Bertocchio Jean-Philippe, Genetet Sandrine, Da Costa Lydie, Walsh Stephen B, Knebelmann Bertrand, Galimand Julie, Bessenay Lucie, Guitton Corinne, De Lafaille Renaud, Vargas-Poussou Rosa, Eladari Dominique, Mouro-Chanteloup Isabelle
Renal and Metabolic Diseases Unit, Assistance Publique-Hôpitaux de Paris, European Georges Pompidou Hospital, Paris, France.
Faculty of Medicine, Paris Descartes University, Paris, France.
Kidney Int Rep. 2020 Jan 13;5(3):348-357. doi: 10.1016/j.ekir.2019.12.020. eCollection 2020 Mar.
Anion exchanger 1 (AE1) ( gene product) is a membrane protein expressed in both kidney and red blood cells (RBCs): it exchanges extracellular bicarbonate (HCO ) for intracellular chloride (Cl) and participates in acid-base homeostasis. AE1 mutations in kidney α-intercalated cells can lead to distal renal tubular acidosis (dRTA). In RBC, AE1 (known as band 3) is also implicated in membrane stability: deletions can cause South Asian ovalocytosis (SAO).
We retrospectively collected clinical and biological data from patients harboring dRTA due to a mutation and analyzed HCO and Cl transports (by stopped-flow spectrophotometry) and expression (by flow cytometry, fluorescence activated cell sorting, and Coomassie blue staining) in RBCs, as well as RBC membrane stability (ektacytometry).
Fifteen patients were included. All experience nephrolithiasis and/or nephrocalcinosis, 2 had SAO and dRTA (dRTA SAO+), 13 dominant dRTA (dRTA SAO-). The latter did not exert specific RBC membrane anomalies. Both HCO and Cl transports were lower in patients with dRTA SAO+ than in those with dRTA SAO- or controls. Using 3 different extracellular probes, we report a decreased expression (by 52%, < 0.05) in dRTA SAO+ patients by fluorescence activated cell sorting, whereas total amount of protein was not affected.
Band 3 transport function and expression in RBCs from dRTA SAO- patients is normal. However, in SAO RBCs, impaired conformation of AE1/band 3 corresponds to an impaired function. Thus, the driver of acid-base defect during dominant dRTA is probably an impaired membrane expression.
阴离子交换蛋白1（AE1）（基因产物）是一种在肾脏和红细胞（RBC）中均有表达的膜蛋白：它将细胞外碳酸氢根（HCO₃⁻）与细胞内氯离子（Cl⁻）进行交换，并参与酸碱平衡。肾脏α - 闰细胞中的AE1突变可导致远端肾小管酸中毒（dRTA）。在红细胞中，AE1（也称为带3蛋白）也与膜稳定性有关：缺失可导致南亚椭圆形红细胞增多症（SAO）。
我们回顾性收集了因某突变导致dRTA患者的临床和生物学数据，并分析了红细胞中HCO₃⁻和Cl⁻的转运（通过停流分光光度法）、表达（通过流式细胞术、荧光激活细胞分选和考马斯亮蓝染色）以及红细胞膜稳定性（激光衍射法）。
纳入了15名患者。所有患者均有肾结石和/或肾钙质沉着症，2例患有SAO和dRTA（dRTA SAO⁺），13例为单纯性dRTA（dRTA SAO⁻）。后者未出现特定的红细胞膜异常。dRTA SAO⁺患者的HCO₃⁻和Cl⁻转运均低于dRTA SAO⁻患者或对照组。使用3种不同的细胞外探针，我们通过荧光激活细胞分选报告dRTA SAO⁺患者的表达降低（降低52%，P < 0.05），而蛋白质总量未受影响。
dRTA SAO⁻患者红细胞中的带3蛋白转运功能和表达正常。然而，在SAO红细胞中，AE1/带3蛋白的构象受损对应于功能受损。因此，单纯性dRTA期间酸碱缺陷的驱动因素可能是膜表达受损。
