Single amino acids in the carboxyl terminal domain of aquaporin-1 contribute to cGMP-dependent ion channel activation.
Single amino acids in the carboxyl terminal domain of aquaporin-1 contribute to cGMP-dependent ion channel activation.
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DOI：
10.1186/1472-6793-3-12
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发表时间：
2003-10-15
期刊：
影响因子：
--
通讯作者：
Yool AJ
中科院分区：
文献类型：
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作者：
Boassa D;Yool AJ
水通道蛋白-1（AQP 1）作为渗透性水通道和门控阳离子通道发挥功能。基于与环核苷酸门控通道和cGMP选择性磷酸二酯酶的氨基酸序列比对，假设细胞内cGMP激活AQP 1离子电导涉及羧基（C-）末端。电压钳分析人类AQP 1通道表达爪蟾卵母细胞表明，一氧化氮供体，硝普钠（SNP; 3-14 mM）激活的离子电导反应的剂量依赖性方式。阻断可溶性鸟苷酸环化酶阻止了反应。酶免疫测定证实了SNP和所得细胞内cGMP水平之间的线性剂量依赖性关系（在14 mM SNP下高达1700 fmol cGMP /卵母细胞）。这里的结果是第一次显示，离子通道激活的功效降低了AQP 1的突变在保守残基的C-末端结构域（天冬氨酸D237和赖氨酸K243）。这些数据支持的想法，有限的氨基酸序列之间的相似性发现三个不同类别的cGMP结合蛋白是重要的AQP 1作为cGMP门控离子通道的功能，并提供直接证据的AQP 1的C-末端结构域参与cGMP介导的离子通道激活。
Aquaporin-1 (AQP1) functions as an osmotic water channel and a gated cation channel. Activation of the AQP1 ion conductance by intracellular cGMP was hypothesized to involve the carboxyl (C-) terminus, based on amino acid sequence alignments with cyclic-nucleotide-gated channels and cGMP-selective phosphodiesterases. Voltage clamp analyses of human AQP1 channels expressed in Xenopus oocytes demonstrated that the nitric oxide donor, sodium nitroprusside (SNP; 3–14 mM) activated the ionic conductance response in a dose-dependent manner. Block of soluble guanylate cyclase prevented the response. Enzyme immunoassays confirmed a linear dose-dependent relationship between SNP and the resulting intracellular cGMP levels (up to 1700 fmol cGMP /oocyte at 14 mM SNP). Results here are the first to show that the efficacy of ion channel activation is decreased by mutations of AQP1 at conserved residues in the C-terminal domain (aspartate D237 and lysine K243). These data support the idea that the limited amino acid sequence similarities found between three diverse classes of cGMP-binding proteins are significant to the function of AQP1 as a cGMP-gated ion channel, and provide direct evidence for the involvement of the AQP1 C-terminal domain in cGMP-mediated ion channel activation.