Receptor Species-dependent Desensitization Controls KCNQ1/KCNE1 K+ Channels as Downstream Effectors of Gq Protein-coupled Receptors.
Activation of Gqprotein-coupled receptors (GqPCRs) might induce divergent cellular responses, related to receptor-specific activation of different branches of the Gqsignaling pathway. Receptor-specific desensitization provides a mechanism of effector modulation by restricting the spatiotemporal activation of signaling components downstream of GqWe quantified signaling events downstream of GqPCR activation with FRET-based biosensors in CHO and HEK 293 cells. KCNQ1/KCNE1 channels (IKs) were measured as a functional readout of receptor-specific activation. Activation of muscarinic M1receptors (M1-Rs) caused robust and reversible inhibition of IKs.In contrast, activation of α1B-adrenergic receptors (α1B-ARs) induced transient inhibition of IKs, which turned into delayed facilitation after agonist withdrawal. As a novel finding, we demonstrate that GqPCR-specific kinetics of IKsmodulation are determined by receptor-specific desensitization, evident at the level of Gαqactivation, phosphatidylinositol 4,5-bisphosphate (PIP2) depletion, and diacylglycerol production. Sustained IKsinhibition during M1-R stimulation is attributed to robust membrane PIP2depletion, whereas the rapid desensitization of α1B-AR delimits PIP2reduction and augments current activation by protein kinase C (PKC). Overexpression of Ca2+-independent PKCδ did not affect the time course of α1B-AR-induced diacylglycerol formation, excluding a contribution of PKCδ to α1B-AR desensitization. Pharmacological inhibition of Ca2+-dependent PKC isoforms abolished fast α1Breceptor desensitization and augmented IKsreduction, but did not affect IKsfacilitation. These data indicate a contribution of Ca2+-dependent PKCs to α1B-AR desensitization, whereas IKsfacilitation is induced by Ca2+-independent PKC isoforms. In contrast, neither inhibition of Ca2+-dependent/Ca2+-independent isoforms nor overexpression of PKCδ induced M1receptor desensitization, excluding a contribution of PKC to M1-R-induced IKsmodulation.
From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany cecile.kienitz@rub.de.
Marie-Cécile
MC
Kienitz
From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany.
Dilyana
D
Vladimirova
From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany.
Christian
C
Müller
From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany.
Lutz
L
Pott
From the Institute of Physiology, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany.
Andreas
A
Rinne
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D006224:Cricetinae; D003412:Cricetulus; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000235:genetics / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000378:metabolism; D043643:Receptor, Muscarinic M1 / Q000235:genetics / Q000378:metabolism*; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*
C554061:GNAQ protein, human; C489622:KCNE1 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D019269:Phosphatidylinositol 4,5-Diphosphate; D024642:Potassium Channels, Voltage-Gated; D043643:Receptor, Muscarinic M1; D018340:Receptors, Adrenergic, alpha-1; C497258:PRKCD protein, human; D051745:Protein Kinase C-delta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium
IKs; K channel; KCNQ1; PKC; adrenergic receptor; alpha-adrenergic α1B receptor; desensitization; diacylglycerol; fluorescence resonance energy transfer (FRET); ion channel; muscarinic M1 receptor; phosphoinositide; receptor desensitization; signal transduction