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Expression of renal and intestinal Na/Pi cotransporters in the absence of GABARAP


Reining, S C; Liesegang, A; Betz, H; Biber, J; Murer, H; Hernando, N (2010). Expression of renal and intestinal Na/Pi cotransporters in the absence of GABARAP. Pflügers Archiv: European Journal of Physiology (Pflugers Archiv), 460(1):207-217.

Abstract

We have recently shown that the abundance of the renal sodium (Na)/inorganic phosphate (Pi) cotransporter NaPi-IIa is increased in the absence of the GABA(A) receptor-associated protein (GABARAP). Accordingly, GABARAP-deficient mice have a reduced urinary excretion of Pi. However, their circulating levels of Pi do not differ from wild-type animals, suggesting the presence of a compensatory mechanism responsible for keeping serum Pi values constant. Here, we aimed first to identify the molecular basis of this compensation by analyzing the expression of Na/Pi cotransporters known to be expressed in the kidney and intestine. We found that, in the kidney, the upregulation of NaPi-IIa is not accompanied by changes on the expression of either NaPi-IIc or PiT2, the other cotransporters known to participate in renal Pi reabsorption. In contrast, the intestinal expression of NaPi-IIb is downregulated in mutant animals, suggesting that a reduced intestinal absorption of Pi could contribute to maintain a normophosphatemic status despite the increased renal retention. The second goal of this work was to study whether the alterations on the expression of NaPi-IIa induced by chronic dietary Pi are impaired in the absence of GABARAP. Our data indicate that, in response to high Pi diets, GABARAP-deficient mice downregulate the expression of NaPi-IIa to levels comparable to those seen in wild-type animals. However, in response to low Pi diets, the upregulation of NaPi-IIa is greater in the mutant mice. Thus, both the basal expression and the dietary-induced upregulation of NaPi-IIa are increased in the absence of GABARAP.

Abstract

We have recently shown that the abundance of the renal sodium (Na)/inorganic phosphate (Pi) cotransporter NaPi-IIa is increased in the absence of the GABA(A) receptor-associated protein (GABARAP). Accordingly, GABARAP-deficient mice have a reduced urinary excretion of Pi. However, their circulating levels of Pi do not differ from wild-type animals, suggesting the presence of a compensatory mechanism responsible for keeping serum Pi values constant. Here, we aimed first to identify the molecular basis of this compensation by analyzing the expression of Na/Pi cotransporters known to be expressed in the kidney and intestine. We found that, in the kidney, the upregulation of NaPi-IIa is not accompanied by changes on the expression of either NaPi-IIc or PiT2, the other cotransporters known to participate in renal Pi reabsorption. In contrast, the intestinal expression of NaPi-IIb is downregulated in mutant animals, suggesting that a reduced intestinal absorption of Pi could contribute to maintain a normophosphatemic status despite the increased renal retention. The second goal of this work was to study whether the alterations on the expression of NaPi-IIa induced by chronic dietary Pi are impaired in the absence of GABARAP. Our data indicate that, in response to high Pi diets, GABARAP-deficient mice downregulate the expression of NaPi-IIa to levels comparable to those seen in wild-type animals. However, in response to low Pi diets, the upregulation of NaPi-IIa is greater in the mutant mice. Thus, both the basal expression and the dietary-induced upregulation of NaPi-IIa are increased in the absence of GABARAP.

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7 citations in Web of Science®
10 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Center for Integrative Human Physiology
05 Vetsuisse Faculty > Institute of Animal Nutrition
04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
630 Agriculture
Language:English
Date:June 2010
Deposited On:06 Jul 2010 14:04
Last Modified:05 Apr 2016 14:10
Publisher:Springer
ISSN:0031-6768
Publisher DOI:https://doi.org/10.1007/s00424-010-0832-2
PubMed ID:20354864

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