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.
Mignen
Olivier
O
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA.
Thompson
Jill L
JL
Shuttleworth
Trevor J
TJ
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