title: Activation of muscarinic m5 receptors inhibits recombinant KCNQ2/KCNQ3 K+ channels expressed in HEK293T cells.
abstract: A variety of G-protein-coupled receptors regulate membrane excitability via M-type K(+) current (M-current) modulation. Muscarinic m1 and m3 acetylcholine receptors have both been implicated in the modulation of M-current. The muscarinic m5 receptor, like muscarinic m1 and m3 receptors, couples to phospholipase C via a pertussis toxin-insensitive G protein. Since a number of other receptors which activate phospholipase C also modulate M-current, we investigated if muscarinic m5 receptors could modulate recombinant M-type (KCNQ2/KCNQ3) K(+) channels after heterologous expression in human embryonic kidney (HEK) 293T cells. Application of Oxo-tremorine M to HEK293T cells expressing muscarinic m1, m3, or m5 receptors produced a similar robust inhibition of M-current, whereas muscarinic m2 and m4 receptor stimulation was without effect. Muscarinic m1, m3, or m5 receptor stimulation decreased the deactivation time constants of M-current at -50 mV. The inhibition of M-current by stimulation of muscarinic m1, m3, or m5 receptors was insensitive to overnight treatment with pertussis toxin or cholera toxin, which interfere with G(i/o) and G(s) G-protein signaling. These data suggest that muscarinic m1, m3, and m5 receptors inhibit M-channels via the activation of a common G protein.
authors.affiliation: Department of Physiology SL-39, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Guo
authors.forename: Geoffery G
authors.initials: GG
authors.lastname: Schofield
mesh_terms: D002460:Cell Line; D002772:Cholera Toxin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D051658:KCNQ2 Potassium Channel; D051659:KCNQ3 Potassium Channel; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010095:Oxotremorine / Q000031:analogs & derivatives* / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D043643:Receptor, Muscarinic M1; D043587:Receptor, Muscarinic M3; D043642:Receptor, Muscarinic M5; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D051658:KCNQ2 Potassium Channel; C496914:KCNQ2 protein, human; D051659:KCNQ3 Potassium Channel; C496916:KCNQ3 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D043643:Receptor, Muscarinic M1; D043587:Receptor, Muscarinic M3; D043642:Receptor, Muscarinic M5; D011976:Receptors, Muscarinic; D010095:Oxotremorine; C042743:oxotremorine M; D002772:Cholera Toxin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins