title: ATP modulates Ca2+ uptake by TRPV6 and is counteracted by isoform-specific phosphorylation.
abstract: Ca(2+) homeostasis requires balanced uptake and extrusion, and dysregulation leads to disease. TRPV6 channels are homeostasis regulators, are upregulated in certain cancers, and show an unusual allele-specific evolution in humans. To understand how Ca(2+) uptake can be adapted to changes in metabolic status, we investigate regulation of Ca(2+)-influx by ATP and phosphorylation. We show that ATP binds to TRPV6, reduces whole-cell current increments, and prevents channel rundown with an EC(50) of 380 microM. By using both biochemical binding studies and patch-clamp analyses of wild-type and mutant channels, we have mapped one relevant site for regulation by ATP to residues within the ankyrin repeat domain (ARD) and identify an additional C-terminal binding region. Stimulation of PKC largely prevented the effects of ATP. This regulation requires PKC(betaII) and defined phosphorylation sites within the ARD and the C-terminus. Both regulatory sites act synergistically to constitute a novel mechanism by which ATP stabilizes channel activity and acts as a metabolic switch for Ca(2+) influx. Decreases in ATP concentration or activation of PKC(betaII) disable regulation of the channels by ATP, rendering them more susceptible to inactivation and rundown and preventing Ca(2+) overload.
authors.affiliation: Department of Pharmacology and Toxicology, University of Saarland, 66421 Homburg, Germany.
authors.forename: Dalia
authors.initials: D
authors.lastname: Al-Ansary
authors.forename: Ivan
authors.initials: I
authors.lastname: Bogeski
authors.forename: Barbara M J
authors.initials: BM
authors.lastname: Disteldorf
authors.forename: Ute
authors.initials: U
authors.lastname: Becherer
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Niemeyer
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D064546:Protein Kinase C beta; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D007527:Isoenzymes; D050916:TRPV Cation Channels; C422827:TRPV6 protein, human; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D002118:Calcium