title: Identification of Nipsnap1 as a novel auxiliary protein inhibiting TRPV6 activity.
abstract: The transient receptor potential vanilloid channels 5 and 6 (TRPV5/6) are the most Ca(2+)-selective channels within the TRP superfamily of ion channels. These epithelial Ca(2+) channels are regulated at different intra- and extracellular sites by the feedback response of Ca(2+) itself, calciotropic hormones, and by TRPV5/6-associated proteins. In the present study, bioinformatics was used to search for novel TRPV5/6-associated genes. By including pull-down assays and functional analysis, Nipsnap1-a hitherto functionally uncharacterized globular protein-was identified as a novel factor involved in the regulation of TRPV6. Electrophysiological recordings revealed that Nipsnap1 abolishes TRPV6 currents. Subsequent biotinylation assays showed that TRPV6 plasma membrane expression did not change in the presence of Nipsnap1, suggesting that TRPV6 inhibition by Nipsnap1 is independently regulated from reduced cell surface channel expression. In addition, semi-quantitative reverse transcriptase PCR and immunohistochemical labeling of Nipsnap1 indicated that Nipsnap1 is expressed in mouse intestinal tissues-where TRPV6 is predominantly expressed-but that it does not co-localize with TRPV5 in the kidney. In conclusion, this study presents the first physiological function of Nipsnap1 as an associated protein inhibiting TRPV6 activity that possibly exerts its effect directly at the plasma membrane.
authors.affiliation: Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Joost P H
authors.initials: JP
authors.lastname: Schoeber
authors.forename: Catalin N
authors.initials: CN
authors.lastname: Topala
authors.forename: Kyu Pil
authors.initials: KP
authors.lastname: Lee
authors.forename: Tim T
authors.initials: TT
authors.lastname: Lambers
authors.forename: Guénola
authors.initials: G
authors.lastname: Ricard
authors.forename: Annemiete W C M
authors.initials: AW
authors.lastname: van der Kemp
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Huynen
authors.forename: Joost G J
authors.initials: JG
authors.lastname: Hoenderop
authors.forename: René J M
authors.initials: RJ
authors.lastname: Bindels
mesh_terms: D000595:Amino Acid Sequence; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D019295:Computational Biology; D004594:Electrophysiology; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000235:genetics / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D015220:Calcium Channels; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C113197:NIPSNAP1 protein, human; D011506:Proteins; D050916:TRPV Cation Channels; C492239:TRPV5 protein, human; C422827:TRPV6 protein, human