Interaction of the epithelial Ca2+ channels TRPV5 and TRPV6 with the intestine- and kidney-enriched PDZ protein NHERF4.
The epithelial Ca(2+) channels TRPV5 and TRPV6 constitute the apical Ca(2+) influx pathway in epithelial Ca(2+) transport. PDZ proteins have been demonstrated to play a crucial role in the targeting or anchoring of ion channels and transporters in the apical domain of the cell. In this study, we describe the identification of NHERF4 (Na-P(i) Cap2/IKEPP/PDZK2) as a novel TRPV5- and TRPV6-associated PDZ protein. NHERF4 was identified using two separate yeast two-hybrid screens with the carboxyl termini of TRPV5 and TRPV6 as bait. Binding of the carboxyl termini of TRPV5 and TRPV6 with NHERF4 was confirmed by GST pull-down assays using in-vitro-translated NHERF4 or lysates of Xenopus laevis oocytes expressing NHERF4. Furthermore, the interaction was confirmed by GST pull-down and co-immunoprecipitation assays using in-vitro-translated full-length TRPV5 and Xenopus oocytes or HEK293 cells co-expressing NHERF4 and TRPV5/TRPV6, respectively. The fourth PDZ domain of NHERF4 was sufficient for the interaction, although PDZ domain 1 also contributed to the binding. The binding site for NHERF4 localized in a conserved region in the carboxyl terminus of TRPV5 and was distinct from the binding site of the PDZ protein NHERF2. NHERF4 predominantly localized at the plasma membrane of X. laevis oocytes and HeLa cells. This localization was independent of the presence of TRPV5. Therefore, we hypothesize a role for this novel PDZ protein as a putative plasma membrane scaffold for the epithelial Ca(2+) channels.
Cell Physiology, Department of Physiology, 286, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen Medical Center, P.O. Box 9101, NL-6500 HB, Nijmegen, The Netherlands.
Stan F J
SF
van de Graaf
Joost G J
JG
Hoenderop
Annemiete W C M
AW
van der Kemp
Serge M
SM
Gisler
René J M
RJ
Bindels
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism* / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D007413:Intestinal Mucosa / Q000378:metabolism*; D015640:Ion Channel Gating; D007668:Kidney / Q000378:metabolism*; D051379:Mice; D009865:Oocytes / Q000502:physiology*; D010750:Phosphoproteins; D025941:Protein Interaction Mapping; D017923:Sodium-Hydrogen Exchangers; D050916:TRPV Cation Channels / Q000378:metabolism*; D014982:Xenopus laevis
D015220:Calcium Channels; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; D050916:TRPV Cation Channels; C120776:TRPV6 channel; C492240:Trpv5 protein, mouse; C093376:sodium-hydrogen exchanger regulatory factor