Disease-associated mutations affect intracellular traffic and paracellular Mg2+ transport function of Claudin-16
Disease-associated mutations affect intracellular traffic and paracellular Mg2+ transport function of Claudin-16
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DOI：
10.1172/jci26323
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发表时间：
2006-04-01
影响因子：
15.9
通讯作者：
Hunziker, W
中科院分区：
文献类型：
--
作者：
Kausalya, PJ;Amasheh, S;Hunziker, W
紧密连接蛋白-16（Cldnl 6）选择性地在亨利氏袢的厚上升支的肾上皮细胞的紧密连接（Tjs）处表达，在那里它在二价阳离子的重吸收中起中心作用。在患有家族性低镁血症伴高钙尿症和肾钙质沉着症（FHHNC）的患者中已经鉴定出CLDN 16基因中的超过20种不同突变，所述FHHNC是一种过度肾Mg 2+和Ca 2+排泄的疾病。在这里，我们表明，致病突变可以导致Cldnl 6的细胞内滞留或影响其促进细胞旁Mg 2+转运的能力。我们表征的21个Cldnl 6突变体中的9个保留在内质网中，在那里它们经历蛋白酶体降解。三个突变体聚集在高尔基复合体中。两个突变体被有效地传递到溶酶体，一个通过网格蛋白介导的内吞作用后运输到细胞表面和其他不出现在质膜上。其余7个突变体定位于TJ，4个被发现在细胞旁Mg 2+转运缺陷。我们证明，药理学伴侣挽救了几个保留Cldn 16突变体的表面表达。我们的结论是，FHHNC可能是由Cldn 16突变引起的，该突变影响细胞内运输或细胞旁Mg 2+渗透性。与致病Cldn 16突变相关的分子缺陷的知识可能为治疗干预开辟新的途径。
Claudin-16 (Cldnl6) is selectively expressed at tight junctions (Tjs) of renal epithelial cells of the thick ascending limb of Henle's loop, where it plays a central role in the reabsorption of divalent cations. Over 20 different mutations in the CLDN16 gene have been identified in patients with familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), a disease of excessive renal Mg2+ and Ca2+ excretion. Here we show that disease-causing mutations can lead to the intracellular retention of Cldnl6 or affect its capacity to facilitate paracellular Mg2+ transport. Nine of the 21 Cldnl6 mutants we characterized were retained in the endoplasmic reticulum, where they underwent proteasomal degradation. Three mutants accumulated in the Golgi complex. Two mutants were efficiently delivered to lysosomes, one via clathrin-mediated endocytosis following transport to the cell surface and the other without appearing on the plasma membrane. The remaining 7 mutants localized to TJs, and 4 were found to be defective in paracellular Mg2+ transport. We demonstrate that pharmacological chaperones rescued surface expression of several retained Cldn16 mutants. We conclude that FHHNC can result from mutations in Cldn16 that affect intracellular trafficking or paracellular Mg2+ permeability. Knowledge of the molecular defects associated with disease-causing Cldn16 mutations may open new venues for therapeutic intervention.