ACTIVATION OF VOLTAGE-DEPENDENT CALCIUM CHANNELS OF MAMMALIAN SPERM IS REQUIRED FOR ZONA-PELLUCIDA-INDUCED ACROSOMAL EXOCYTOSIS
ACTIVATION OF VOLTAGE-DEPENDENT CALCIUM CHANNELS OF MAMMALIAN SPERM IS REQUIRED FOR ZONA-PELLUCIDA-INDUCED ACROSOMAL EXOCYTOSIS
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DOI：
10.1016/0012-1606(92)90137-6
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发表时间：
1992-08-01
影响因子：
2.7
通讯作者：
BABCOCK, DF
中科院分区：
文献类型：
--
作者：
FLORMAN, HM;CORRON, ME;BABCOCK, DF
先前的工作表明，L型电压依赖性Ca 2+通道（VDCC）的拮抗剂阻止了哺乳动物精子中Cai的增加，这是通过在碱性K+培养基中孵育来促进的。在这里，我们提供了额外的证据，精子拥有VDCC，并表明其激活所需的Ca 2+进入介导的顶体胞吐在存在和不存在的卵子激动剂。具体而言，我们报告：（1）精子膜电位变化、Cai升高和顶体胞吐具有相似的K+剂量依赖性，与精子VDCC激活的大去极化的特征要求一致;（2）高亲和力结合位点VDCC拮抗剂PN 200 -110的Kd分别为0.35 ± 0.03和0.45 ± 0.06 nM; Bmax分别为16.0 ± 1.4和5.8 ± 0.8 fmole/mg蛋白质;（3）PN 200 -110和其他VDCC拮抗剂尼群地平、尼索地平、维拉帕米、地尔硫卓、Ni 2+或Co 2+抑制（IC 50分别为0.1、0.4、0.6、0.8、1.0、60和110 μM）由pH 0升高和膜去极化联合产生的顶体胞吐作用;（4）哺乳动物卵的ZP 3激动剂诱导的胞吐作用也被VDCC拮抗剂抑制，具有类似的剂量依赖性;（5）可能激活精子VDCC的去极化处理绕过了百日咳毒素对ZP 3诱导的胞吐作用的阻断。这些结果表明精子VDCC的激活足以诱导精子顶体胞吐，并且VDCC激活在ZP 3信号转导途径中是必需的。它们还表明，百日咳毒素的假定G蛋白靶点可能产生假定精子VDCC的必需但间接的激活。可能的干预事件包括VDCC的电压敏感性改变、膜去极化或两者。我们认为，去极化诱导的顶体反应可能提供了一个有用的系统，以调查随后的事件中的胞吐过程。
Previous work indicates that antagonists of the L-type voltage-dependent Ca2+channel (VDCC) prevent the Caiincrease in mammalian sperm that is promoted by incubation in alkaline, K+-based media. Here, we provide additional evidence that sperm possess VDCC and show that their activation is required for the Ca2+entry that mediates acrosomal exocytosis in both the presence and the absence of egg agonists. Specifically, we report that: (1) Sperm membrane potential changes, Caielevation, and acrosomal exocytosis have similar K+dose dependencies, consistent with a characteristic requirement of a large depolarization for activation of the sperm VDCC; (2) High affinity binding sites (Kd∼0.35 ± 0.03 and 0.45 ± 0.06 nM; Bmax= 16.0 ± 1.4 and 5.8 ± 0.8 fmole/mg protein) for the VDCC antagonist, PN200-110, respectively, are present in membrane preparations from sperm of the ram and bull; (3) PN200-110 and the other VDCC antagonists nitrendipine, nisoldipine, verapamil, diltiazem, Ni2+, or Co2+inhibit (IC50= 0.1, 0.4, 0.6, 0.8, 1.0, 60, and 110 μM, respectively) the acrosomal exocytosis produced by combined elevation of pH0and membrane depolarization; (4) Exocytosis induced by the ZP3 agonist of the mammalian egg also is inhibited by VDCC antagonists with similar dose dependencies; (5) Depolarizing treatments that presumably activate the sperm VDCC bypass the blockade of ZP3-induced exocytosis imposed by pertussis toxin. These results indicate that activation of the sperm VDCC is sufficient to induce sperm acrosomal exocytosis and that VDCC activation is necessary in the ZP3 signal transduction pathway. They also indicate that the presumed G-protein targets of pertussis toxin probably produce a required but indirect activation of the putative sperm VDCC. Possible intervening events include alteration of the voltage sensitivity of the VDCC, membrane depolarization, or both. We suggest that the depolarization-induced acrosome reaction may provide a useful system to investigate subsequent events in the exocytotic process.