ATP modulates Ca2+ uptake by TRPV6 and is counteracted by isoform-specific phosphorylation

Ca2+ homeostasis requires balanced uptake and extrusion, and dysregulation leads to disease. TRPV6 channels are homeostasis regulators, are up-regulated in certain cancers, and show an unusual allelespecific evolution in humans. To understand how Ca2+ uptake can be adapted to changes in metabolic status, we investigate regulation of Ca2+-influx by ATP and phosphorylation. We show that ATP binds to TRPV6, reduces whole-cell current increments, and prevents channel rundown with an EC50 of 380 mu M. 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 beta II 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 Ca2+ influx. Decreases in ATP concentration or activation of PKC beta II disable regulation of the channels by ATP, rendering them more susceptible to inactivation and rundown and preventing Ca2+ overload.-Al-Ansary, D., Bogeski, I., Disteldorf, B. M. J., Becherer, U., Niemeyer, B. A. ATP modulates Ca2+ uptake by TRPV6 and is counteracted by isoform-specific phosphorylation. FASEB J. 24, 425-435 (2010). www.fasebj.org