title: Novel receptor partners and function of receptor activity-modifying proteins.
abstract: The receptor activity-modifying proteins (RAMPs) comprise a family of three accessory proteins that heterodimerize with the calcitonin receptor-like receptor (CL receptor) or with the calcitonin receptor (CTR) to generate different receptor phenotypes. However, RAMPs are more widely distributed across cell and tissue types than the CTR and CL receptor, suggesting additional roles for RAMPs in cellular processes. We have investigated the potential for RAMP interaction with a number of Class II G protein-coupled receptors (GPCRs) in addition to the CL receptor and the CTR. Using immunofluorescence confocal microscopy, we demonstrate, for the first time, that RAMPs interact with at least four additional receptors, the VPAC1 vasoactive intestinal polypeptide/pituitary adenylate cyclase-activating peptide receptor with all three RAMPs; the glucagon and PTH1 parathyroid hormone receptors with RAMP2; and the PTH2 receptor with RAMP3. Unlike the interaction of RAMPs with the CL receptor or the CTR, VPAC1R-RAMP complexes do not show altered phenotypic behavior compared with the VPAC1R alone, as determined using radioligand binding in COS-7 cells. However, the VPAC1R-RAMP2 heterodimer displays a significant enhancement of agonist-mediated phosphoinositide hydrolysis with no change in cAMP stimulation compared with the VPAC1R alone. Our findings identify a new functional consequence of RAMP-receptor interaction, suggesting that RAMPs play a more general role in modulating cell signaling through other GPCRs than is currently appreciated.
authors.affiliation: Department of Pharmacology and the Howard Florey Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Arthur
authors.initials: A
authors.lastname: Christopoulos
authors.forename: George
authors.initials: G
authors.lastname: Christopoulos
authors.forename: Maria
authors.initials: M
authors.lastname: Morfis
authors.forename: Madhara
authors.initials: M
authors.lastname: Udawela
authors.forename: Marc
authors.initials: M
authors.lastname: Laburthe
authors.forename: Alain
authors.initials: A
authors.lastname: Couvineau
authors.forename: Kenji
authors.initials: K
authors.lastname: Kuwasako
authors.forename: Nanda
authors.initials: N
authors.lastname: Tilakaratne
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Sexton
mesh_terms: D000818:Animals; D019556:COS Cells; D058286:Calcitonin Receptor-Like Protein; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D019281:Dimerization; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport; D058263:Receptor Activity-Modifying Protein 2; D058264:Receptor Activity-Modifying Protein 3; D058261:Receptor Activity-Modifying Proteins; D018003:Receptors, Calcitonin / Q000378:metabolism*; D018027:Receptors, Glucagon / Q000378:metabolism*; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism; D018005:Receptors, Vasoactive Intestinal Peptide / Q000378:metabolism; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
chemical_list: C545578:CALCRL protein, human; D058286:Calcitonin Receptor-Like Protein; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D020033:Protein Isoforms; C545503:RAMP2 protein, human; C545504:RAMP3 protein, human; D058263:Receptor Activity-Modifying Protein 2; D058264:Receptor Activity-Modifying Protein 3; D058261:Receptor Activity-Modifying Proteins; D018003:Receptors, Calcitonin; D018027:Receptors, Glucagon; D018016:Receptors, Parathyroid Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D019204:GTP-Binding Proteins