Mutations in an unrecognized internal NPT2A PDZ motif disrupt phosphate transport and cause congenital hypophosphatemia.
Mutations in an unrecognized internal NPT2A PDZ motif disrupt phosphate transport and cause congenital hypophosphatemia.
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DOI：
10.1042/bcj20230020
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发表时间：
2023-05-17
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钠离子依赖的磷酸协同转运体-2A(NPT2A，SLC34A1)是细胞外磷稳态的主要调节因子。它最突出的结构元件是一个羧基末端的PDZ配体，它与Na+/H+交换调节因子-1(NHERF1，SLC9A3R1)结合。NHERF1是一个多结构域的PDZ蛋白，它建立了NPT2A膜的定位，是激素抑制的磷酸盐运输所必需的。NPT2a还具有一个未鉴定的内部PDZ配体。最近的两份临床报告描述了在PDZ内部基序中含有Arg495His或Arg495Cys变异的儿童先天性低磷血症。野生型内部494TRL496PDZ配体与NHERF1 PDZ2结合，我们认为这是一个调节结构域。用494AAA496替换去除PDZ内部配体可阻止激素抑制的磷酸盐转运。互补的方法，包括CRISPR/Cas9技术、定点突变、共聚焦显微镜和建模，表明NPT2AArg495His或Arg495Cys变体不支持PTH或FGF23对磷酸盐运输的作用。免疫共沉淀实验表明，这两个变体与NHERF1结合的方式与WT NPT2A相似。然而，与WT NPT2A相比，NPT2A Arg495His或Arg495Cys变体保留在顶膜，不内化对PTH的反应。我们预测Cys或他对带电的Arg495的取代改变了静电，阻止了上游Thr494的磷酸化，干扰了激素作用下的磷酸盐吸收，并抑制了NPT2A的运输。我们提出了一个模型，其中羧基末端的PDZ配体定义了顶端定位NPT2A，而内部的PDZ配体对于激素触发的磷酸盐运输是必不可少的。
The Na+-dependent phosphate cotransporter-2A (NPT2A, SLC34A1) is a primary regulator of extracellular phosphate homeostasis. Its most prominent structural element is a carboxy-terminal PDZ ligand that binds Na+/H+ Exchanger Regulatory Factor-1 (NHERF1, SLC9A3R1). NHERF1, a multidomain PDZ protein, establishes NPT2A membrane localization and is required for hormone-inhibitable phosphate transport. NPT2A also possesses an uncharacterized internal PDZ ligand. Two recent clinical reports describe congenital hypophosphatemia in children harboring Arg495His or Arg495Cys variants within the internal PDZ motif. The wild-type internal 494TRL496 PDZ ligand binds NHERF1 PDZ2, which we consider a regulatory domain. Ablating the internal PDZ ligand with a 494AAA496 substitution blocked hormone-inhibitable phosphate transport. Complementary approaches, including CRISPR/Cas9 technology, site-directed mutagenesis, confocal microscopy, and modeling, showed that NPT2A Arg495His or Arg495Cys variants do not support PTH or FGF23 action on phosphate transport. Coimmunoprecipitation experiments indicate that both variants bind NHERF1 similarly to WT NPT2A. However, in contrast with WT NPT2A, NPT2A Arg495His, or Arg495Cys variants remain at the apical membrane and are not internalized in response to PTH. We predict that Cys or His substitution of the charged Arg495 changes the electrostatics, preventing phosphorylation of the upstream Thr494, interfering with phosphate uptake in response to hormone action, and inhibiting NPT2A trafficking. We advance a model wherein the carboxy-terminal PDZ ligand defines apical localization NPT2A, while the internal PDZ ligand is essential for hormone-triggered phosphate transport.
影响因子：
3.7
作者：
Mamonova T;Zhang Q;Khajeh JA;Bu Z;Bisello A;Friedman PA
通讯作者：
Friedman PA