Jouret François, Auzanneau Céline, Debaix Huguette, Wada Ge-Hong Sun, Pretto Chrystel, Marbaix Etienne, Karet Fiona E, Courtoy Pierre J, Devuyst Olivier
Division of Nephrology, Université catholique de Louvain, 10 Avenue Hippocrate, Brussels, Belgium B-1200.
J Am Soc Nephrol. 2005 Nov;16(11):3235-46. doi: 10.1681/ASN.2004110935. Epub 2005 Sep 21.
The vacuolar H(+)-ATPase (V-ATPase) is a ubiquitous multisubunit pump that is responsible for acidification of intracellular organelles. In the kidney, a particular form of V-ATPase, made of specific subunits isoforms, has been located at the plasma membrane of intercalated cells (IC). Mutations in genes encoding IC-specific subunits cause infant distal renal tubular acidosis (dRTA), suggesting that the segmental distribution of these subunits is acquired at birth or during early infancy. However, the comparative ontogeny of the IC-specific versus the ubiquitous subunits of V-ATPase and the mechanisms involved in their segmental expression remain unknown. Real-time reverse transcription-PCR, in situ hybridization, immunoblotting, immunostaining, and subcellular fractionation analyses characterized the expression and distribution of V-ATPase subunits, transcription factors, and differentiation markers during mouse nephrogenesis. Ubiquitous A, E1, B2, G1, and C1 subunits showed an early (embryonic day 13.5 [E13.5]) and stable expression throughout nephrogenesis, followed by a slight increase around birth. The developmental pattern of a1 was bimodal, with early induction, gradual decrease during organogenesis, and neonatal increase. These patterns contrasted with the later (from E15.5) and progressive expression of IC-specific a4, B1, G3, and C2 subunits, after the induction of the forkhead transcription factor Foxi1. From E15.5, Foxi1 mRNA was detected in IC, where it co-distributed with B1 in late nephrogenesis. Immunostaining showed that the distribution of ubiquitous E1 and B2 was acquired from E15.5, whereas a4 was located in IC during late nephrogenesis. Subcellular fractionation showed that in both fetal and mature (cortex and medulla) kidneys, E1 and a4 were located in endosomes. These data demonstrate a differential expression and a coordinate regulation of IC-specific versus ubiquitous V-ATPase subunits during nephrogenesis. They provide new insights into the complex regulation of V-ATPase subunits, the maturation of IC along the nephron, and the pathophysiology of hereditary dRTA.
液泡H(+)-ATP酶(V-ATP酶)是一种普遍存在的多亚基泵,负责细胞内细胞器的酸化。在肾脏中,一种由特定亚基异构体组成的特殊形式的V-ATP酶已定位在闰细胞(IC)的质膜上。编码IC特异性亚基的基因突变会导致婴儿远端肾小管酸中毒(dRTA),这表明这些亚基的节段性分布是在出生时或婴儿早期获得的。然而,V-ATP酶的IC特异性亚基与普遍存在的亚基的比较个体发生以及它们节段性表达所涉及的机制仍然未知。实时逆转录-PCR、原位杂交技术、免疫印迹、免疫染色和亚细胞分级分离分析对小鼠肾发生过程中V-ATP酶亚基、转录因子和分化标志物的表达和分布进行了表征。普遍存在的A、E1、B2、G1和C1亚基在肾发生早期(胚胎第13.5天[E13.5])即有稳定表达,出生前后略有增加。a1的发育模式呈双峰型,早期诱导表达,器官发生过程中逐渐下降,新生儿期增加。这些模式与IC特异性的a4、B1、G3和C2亚基在叉头转录因子Foxi1诱导后(从E15.5开始)的后期及逐渐增加的表达形成对比。从E15.5开始,在IC中检测到Foxi1 mRNA,在肾发生后期它与B1共分布。免疫染色显示,普遍存在的E1和B2的分布从E15.5开始获得,而a4在肾发生后期位于IC中。亚细胞分级分离显示,在胎儿和成熟(皮质和髓质)肾脏中,E1和a4均位于内体中。这些数据表明在肾发生过程中,IC特异性与普遍存在的V-ATP酶亚基存在差异表达和协同调节。它们为V-ATP酶亚基的复杂调节、IC沿肾单位的成熟以及遗传性dRTA的病理生理学提供了新的见解。
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