Complexin I is required for mammalian sperm acrosomal exocytosis.
Complexin I is required for mammalian sperm acrosomal exocytosis.
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DOI：
10.1016/j.ydbio.2007.07.009
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发表时间：
2007-09
影响因子：
2.7
通讯作者：
Longmei Zhao;H. Burkin;Xudong Shi;Lingjun Li;K. Reim;David J. Miller
中科院分区：
文献类型：
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作者：
Longmei Zhao;H. Burkin;Xudong Shi;Lingjun Li;K. Reim;David J. Miller
许多细胞中调节的胞吐作用由SNARE复合体控制，其核心包括三种促进膜融合的蛋白质。复合蛋白I和II是高度相关的胞浆蛋白，与组装的SNARE复合体紧密结合，调节神经元的胞吐。像体细胞一样，精子经历调节的胞吐作用；然而，精子释放单个大的囊泡，顶体，其释放具有与神经元胞吐不同的特征。精子与哺乳动物卵细胞外基质(透明带)黏附后，顶体释放被触发，以允许卵衣穿透。膜融合发生在顶体内的多个点，但融合是如何被激活的，融合点的形成和进展是同步的，目前还不清楚。我们发现，在顶体完整的成熟精子中发现了复合体I和II，它们与SNAR复杂蛋白结合，在顶体胞吐(顶体反应)后的精子中没有检测到。尽管复合素I缺乏的精子顶体对钙离子载体有反应，但它们对卵子透明带蛋白没有顶体反应，在体外受精能力降低。复合蛋白II存在于复合蛋白I缺陷的精子中，其表达在复合蛋白I缺陷的睾丸中增加。因此，复合素I在两个相关但在形态上不同的分泌过程中发挥胞吐作用。精子是不同寻常的，因为它们同时表达复合蛋白I和复合蛋白II，但对复合蛋白I有独特和特定的要求。
Regulated exocytosis in many cells is controlled by the SNARE complex, whose core includes three proteins that promote membrane fusion. Complexins I and II are highly related cytosolic proteins that bind tightly to the assembled SNARE complex and regulate neuronal exocytosis. Like somatic cells, sperm undergo regulated exocytosis; however, sperm release a single large vesicle, the acrosome, whose release has different characteristics than neuronal exocytosis. Acrosomal release is triggered upon sperm adhesion to the mammalian egg extracellular matrix (zona pellucida) to allow penetration of the egg coat. Membrane fusion occurs at multiple points within the acrosome but how fusion is activated and the formation and progression of fusion points is synchronized is unclear. We show that complexins I and II are found in acrosome-intact mature sperm, bind to SNARE complex proteins, and are not detected in sperm after acrosomal exocytosis (acrosome reaction). Although complexin-I-deficient sperm acrosome-react in response to calcium ionophore, they do not acrosome-react in response to egg zona pellucida proteins and have reduced fertilizing ability, in vitro. Complexin II is present in the complexin-I-deficient sperm and its expression is increased in complexin-I-deficient testes. Therefore, complexin I functions in exocytosis in two related but morphologically distinct secretory processes. Sperm are unusual because they express both complexins I and II but have a unique and specific requirement for complexin I.