SPERM CHEMOTAXIS - EGG PEPTIDES CONTROL CYTOSOLIC CALCIUM TO REGULATE FLAGELLAR RESPONSES
SPERM CHEMOTAXIS - EGG PEPTIDES CONTROL CYTOSOLIC CALCIUM TO REGULATE FLAGELLAR RESPONSES
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DOI：
10.1006/dbio.1994.1229
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发表时间：
1994-09-01
影响因子：
2.7
通讯作者：
BABCOCK, DF
中科院分区：
文献类型：
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作者：
COOK, SP;BROKAW, CJ;BABCOCK, DF
零碎的证据表明细胞内[Ca2+] （Ca-i）介导精子趋化。然而，游泳反应与化学引诱剂诱导的Ca-i改变之间的相关性以及化学引诱剂梯度如何控制Ca-i的解释都不存在。在这里，Ca-i的增加是由卵磷脂产生的——以前不知道会引起鞭毛反应——通过3-异丁基-1-甲基黄嘌呤（IBMX）治疗而延长的。鞭毛波形的不对称性增加了40%，游泳路径变成了紧密的圆形。此外，这两种反应都需要外部Ca2+（精子对卵子和蛋制品的趋化性也是如此）。Ca-i通过已建立的趋化肽反应增加，也需要外部Ca2+， IBMX增强。因此，不同的鸡蛋肽可能使用基本相似的机制来控制ca - 1，从而在趋化性中游动行为。精子不断增加的添加量产生了适应性膜电位和Ca-i反应，表明精子可以在较宽的浓度范围内检测到卵肽的增加梯度。我们提供了一个模型，在这个模型中，浅的或递减的梯度会提高Ca-i并改变游泳路径，但足够陡的梯度会使Ca-i保持低水平并线性游泳，直到到达卵。一个负反馈回路，由cgmp介导的精子K+通道激活启动，并由随后的胍基环化酶失活终止，可能协调梯度检测与ca - 1的控制。通过急剧增加的卵磷脂梯度持续刺激更多的受体，从而维持膜超极化，抑制Ca2+进入和Ca-i升高。因此，趋化性的分子基础被解释为肽浓度的空间梯度在时域上转化为K+通道活性的变化。(C) 1994学术出版社，Inc.
Fragmentary evidence indicates that intracellular [Ca2+] (Ca-i) mediates sperm chemotaxis. However, neither correlations of swimming responses to chemoattractant-induced alterations of Ca-i nor explanations of how chemoattractant gradients control Ca-i exist. Here Ca-i increases produced by the egg peptide speract-not previously known to cause flagellar responses-were prolonged by treatment with 3-isobultyl-1-methylxanthine (IBMX). Flagellar waveform asymmetry then increased 40% and swimming paths became tightly circular. Moreover, both responses required external Ca2+ (as does sperm chemotaxis to eggs and egg products). Ca-i increases by the established chemotactic peptide resact also required external Ca2+ and were enhanced by IBMX. Therefore, diverse egg peptides may use fundamentally similar mechanisms to control Ca-i and thereby swimming behavior in chemotaxis. Repetitive increasing additions of speract produced adaptive membrane potential and Ca-i responses indicating that sperm can detect increasing gradients of egg peptide over a broad concentration range. We offer a model in which shallow or decreasing gradients elevate Ca-i and redirect swimming paths but sufficiently steep gradients keep Ca-i low and swimming linear until the egg is reached. A negative-feedback loop, initiated by cGMP-mediated activation of sperm K+ channels and terminated by subsequent inactivation of guanylyl cyclase, may coordinate gradient detection with control of Ca-i. Continued stimulation of more receptors by steeply increasing gradients of egg peptide thus maintains membrane hyperpolarization and suppresses Ca2+ entry and Ca-i elevation. The molecular basis for chemotaxis therefore is explained as translation of the spatial gradient of peptide concentration into changes in K+ channel activity in the time domain. (C) 1994 Academic Press, Inc.