Functional and developmental expression of a zebrafish Kir1.1 (ROMK) potassium channel homologue Kcnj1
Functional and developmental expression of a zebrafish Kir1.1 (ROMK) potassium channel homologue Kcnj1
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DOI：
10.1113/jphysiol.2010.200295
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发表时间：
2011-03-15
影响因子：
5.5
通讯作者：
White, Stanley J.
中科院分区：
文献类型：
--
作者：
Abbas, Leila;Hajihashemi, Saeed;White, Stanley J.
由于在进化过程中对发育途径和遗传物质的保护，斑马鱼胚胎等非哺乳动物“模式生物”正在成为探索人类疾病病因和潜在治疗方法的宝贵工具。离子通道是形成毛孔的蛋白质，通过允许离子流过生物膜来帮助建立和控制电梯度。人体每个器官的各种关键生理机制都依赖于离子通道的活性。在这篇文章中，我们证明了一个钾选择通道，它是人类肾脏盐重吸收和钾排泄的基础，也在斑马鱼的细胞中表达，而斑马鱼细胞是盐平衡的重要调节因素。斑马鱼中该通道的表达中断会对心脏活动产生影响，这与该通道在胚胎中控制钾平衡的作用是一致的。斑马鱼Danio rerio正在成为研究一些人类肾脏疾病的重要模式生物，但许多蛋白同源基因在斑马鱼肾单位中的表达部位和生理作用仍未确定。在这里，我们发现斑马鱼钾通道与哺乳动物肾脏钾通道ROMK同源。该基因(Kcnj1)编码一种蛋白(Kcnj1)，在非洲爪哇卵母细胞中表达时，表现出对pH和Ba2+敏感的K+选择电流，但与哺乳动物的通道不同，它对多肽抑制剂Tertiapin-Q完全不敏感。在原肾中，kcnj1转录本的表达局限于远端区域，并与氯化钠转运蛋白Nkcc、氯离子通道ClC-Ka和ClC-Ka/b辅助亚基Barttin的表达重叠，提示稀释片段的位置。在表面细胞的一个亚群中，kcnj1与Na+/K+-ATPase的a1a.4亚型共表达，表明这些细胞是该上皮中潜在的K+分泌细胞。在发育后期，kcnj1出现在发育中的鳃细胞中，该细胞也表达a1a.4亚单位。吗啡反义介导的kcnj1基因敲除伴随着一过性心动过速和随后的心动过缓，这种影响与胚胎细胞外K+浓度的变化一致。我们的发现表明，Kcnj1在与渗透调节相关的细胞中表达，并作为K+外流途径，在发育中的胚胎中维持细胞外K+水平。
Non-technical summaryDue to the conservation of developmental pathways and genetic material over the course of evolution, non-mammalian 'model organisms' such as the zebrafish embryo are emerging as valuable tools to explore causes and potential treatments for human diseases. Ion channels are proteins that form pores and help to establish and control electrical gradients by allowing the flow of ions across biological membranes. A diverse range of key physiological mechanisms in every organ in the body depends on the activity of ion channels. In this paper, we show that a potassium-selective channel that underlies salt reabsorption and potassium excretion in the human kidney is also expressed in zebrafish in cells that are important regulators of salt balance. Disruption of the channel's expression in zebrafish leads to effects on the activity of the heart, consistent with a role for this channel in the control of potassium balance in the embryo.The zebrafish, Danio rerio, is emerging as an important model organism for the pathophysiological study of some human kidney diseases, but the sites of expression and physiological roles of a number of protein orthologues in the zebrafish nephron remain mostly undefined. Here we show that a zebrafish potassium channel is orthologous to the mammalian kidney potassium channel, ROMK. The cDNA (kcnj1) encodes a protein (Kcnj1) that when expressed in Xenopus laevis oocytes displayed pH- and Ba2+-sensitive K+-selective currents, but unlike the mammalian channel, was completely insensitive to the peptide inhibitor tertiapin-Q. In the pronephros, kcnj1 transcript expression was restricted to a distal region and overlapped with that of sodium-chloride cotransporter Nkcc, chloride channel ClC-Ka, and ClC-Ka/b accessory subunit Barttin, indicating the location of the diluting segment. In a subpopulation of surface cells, kcnj1 was coexpressed with the a1a.4 isoform of the Na+/K+-ATPase, identifying these cells as potential K+ secretory cells in this epithelium. At later stages of development, kcnj1 appeared in cells of the developing gill that also expressed the a1a.4 subunit. Morpholino antisense-mediated knockdown of kcnj1 was accompanied by transient tachycardia followed by bradycardia, effects consistent with alterations in extracellular K+ concentration in the embryo. Our findings indicate that Kcnj1 is expressed in cells associated with osmoregulation and acts as a K+ efflux pathway that is important in maintaining extracellular levels of K+ in the developing embryo.