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D-glucose acts via sodium/glucose cotransporter 1 to increase NHE3 in mouse jejunal brush border by a Na+/H+ exchange regulatory factor 2-dependent process.


ABSTRACT:

Background & aims

Oral rehydration solutions reduce diarrhea-associated mortality. Stimulated sodium absorption by these solutions is mediated by the Na(+)/H(+) hydrogen exchanger NHE3 and is increased by Na(+)-glucose co-transport in vitro, but the mechanisms of this up-regulated process are only partially understood.

Methods

Intracellular pH was measured in jejunal enterocytes of wild-type mice and mice with disrupted Na+/H+ exchange regulatory co-factor 2 (NHERF2-/- mice) by multiphoton microscopy. Diarrhea was induced by cholera toxin. Caco-2BBe cells that express NHE3 and the sodium/glucose cotransporter 1 (SGLT1) were studied by fluorometry, before and after siRNA-mediated knockdown of NHERF1 or NHERF2. NHE3 distribution was assessed by cell-surface biotinylation and confocal microscopy. Brush-border mobility was determined by fluorescence recovery after photobleaching and confocal microscopy.

Results

The nonmetabolized SGLT1 substrate ?-methyl-D-Glu (?-MD-G) activated jejunal NHE3; this process required Akt and NHERF2. ?-MD-G normalized NHE3 activity after cholera toxin-induced diarrhea. ?-MD-G-stimulated jejunal NHE3 activity was defective in NHERF2-/- mice and cells with NHERF2 knockdown, but occurred normally with NHERF1 knockdown; was associated with increased NHE3 surface expression in Caco-2 cells, which also was NHERF2-dependent; was associated with dissociation of NHE3 from NHERF2 and an increase in the NHE3 mobile fraction from the brush border; and was accompanied by a NHERF2 ezrin-radixin-moesin-binding domain-dependent increase in co-precipitation of ezrin with NHE3.

Conclusions

SGLT1-mediated Na-glucose co-transport stimulates NHE3 activity in vivo by an Akt- and NHERF2-dependent signaling pathway. It is associated with increased brush-border NHE3 and association between ezrin and NHE3. Activation of NHE3 corrects cholera toxin-induced defects in Na absorption and might contribute to the efficacy of oral rehydration solutions.

SUBMITTER: Lin R 

PROVIDER: S-EPMC3031713 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Publications

D-glucose acts via sodium/glucose cotransporter 1 to increase NHE3 in mouse jejunal brush border by a Na+/H+ exchange regulatory factor 2-dependent process.

Lin Rong R   Murtazina Rakhilya R   Cha Boyoung B   Chakraborty Molee M   Sarker Rafiquel R   Chen Tian-E TE   Lin Zhihong Z   Hogema Boris M BM   de Jonge Hugo R HR   Seidler Ursula U   Turner Jerrold R JR   Li Xuhang X   Kovbasnjuk Olga O   Donowitz Mark M  

Gastroenterology 20101023 2


<h4>Background & aims</h4>Oral rehydration solutions reduce diarrhea-associated mortality. Stimulated sodium absorption by these solutions is mediated by the Na(+)/H(+) hydrogen exchanger NHE3 and is increased by Na(+)-glucose co-transport in vitro, but the mechanisms of this up-regulated process are only partially understood.<h4>Methods</h4>Intracellular pH was measured in jejunal enterocytes of wild-type mice and mice with disrupted Na+/H+ exchange regulatory co-factor 2 (NHERF2-/- mice) by mu  ...[more]

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