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Uromodulin is expressed in the distal convoluted tubule, where it is critical for regulation of the sodium chloride cotransporter NCC


Tokonami, Natsuko; Takata, Tomoaki; Beyeler, Jan; Ehrbar, Iris; Yoshifuji, Ayumi; Christensen, Erik I; Loffing, Johannes; Devuyst, Olivier; Olinger, Eric G (2018). Uromodulin is expressed in the distal convoluted tubule, where it is critical for regulation of the sodium chloride cotransporter NCC. Kidney International, 94(4):701-715.

Abstract

Uromodulin, the most abundant protein in normal urine, is essentially produced by the cells lining the thick ascending limb. There it regulates the activity of the cotransporter NKCC2 and is involved in sodium chloride handling and blood pressure regulation. Conflicting reports suggested that uromodulin may also be expressed in the distal convoluted tubule (DCT) where its role remains unknown. Using microdissection studies combined with fluorescent in situ hybridization and co-immunostaining analyses, we found a significant expression of uromodulin in mouse and human DCT at approximately 10% of thick ascending limb expression levels, but restricted to the early part of the DCT (DCT1). Genetic deletion of Umod in mouse was reflected by a major shift in NCC activity from the DCT1 to the downstream DCT2 segment, paralleled by a compensatory expansion of DCT2. By increasing the distal sodium chloride and calcium ion load with chronic furosemide administration, an intrinsic compensatory defect in the DCT from Umod-/- compared to wild type mice was found manifested as sodium wasting and hypercalciuria. In line, co-expression studies in HEK cells suggested a facilitating role for uromodulin in NCC phosphorylation, possibly via SPAK-OSR1 modulation. These experiments demonstrate a significant expression of uromodulin in the early part of mouse and human DCT. Thus, biosynthesis of uromodulin in the DCT1 is critical for its function, structure and plasticity, suggesting novel links between uromodulin, blood pressure control and risk of kidney stones.

Abstract

Uromodulin, the most abundant protein in normal urine, is essentially produced by the cells lining the thick ascending limb. There it regulates the activity of the cotransporter NKCC2 and is involved in sodium chloride handling and blood pressure regulation. Conflicting reports suggested that uromodulin may also be expressed in the distal convoluted tubule (DCT) where its role remains unknown. Using microdissection studies combined with fluorescent in situ hybridization and co-immunostaining analyses, we found a significant expression of uromodulin in mouse and human DCT at approximately 10% of thick ascending limb expression levels, but restricted to the early part of the DCT (DCT1). Genetic deletion of Umod in mouse was reflected by a major shift in NCC activity from the DCT1 to the downstream DCT2 segment, paralleled by a compensatory expansion of DCT2. By increasing the distal sodium chloride and calcium ion load with chronic furosemide administration, an intrinsic compensatory defect in the DCT from Umod-/- compared to wild type mice was found manifested as sodium wasting and hypercalciuria. In line, co-expression studies in HEK cells suggested a facilitating role for uromodulin in NCC phosphorylation, possibly via SPAK-OSR1 modulation. These experiments demonstrate a significant expression of uromodulin in the early part of mouse and human DCT. Thus, biosynthesis of uromodulin in the DCT1 is critical for its function, structure and plasticity, suggesting novel links between uromodulin, blood pressure control and risk of kidney stones.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Anatomy
04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Uncontrolled Keywords:Na(+)/Cl(−)-cotransporter, blood pressure regulation, distal convoluted tubule, salt handling, uromodulin
Language:English
Date:1 October 2018
Deposited On:06 Aug 2018 14:22
Last Modified:21 Sep 2018 01:02
Publisher:Elsevier
ISSN:0085-2538
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1016/j.kint.2018.04.021
PubMed ID:30007527

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