title: The M(5) muscarinic acetylcholine receptor third intracellular loop regulates receptor function and oligomerization.
abstract: Besides some pharmacological, biochemical and biophysical evidences support the contention that muscarinic acetylcholine receptors can form homo- and heterodimers, the existence of specific M(3) and M(5) muscarinic receptors oligomers in living cells is a new concept. Interestingly, this phenomenon might have relevance in lymphocytic cholinergic function since both T- and B-cells naturally express high levels of these two receptor subtypes. Here, by means of co-immunoprecipitation and bioluminescence resonance energy transfer methods we demonstrated that M(3) and M(5) muscarinic receptors could form constitutive homo- and heterodimers in transiently transfected HEK-293T cells. Interestingly, this receptor-receptor interaction was unaltered by carbachol treatment but it was affected by the expression of a peptide corresponding to a portion of the third intracellular loop of the M(5) muscarinic receptor. In addition, the same peptide was able to abrogate the carbachol-induced mitogen-activated protein kinase phosphorylation and the carbachol-enhanced PHA-induced IL-2 production in derived lymphocytic T cells. Overall, these results suggest that the third intracellular loop of the M(5) muscarinic receptor might play a regulatory role in receptor function and heteromerization, thus providing the molecular framework for a potential cholinergic-based therapeutic intervention of the immune system.
authors.affiliation: Centre de Biotecnologia Molecular, Department d'Enginyeria Química, Universitat Politècnica de Catalunya, Terrassa, 08222 Barcelona, Spain; Neuroscience Department, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Dasiel O
authors.initials: DO
authors.lastname: Borroto-Escuela
authors.forename: Gloria
authors.initials: G
authors.lastname: García-Negredo
authors.forename: Pere
authors.initials: P
authors.lastname: Garriga
authors.forename: Kjell
authors.initials: K
authors.lastname: Fuxe
authors.forename: Francisco
authors.initials: F
authors.lastname: Ciruela
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D043587:Receptor, Muscarinic M3 / Q000378:metabolism; D043642:Receptor, Muscarinic M5 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism
chemical_list: D043587:Receptor, Muscarinic M3; D043642:Receptor, Muscarinic M5; D011993:Recombinant Fusion Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D010738:Type C Phospholipases