title: PKC-delta sensitizes Kir3.1/3.2 channels to changes in membrane phospholipid levels after M3 receptor activation in HEK-293 cells.
abstract: G protein-gated inward rectifier (Kir3) channels are inhibited by activation of G(q/11)-coupled receptors and this has been postulated to involve the signaling molecules protein kinase C (PKC) and/or phosphatidylinositol 4,5-bisphosphate (PIP(2)). Their precise roles in mediating the inhibition of this family of channels remain controversial. We examine here their relative roles in causing inhibition of Kir3.1/3.2 channels stably expressed in human embryonic kidney (HEK)-293 cells after muscarinic M(3) receptor activation. In perforated patch mode, staurosporine prevented the G(q/11)-mediated, M(3) receptor, inhibition of channel activity. Recovery from M(3)-mediated inhibition was wortmannin sensitive. Whole cell currents, where the patch pipette was supplemented with PIP(2), were still irreversibly inhibited by M(3) receptor stimulation. When adenosine A(1) receptors were co-expressed, inclusion of PIP(2) rescued the A(1)-mediated response. Recordings from inside-out patches showed that catalytically active PKC applied directly to the intracellular membrane face inhibited the channels: a reversible effect modulated by okadaic acid. Generation of mutant heteromeric channel Kir3.1S185A/Kir3.2C-S178A, still left the channel susceptible to receptor, pharmacological, and direct kinase-mediated inhibition. Biochemically, labeled phosphate is incorporated into the channel. We suggest that PKC-delta mediates channel inhibition because recombinant PKC-delta inhibited channel activity, M(3)-mediated inhibition of the channel, was counteracted by overexpression of two types of dominant negative PKC-delta constructs, and, by using confocal microscopy, we have demonstrated translocation of green fluorescent protein-tagged PKC-delta to the plasma membrane on M(3) receptor stimulation. Thus Kir3.1/3.2 channels are sensitive to changes in membrane phospholipid levels but this is contingent on the activity of PKC-delta after M(3) receptor activation in HEK-293 cells.
authors.affiliation: Dept. of Medicine, University College of London, London WC1E 6JJ, UK. sean.brown@ucl.ac.uk
authors.forename: Sean G
authors.initials: SG
authors.lastname: Brown
authors.forename: Alison
authors.initials: A
authors.lastname: Thomas
authors.forename: Lodewijk V
authors.initials: LV
authors.lastname: Dekker
authors.forename: Andrew
authors.initials: A
authors.lastname: Tinker
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Leaney
mesh_terms: D002460:Cell Line; D002462:Cell Membrane; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010766:Phosphorylation; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D020239:Receptor Cross-Talk / Q000502:physiology*; D043587:Receptor, Muscarinic M3 / Q000502:physiology*
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; C497066:KCNJ3 protein, human; D019269:Phosphatidylinositol 4,5-Diphosphate; D024661:Potassium Channels, Inwardly Rectifying; D043587:Receptor, Muscarinic M3; C497258:PRKCD protein, human; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D043802:GTP-Binding Protein alpha Subunits, Gq-G11