homodimer. Inhibition of N- acetylglucosaminidase released from activated eggs, with either competitive inhibitors or with specific antibodies, resulted in polyspermic binding to the zona pellucida. Another glycosidase inhibitor or nonimmune antibodies had no effect on sperm binding to activated eggs. Therefore, egg cortical granule N-acetylglucosaminidase is released at fertilization, where it inactivates the sperm GalTase- binding site, accounting for the block in sperm binding to the zona pellucida.