title: 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 beta2-adrenergic receptor (beta2-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 beta2-AR and the type 2 LPA receptor were expressed together with CFTR in duodenal crypts and that colocalization of the beta2-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 beta2-AR stimulation of CFTR, NHERF2 confers inhibitory signals by coupling the LPA receptor to CFTR.
authors.affiliation: Department of Gastroenterology, Hepatology, and Endocrinology, Carl-Neuberg-Strasse 1, Hannover Medical School, Hannover, Germany.
authors.forename: Anurag Kumar
authors.initials: AK
authors.lastname: Singh
authors.forename: Brigitte
authors.initials: B
authors.lastname: Riederer
authors.forename: Anja
authors.initials: A
authors.lastname: Krabbenhöft
authors.forename: Brigitte
authors.initials: B
authors.lastname: Rausch
authors.forename: Janina
authors.initials: J
authors.lastname: Bonhagen
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lehmann
authors.forename: Hugo R
authors.initials: HR
authors.lastname: de Jonge
authors.forename: Mark
authors.initials: M
authors.lastname: Donowitz
authors.forename: Chris
authors.initials: C
authors.lastname: Yun
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Weinman
authors.forename: Olivier
authors.initials: O
authors.lastname: Kocher
authors.forename: Boris M
authors.initials: BM
authors.lastname: Hogema
authors.forename: Ursula
authors.initials: U
authors.lastname: Seidler
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D005576:Colforsin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D004386:Duodenum / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D017353:Gene Deletion; D007419:Intestinal Secretions / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D008246:Lysophospholipids / Q000494:pharmacology; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology*
chemical_list: D000838:Anions; D001639:Bicarbonates; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids; D008565:Membrane Proteins; C514896:PDZK1 protein, mouse; D010750:Phosphoproteins; D018343:Receptors, Adrenergic, beta-2; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; C032881:lysophosphatidic acid