Defective coupling of apical PTH receptors to phospholipase C prevents internalization of the Na+-phosphate cotransporter NaPi-IIa in Nherf1-deficient mice.
Phosphate reabsorption in the renal proximal tubule occurs mostly via the type IIa Na(+)-phosphate cotransporter (NaP(i)-IIa) in the brush border membrane (BBM). The activity and localization of NaP(i)-IIa are regulated, among other factors, by parathyroid hormone (PTH). NaP(i)-IIa interacts in vitro via its last three COOH-terminal amino acids with the PDZ protein Na(+)/H(+)-exchanger isoform 3 regulatory factor (NHERF)-1 (NHERF1). Renal phosphate reabsorption in Nherf1-deficient mice is altered, and NaP(i)-IIa expression in the BBM is reduced. In addition, it has been proposed that NHERF1 and NHERF2 are important for the coupling of PTH receptors (PTHRs) to phospholipase C (PLC) and the activation of the protein kinase C pathway. We tested the role of NHERF1 in the regulation of NaP(i)-IIa by PTH in Nherf1-deficient mice. Immunohistochemistry and Western blotting demonstrated that stimulation of apical and basolateral receptors with PTH-(1-34) led to internalization of NaP(i)-IIa in wild-type and Nherf1-deficient mice. Stimulation of only apical receptors with PTH-(3-34) failed to induce internalization in Nherf1-deficient mice. Expression and localization of apical PTHRs were similar in wild-type and Nherf1-deficient mice. Activation of the protein kinase C- and A-dependent pathways with 1,2-dioctanoyl-sn-glycerol or 8-bromo-cAMP induced normal internalization of NaP(i)-IIa in wild-type, as well as Nherf1-deficient, mice. Stimulation of PLC activity due to apical PTHRs was impaired in Nherf1-deficient mice. These data suggest that NHERF1 in the proximal tubule is important for PTH-induced internalization of NaP(i)-IIa and, specifically, couples the apical PTHR to PLC.
Capuano
Paola
P
Institute of Physiology, Univ. of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Bacic
Desa
D
Roos
Marcel
M
Gisler
Serge M
SM
Stange
Gerti
G
Biber
Jürg
J
Kaissling
Brigitte
B
Weinman
Edward J
EJ
Shenolikar
Shirish
S
Wagner
Carsten A
CA
Murer
Heini
H
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D004705:Endocytosis; D005260:Female; D066298:In Vitro Techniques; D017136:Ion Transport; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000819:agonists / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology*; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa / Q000378:metabolism*; D019379:Teriparatide / Q000031:analogs & derivatives / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism*
D004075:Diglycerides; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D010710:Phosphates; D010750:Phosphoproteins; D044168:Receptor, Parathyroid Hormone, Type 1; C493555:Slc34a1 protein, mouse; D017923:Sodium-Hydrogen Exchangers; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; C093376:sodium-hydrogen exchanger regulatory factor; C044295:1,2-dioctanoylglycerol; C063551:parathyroid hormone (3-34)amide; D019379:Teriparatide; D015124:8-Bromo Cyclic Adenosine Monophosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; C035748:parathyroid hormone (1-34)amide