Differential roles of NHERF1, NHERF2, and PDZK1 in regulating CFTR-mediated intestinal anion secretion in mice
Anurag Kumar Singh, … , Boris M. Hogema, Ursula Seidler
Anurag Kumar Singh, … , Boris M. Hogema, Ursula Seidler
Published February 16, 2009
Citation Information: J Clin Invest. 2009;119(3):540-550. https://doi.org/10.1172/JCI35541.
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Research Article Gastroenterology

Differential roles of NHERF1, NHERF2, and PDZK1 in regulating CFTR-mediated intestinal anion secretion in mice

Abstract

The epithelial anion channel CFTR interacts with multiple PDZ domain–containing proteins. Heterologous expression studies have demonstrated that the Na+/H+ exchanger regulatory factors, NHERF1, NHERF2, and PDZK1 (NHERF3), modulate CFTR membrane retention, conductivity, and interactions with other transporters. To study their biological roles in vivo, we investigated CFTR-dependent duodenal HCO3– secretion in mouse models of Nherf1, Nherf2, and Pdzk1 loss of function. We found that Nherf1 ablation strongly reduced basal as well as forskolin-stimulated (FSK-stimulated) HCO3– secretory rates and blocked β2-adrenergic receptor (β2-AR) stimulation. Conversely, Nherf2–/– mice displayed augmented FSK-stimulated HCO3– secretion. Furthermore, although lysophosphatidic acid (LPA) inhibited FSK-stimulated HCO3– secretion in WT mice, this effect was lost in Nherf2–/– mice. Pdzk1 ablation reduced basal, but not FSK-stimulated, HCO3– secretion. In addition, laser microdissection and quantitative PCR revealed that the β2-AR and the type 2 LPA receptor were expressed together with CFTR in duodenal crypts and that colocalization of the β2-AR and CFTR was reduced in the Nherf1–/– mice. These data suggest that the NHERF proteins differentially modulate duodenal HCO3– secretion: while NHERF1 is an obligatory linker for β2-AR stimulation of CFTR, NHERF2 confers inhibitory signals by coupling the LPA receptor to CFTR.

Authors

Anurag Kumar Singh, Brigitte Riederer, Anja Krabbenhöft, Brigitte Rausch, Janina Bonhagen, Ulrich Lehmann, Hugo R. de Jonge, Mark Donowitz, Chris Yun, Edward J. Weinman, Olivier Kocher, Boris M. Hogema, Ursula Seidler

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Figure 1

Basal and FSK-stimulated HCO3– secretion in Nherf1–/–, Nherf1–/–Cftr–/–, and WT murine duodenum in vivo.

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Basal and FSK-stimulated HCO3– secretion in Nherf1–/–, Nherf1–/–Cftr–/–,...
(A) Duodenal HCO3– secretion was measured in anesthetized Nherf1–/–, Nherf1–/–Cftr–/–, and WT littermates in the basal state, and during and after 20 min luminal perfusion with 10–4 M FSK. Basal as well as FSK-stimulated duodenal HCO3– secretion was dramatically reduced in the Nherf1–/– and Nherf1–/–Cftr–/– mice compared with WT littermates (n = 6 pairs of KO and WT mice, P < 0.001). The 20-min application time is denoted by shading. *P < 0.01, **P < 0.001, ***P < 0.0001 versus WT; #P < 0.01, ##P < 0.001 versus basal value; †P < 0.01, ††P < 0.001 versus Nherf1–/–. (B) The net peak FSK- stimulated HCO3– secretory rate was significantly lower in Nherf1–/– and Nherf1–/–Cftr–/– mice than in WT littermates. The net peak was calculated for each experiment in this and subsequent experiments by taking the peak value and subtracting the average of the 2 basal values before the application of 10–4 M FSK. *P < 0.01; **P < 0.001; ***P < 0.0001.