title: Role of internalization of M2 muscarinic receptor via clathrin-coated vesicles in desensitization of the muscarinic K+ current in heart.
abstract: In the heart, ACh activates the ACh-activated K(+) current (I(K,ACh)) via the M(2) muscarinic receptor. The relationship between desensitization of I(K,ACh) and internalization of the M(2) receptor has been studied in rat atrial cells. On application of the stable muscarinic agonist carbachol for 2 h, I(K,ACh) declined by approximately 62% with time constants of 1.5 and 26.9 min, whereas approximately 83% of the M(2) receptor was internalized from the cell membrane with time constants of 2.9 and 51.6 min. Transfection of the cells with beta-adrenergic receptor kinase 1 (G protein-receptor kinase 2) and beta-arrestin 2 significantly increased I(K,ACh) desensitization and M(2) receptor internalization during a 3-min application of agonist. Internalized M(2) receptor in cells exposed to carbachol for 2 h was colocalized with clathrin and not caveolin. It is concluded that a G protein-receptor kinase 2- and beta-arrestin 2-dependent internalization of the M(2) receptor into clathrin-coated vesicles could play a major role in I(K,ACh) desensitization.
authors.affiliation: Cardiovascular Research Group, School of Medicine, University of Manchester, Manchester, United Kingdom.
authors.forename: T T
authors.initials: TT
authors.lastname: Yamanushi
authors.forename: Z
authors.initials: Z
authors.lastname: Shui
authors.forename: R N
authors.initials: RN
authors.lastname: Leach
authors.forename: H
authors.initials: H
authors.lastname: Dobrzynski
authors.forename: T W
authors.initials: TW
authors.lastname: Claydon
authors.forename: M R
authors.initials: MR
authors.lastname: Boyett
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D051244:Caveolin 3 / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D018678:Cholinergic Agents / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D022163:Clathrin-Coated Vesicles / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000502:physiology*; D054769:G-Protein-Coupled Receptor Kinase 2; D006321:Heart / Q000294:innervation / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D043585:Receptor, Muscarinic M2 / Q000378:metabolism* / Q000502:physiology; D014162:Transfection; D014630:Vagus Nerve / Q000502:physiology; D051552:beta-Adrenergic Receptor Kinases / Q000235:genetics / Q000378:metabolism; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605257:Arrb2 protein, rat; D019390:Arrestins; C495549:Cav3 protein, rat; D051244:Caveolin 3; D018678:Cholinergic Agents; D018679:Cholinergic Agonists; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D043585:Receptor, Muscarinic M2; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D002217:Carbachol; C496569:Grk2 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D000109:Acetylcholine; D011188:Potassium