通过卵肽精子活化肽诱导的膜电位变化对海胆精子中电压敏感型钠氢交换的调节

Modulation of the voltage-sensitive Na+/H+ exchange in sea urchin spermatozoa through membrane potential changes induced by the egg peptide speract.

作者信息

Lee H C, Garbers D L

出版信息

J Biol Chem. 1986 Dec 5;261(34):16026-32.

Abstract

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.

摘要

海胆精子的运动能力可通过内部pH值的碱化来激活，先前的研究表明，内部pH值可由鞭毛质膜中存在的电压敏感型Na⁺/H⁺交换体调节。在本研究中，对从卵条件培养基中纯化的一种肽——精子活化肽（speract）对Na⁺/H⁺交换的影响进行了研究。所提供的证据表明，精子活化肽可激活鞭毛膜中的K⁺通道，并通过膜电位的相应变化来调节Na⁺/H⁺交换活性。在存在亲脂性离子四苯基鏻或高浓度外部Na⁺的情况下，分离出的鞭毛会发生去极化，并且Na⁺/H⁺交换体受到抑制。精子活化肽和缬氨霉素（一种K⁺离子载体）能够在任何一种去极化条件下重新激活²²Na⁺摄取、H⁺外流以及鞭毛内pH值的碱化。使用3,3'-二丙基硫代二碳菁碘化物进行的膜电位测量表明，精子活化肽或缬氨霉素均可使膜复极化。精子活化肽诱导的电压变化不需要Na⁺，但对[K⁺]敏感。因此，精子活化肽在含有10 mM K⁺的无Na⁺海水中会引起轻微去极化，但在含有2 mM K⁺的情况下会引起超极化。用K⁺电极测量发现，精子活化肽诱导的K⁺外流增加2 - 5倍，这进一步支持了鞭毛中K⁺通道的激活。通过电压测量评估，精子活化肽激活通道的离子选择性为K⁺＞Rb⁺＞Cs⁺。精子活化肽的半数有效浓度约为0.2 nM。通过对完整海胆精子使用精子活化肽或反应肽（resact）证实，肽诱导的H⁺和K⁺外流是由受体介导的，在同源精子中，这些肽仅能刺激K⁺外流并逆转四苯基鏻对H⁺外流的抑制作用。因此，卵肽对电压敏感型Na⁺/H⁺交换的调节似乎是间接的，并且是通过其对膜电位的作用来耦合的。