Na^+/HCO_3-共转运体NBCe1的生理及病理学作用

Physiology and pathophysiology of Na^+/HCO_3- cotransporter NBCe1

维持机体的酸碱稳态对各项生理活动的有序进行具有根本性的意义,酸碱紊乱会导致一系列疾病。碳酸氢根(HCO3-)是机体中最重要的酸碱缓冲离子。SLC4家族的HCO3-跨膜转运体是机体最主要的HCO3-跨膜运输载体之一,在细胞的pH调控以及上皮细胞中HCO3-的吸收或分泌过程中起着非常重要的作用。SLC4家族的NBCe1(SLC4A4)是一个生电型的Na+/HCO3-共转运体,在各种组织中有着非常广泛的表达,具有极其重要的生理学作用。在肾脏近端肾小管中,NBCe1负责80%以上的HCO3-的重吸收,对于维持机体全局的酸碱平衡极其重要。人类的SLC4A4突变常导致严重的近端肾小管性酸中毒,且常伴有侏儒症、偏头疼、白内障、青光眼以及牙齿釉质发育异常等。本文对最近十多年来有关NBCe1的结构-功能关系、功能调控机制、NBCe1的生理及病理学作用机理等方面的研究进展进行综述与分析。

Na＋/HCO3- cotransporter NBCe1 is an electrogenic member of the solute carrier 4 （SLC4） family and plays important roles in intracellular pH regulation as well as transepithelial HCO3- movement. The physiological and pathological significance of NBCe1 has been well established by genetic studies with humans as well as knock-out study with mouse. NBCe1 is expressed in diverse tissues in mammals. The transporter plays an essential role in the maintenance of acid-base homeostasis in our body, being responsible for more ～80% of HCO3- reabsorption in the proximal renal tubule. In humans, a number of SLC4A4 mutations have been associated with proximal renal tubule acidosis that is often accompanied with short stature, ocular abnormalities （including cataract, glaucoma, and band keratopathy）, migraine, and/or defects in dental enamel development. In the present article, we review the molecular physiology, the structure/function relationship, the mechanisms underlying the functional regulation of NBCe1, as well as the physiological and pathological roles of the transporter.