Arachidonate-regulated Ca2+-selective (ARC) channel activity is modulated by phosphorylation and involves an A-kinase anchoring protein.
In many non-excitable cells, the predominant mode of agonist-activated Ca(2+) entry switches from the arachidonic acid-regulated Ca(2+) (ARC) channels at low agonist concentrations, to store-operated channels at high concentrations. Underlying this process is the inhibition of the ARC channels by a calcineurin-mediated dephosphorylation, which inhibits the ability of arachidonic acid to activate the channels. Following such a dephosphorylation, we found that restoration of the sensitivity of the ARC channels to arachidonic acid, as well as to low concentrations of carbachol, was specifically dependent on protein kinase A (PKA) activity. Inhibition of protein kinase C, protein kinase G or calmodulin-activated kinase had no effect. This action of PKA was unaffected by prolonged intracellular dialysis, whilst disruption of the binding of PKA to A-kinase anchoring proteins (AKAPs) inhibited currents through ARC channels, and blocked the PKA-dependent effects. AKAP79, a protein which scaffolds both PKA and calcineurin, was shown to be present in the cells. These data illustrate the significance of PKA-dependent phosphorylation and calcineurin-dependent dephosphorylation in the overall regulation of ARC channel activity, and indicate the key role of an AKAP, possibly AKAP79, in the spatial organization these processes.
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA.
Olivier
O
Mignen
Jill L
JL
Thompson
Trevor J
TJ
Shuttleworth
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D016718:Arachidonic Acid / Q000494:pharmacology*; D019703:Calcineurin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006801:Humans; D018408:Patch-Clamp Techniques; D010766:Phosphorylation
D048868:Adaptor Proteins, Signal Transducing; D015220:Calcium Channels; D016718:Arachidonic Acid; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D002118:Calcium