Université Pierre et Marie Curie, Université Paris Descartes, INSERM/UMRS 812, Centre National de la Recherche Scientifique ERL 7226, Laboratoire de génomique, physiologie et physiopathologie ŕenales, Center de Recherche des Cordeliers, 15 rue de I'Ecole de Medecine, Paris, France.
Biochem J. 2011 Feb 15;434(1):61-72. doi: 10.1042/BJ20101411.
Mutations in the anion exchanger pendrin are responsible for Pendred syndrome, an autosomal recessive disease characterized by deafness and goitre. Pendrin is highly expressed in kidney collecting ducts, where it acts as a chloride/bicarbonate exchanger and thereby contributes to the regulation of acid-base homoeostasis and blood pressure. The present study aimed to characterize the intrinsic properties of pendrin. Mouse pendrin was transfected in HEK (human embryonic kidney) 293 and OKP (opossum kidney proximal tubule) cells and its activity was determined by monitoring changes in the intracellular pH induced by variations of transmembrane anion gradients. Combining measurements of pendrin activity with mathematical modelling we found that its affinity for Cl-, HCO3- and OH- varies with intracellular pH, with increased activity at low intracellular pH. Maximal pendrin activity was also stimulated at low extracellular pH, suggesting the presence of both intracellular and extracellular proton regulatory sites. We identified five putative pendrin glycosylation sites, only two of which are used. Mutagenesis-induced disruption of pendrin glycosylation did not alter its cell-surface expression or polarized targeting to the apical membrane and basal activity, but fully abrogated its sensitivity to extracellular pH. The hither to unknown regulation of pendrin by external pH may constitute a key mechanism in controlling ionic exchanges across the collecting duct and inner ear.
阴离子交换蛋白 pendrin 的突变可导致 Pendred 综合征，这是一种常染色体隐性遗传病，其特征为耳聋和甲状腺肿。Pendrin 在肾脏集合管中高度表达，作为氯离子/碳酸氢根离子交换体，有助于调节酸碱平衡和血压。本研究旨在研究 pendrin 的内在特性。将小鼠 pendrin 转染到 HEK（人胚肾）293 和 OKP（负鼠肾近端小管）细胞中，并通过监测跨膜阴离子梯度变化引起的细胞内 pH 变化来确定其活性。结合 pendrin 活性的测量和数学建模，我们发现其对 Cl-、HCO3-和 OH-的亲和力随细胞内 pH 值而变化，在低细胞内 pH 值时活性增加。低细胞外 pH 值也可刺激最大 pendrin 活性，表明存在细胞内和细胞外质子调节位点。我们鉴定了 pendrin 的五个潜在糖基化位点，其中只有两个被使用。突变诱导的 pendrin 糖基化破坏不会改变其细胞表面表达或极性靶向到顶膜和基底活性，但完全消除了其对细胞外 pH 值的敏感性。pendrin 受到外部 pH 值的调节，这一至今未知的机制可能构成了控制集合管和内耳离子交换的关键机制。
