title: Inhibition of G protein-coupled receptor trafficking in neuroblastoma cells by MAP 4 decoration of microtubules.
abstract: One mechanism for the reappearance of G protein-coupled receptors after agonist activation is microtubule-based transport. In pressure-overload cardiac hypertrophy, there is downregulation of G protein-coupled receptors and the appearance of a densified microtubule network extensively decorated by a microtubule-associated protein, MAP 4. Our hypothesis is that overdecoration of a dense microtubule network with this structural protein, as in hypertrophied myocardium, would impede receptor recovery. We tested this hypothesis by studying muscarinic acetylcholine receptor (mAChR) internalization and recovery after agonist stimulation in neuroblastoma cells. Exposure of cells to carbachol, a muscarinic receptor agonist, decreased membrane receptor binding activity. After carbachol withdrawal, receptor binding recovered toward the initial value. When microtubules were depolymerized before carbachol withdrawal, mAChR recovery was only 44% of that in intact cells. Cells were then infected with an adenovirus containing MAP 4 cDNA. MAP 4 protein decorated the microtubules extensively, and receptor recovery upon carbachol withdrawal was reduced to 54% of control. Thus muscarinic receptor recovery after agonist exposure is microtubule dependent, and MAP 4 decoration of microtubules inhibits receptor recovery.
authors.affiliation: Cardiology Division, Gazes Cardiac Research Institute, Medical University of South Carolina, Charleston 29401, USA.
authors.forename: Guangmao
authors.initials: G
authors.lastname: Cheng
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iijima
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ishibashi
authors.forename: Dhandapani
authors.initials: D
authors.lastname: Kuppuswamy
authors.forename: George
authors.initials: G
authors.lastname: Cooper
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D005456:Fluorescent Dyes; D019204:GTP-Binding Proteins / Q000378:metabolism*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D018721:Muscarinic Agonists / Q000494:pharmacology; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D005456:Fluorescent Dyes; D008869:Microtubule-Associated Proteins; D018721:Muscarinic Agonists; D011956:Receptors, Cell Surface; D011976:Receptors, Muscarinic; D002217:Carbachol; D019204:GTP-Binding Proteins