Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
J Cell Physiol. 2011 Nov;226(11):2740-6. doi: 10.1002/jcp.22854.
Voltage-sensitive phosphatases (VSPs) are unique proteins in which membrane potential controls enzyme activity. They are comprised of the voltage sensor domain of an ion channel coupled to a lipid phosphatase specific for phosphoinositides, and for ascidian and zebrafish VSPs, the phosphatase activity has been found to be activated by membrane depolarization. The physiological functions of these proteins are unknown, but their expression in testis and embryos suggests a role in fertilization or development. Here we investigate the expression pattern and voltage dependence of VSPs in two frog species, Xenopus laevis and Xenopus tropicalis, that are well suited for experimental studies of these possible functions. X. laevis has two VSP genes (Xl-VSP1 and Xl-VSP2), whereas X. tropicalis has only one gene (Xt-VSP). The highest expression of these genes was observed in testis, ovary, liver, and kidney. Our results show that while Xl-VSP2 activates only at positive membrane potentials outside of the physiological range, Xl-VSP1 and Xt-VSP phosphatase activity is regulated in the voltage range that regulates sperm-egg fusion at fertilization.
电压敏感磷酸酶（VSPs）是一类独特的蛋白，其活性受膜电位调控。它们由离子通道的电压感受器域与特定的磷酸肌醇脂质磷酸酶组成，已发现有孔虫和斑马鱼 VSP 的磷酸酶活性可被膜去极化激活。这些蛋白的生理功能尚不清楚，但它们在睾丸和胚胎中的表达提示其在受精或发育中可能具有作用。本文研究了两种适合这些可能功能的实验研究的蛙类，即非洲爪蟾（Xenopus laevis）和热带爪蟾（Xenopus tropicalis）中的 VSP 的表达模式和电压依赖性。非洲爪蟾有两个 VSP 基因（Xl-VSP1 和 Xl-VSP2），而热带爪蟾只有一个基因（Xt-VSP）。这些基因的表达丰度在睾丸、卵巢、肝脏和肾脏中最高。结果表明，Xl-VSP2 仅在正膜电位且超出生理范围时被激活，而 Xl-VSP1 和 Xt-VSP 的磷酸酶活性在受精时调节精子-卵子融合的电压范围内受到调控。
