Modulation of the voltage-sensitive Na+/H+ exchange in sea urchin spermatozoa through membrane potential changes induced by the egg peptide speract.
Modulation of the voltage-sensitive Na+/H+ exchange in sea urchin spermatozoa through membrane potential changes induced by the egg peptide speract.
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DOI：
10.1016/s0021-9258(18)66670-0
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发表时间：
1986-12
期刊：
影响因子：
--
通讯作者：
H. C. Lee;D. Garbers
中科院分区：
文献类型：
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作者：
H. C. Lee;D. Garbers
海胆精子活力可以激活碱化的内部pH值，和以前的研究表明，内部pH值可以调节电压敏感的Na+/H+交换存在于鞭毛质膜。本文研究了从鸡蛋条件培养液中提取的多肽speract对Na+/H+交换的影响。有证据表明，精子激活鞭毛膜上的K+通道，并通过膜电位的变化调节Na+/H+交换活性。在亲脂性离子四苯基磷或高外部Na+存在下，分离的鞭毛被去极化，Na+/H+交换被抑制。Speract和valinomycin，K+离子载体，能够重新激活22 Na+的吸收，H+流出，和碱化的鞭毛内pH值下的去极化条件。用碘化3，3 '-二丙基硫代二碳氰化物测定膜电位表明，无论是speract或缬氨霉素复极化。精子引起的电压变化不需要Na+，但对[K+]敏感。因此，speract在无Na+海水中诱导轻微的去极化与10 mM K+，但超极化与2 mM K+。用K+电极测定精子对K+外排的2-5倍刺激，进一步支持了鞭毛中K+通道的激活。通过电压测量评估的精子激活通道的离子选择性是K+大于Rb+大于Cs+。speract的半最大有效浓度约为0.2 nM。通过对完整的海胆精子使用speract或resact，证实了响应于肽的H+和K+流出是受体介导的，其中发现肽刺激K+流出，并且仅在同源精子中逆转四苯基鏻对H+流出的抑制。因此，鸡蛋肽对电压敏感性Na+/H+交换的调节似乎是间接的，并且通过其对膜电位的作用而偶联。
Sea urchin sperm motility can be activated by alkalinization of the internal pH, and previous studies have shown that the internal pH can be regulated by a voltage-sensitive Na+/H+ exchanger present in the flagellar plasma membrane. In this study, the effects of speract, a peptide purified from egg conditioned media, on the Na+/H+ exchange were investigated. Evidence presented indicates that speract activates K+ channels in the flagellar membrane and modulates the Na+/H+ exchange activity through resultant changes in membrane potential. In the presence of tetraphenylphosphonium, a lipophilic ion, or high external Na+, the isolated flagella were depolarized, and Na+/H+ exchanger was inhibited. Speract and valinomycin, a K+ ionophore, were able to reactivate 22Na+ uptake, H+ efflux, and alkalinization of intraflagellar pH under either of the depolarizing conditions. Membrane potential measurements using 3,3'-dipropylthiodicarbocyanide iodide indicated repolarization by either speract or valinomycin. The speract-induced voltage changes did not require Na+ but were sensitive to [K+]. Thus, speract induced a slight depolarization in Na+-free seawater with 10 mM K+ but a hyperpolarization with 2 mM K+. Further support for the activation of K+ channels in the flagella was the 2-5-fold stimulation of K+ efflux induced by speract as measured with a K+ electrode. The ionic selectivity of the speract-activated channel assessed by voltage measurements was K+ greater than Rb+ greater than Cs+. The half-maximally effective concentration of speract was about 0.2 nM. That the H+ and K+ efflux in response to peptide was receptor-mediated was confirmed by the use of speract or resact on intact sea urchin spermatozoa, where the peptides were found to stimulate K+ efflux and to reverse the tetraphenylphosphonium inhibition on H+ efflux only in the homologous spermatozoa. Modulation of the voltage-sensitive Na+/H+ exchange by egg peptides, therefore, appears to be indirect and is coupled through its action on membrane potential.