Tamm-Horsfall Glycoprotein Interacts with Renal Outer Medullary Potassium Channel ROMK2 and Regulates Its Function
Tamm-Horsfall Glycoprotein Interacts with Renal Outer Medullary Potassium Channel ROMK2 and Regulates Its Function
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DOI：
10.1074/jbc.m110.149880
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发表时间：
2011-01-21
影响因子：
4.8
通讯作者：
Waldegger, Siegfried
中科院分区：
文献类型：
--
作者：
Renigunta, Aparna;Renigunta, Vijay;Waldegger, Siegfried
Tamm-Horsfall糖蛋白（THGP）或尿调蛋白是一种仅沿着肾单位的粗升支（TAL）和早期远曲小管（DCT）表达的膜蛋白。THGP编码基因的突变导致家族性青少年高尿酸血症肾病（FJHN）、2型髓性囊性肾病（MCKD-2）和肾小球囊性肾病（GCKD）。THGP的理化和生物学性质已被广泛研究，但其在TAL中的生理功能仍不清楚。我们利用人肾脏cDNA文库进行酵母双杂交筛选，并确定THGP作为肾脏外髓钾通道（ROMK 2）的潜在相互作用伴侣，ROMK 2是盐重吸收过程中的关键参与者，沿着TAL。通过电生理技术对非洲爪蟾卵母细胞进行的功能分析显示，当与THGP共表达时，ROMK电流振幅大幅增加。THGP的作用对ROMK 2是特异性的，并且在与与ROMK相关的内向整流钾通道Kir2.x共表达时不影响电流幅度。单通道电导率和开放概率的ROMK 2没有改变THGP的共表达，而增加表面表达的ROMK 2，分别通过膜片钳分析和发光表面定量测定。尽管保留了与ROMK 2的相互作用，但引起疾病的THGP突变体未能增加其电流幅度和表面表达。与WT动物相比，THGP（-/-）小鼠在细胞内囊泡隔室中表现出增加的ROMK积累。因此，THGP对ROMK功能的调节赋予了THGP对肾离子转运的新作用，并可能有助于在FJHN/MCKD-2/GCKD患者中观察到的盐消耗。
Tamm-Horsfall glycoprotein (THGP) or Uromodulin is a membrane protein exclusively expressed along the thick ascending limb (TAL) and early distal convoluted tubule (DCT) of the nephron. Mutations in the THGP encoding gene result in Familial Juvenile Hyperuricemic Nephropathy (FJHN), Medullary Cystic Kidney Disease type 2 (MCKD-2), and Glomerulocystic Kidney Disease (GCKD). The physicochemical and biological properties of THGP have been studied extensively, but its physiological function in the TAL remains obscure. We performed yeast two-hybrid screening employing a human kidney cDNA library and identified THGP as a potential interaction partner of the renal outer medullary potassium channel (ROMK2), a key player in the process of salt reabsorption along the TAL. Functional analysis by electrophysiological techniques in Xenopus oocytes showed a strong increase in ROMK current amplitudes when co-expressed with THGP. The effect of THGP was specific for ROMK2 and did not influence current amplitudes upon co-expression with Kir2.x, inward rectifier potassium channels related to ROMK. Single channel conductance and open probability of ROMK2 were not altered by co-expression of THGP, which instead increased surface expression of ROMK2 as determined by patch clamp analysis and luminometric surface quantification, respectively. Despite preserved interaction with ROMK2, disease-causing THGP mutants failed to increase its current amplitude and surface expression. THGP(-/-) mice exhibited increased ROMK accumulation in intracellular vesicular compartments when compared with WT animals. Therefore, THGP modulation of ROMK function confers a new role of THGP on renal ion transport and may contribute to salt wasting observed in FJHN/MCKD-2/GCKD patients.