title: Multiple ramp domains are required for generation of amylin receptor phenotype from the calcitonin receptor gene product.
abstract: Calcitonin (CT), calcitonin gene-related peptide (CGRP), amylin, and adrenomedullin constitute a family of structurally related peptides that signal via either the calcitonin receptor-like receptor or the CT receptor, with receptor phenotype determined by coexpression of one of the three receptor activity-modifying proteins (RAMPs). The nature of the interaction between the receptor and RAMP was investigated using chimeras between RAMP1 and RAMP2 where the amino-terminal domain of RAMP1 was attached to the transmembrane domain and carboxy terminus of RAMP2 and called RAMP1/2, and vice versa for RAMP2/1. Cotransfection of wild-type or chimeric RAMPs with the insert-negative isoform of the human CT receptor (hCTR(I1-)) into COS-7 cells resulted in the expression of (125)I-rat amylin binding sites. Highest specific binding was observed when either RAMP1 or RAMP2/1 were cotransfected, indicating the importance of the RAMP transmembrane domain and/or carboxy terminus for the degree to which amylin receptors are expressed. In contrast, the phenotype generated was primarily determined by the amino terminus, with similar RAMP1- and RAMP1/2-induced receptor phenotypes that had higher affinity for human CGRPalpha and lower affinity for human calcitonin than the RAMP2- and RAMP2/1-induced receptors.
authors.affiliation: Molecular Pharmacology Laboratory, Department of Pharmacology, University of Melbourne, Victoria, 3010, Australia.
authors.forename: E T
authors.initials: ET
authors.lastname: Zumpe
authors.forename: N
authors.initials: N
authors.lastname: Tilakaratne
authors.forename: N J
authors.initials: NJ
authors.lastname: Fraser
authors.forename: G
authors.initials: G
authors.lastname: Christopoulos
authors.forename: S M
authors.initials: SM
authors.lastname: Foord
authors.forename: P M
authors.initials: PM
authors.lastname: Sexton
mesh_terms: D000682:Amyloid / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D058228:Islet Amyloid Polypeptide; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D010641:Phenotype; D017433:Protein Structure, Secondary; D011869:Radioligand Assay; D051381:Rats; D058262:Receptor Activity-Modifying Protein 1; D058263:Receptor Activity-Modifying Protein 2; D058261:Receptor Activity-Modifying Proteins; D018003:Receptors, Calcitonin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D058287:Receptors, Islet Amyloid Polypeptide; D018000:Receptors, Peptide / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012474:Salmon; D014162:Transfection
chemical_list: D000682:Amyloid; D047908:Intracellular Signaling Peptides and Proteins; D058228:Islet Amyloid Polypeptide; D008565:Membrane Proteins; C545502:RAMP1 protein, human; C545503:RAMP2 protein, human; C545508:Ramp1 protein, rat; C545509:Ramp2 protein, rat; D058262:Receptor Activity-Modifying Protein 1; D058263:Receptor Activity-Modifying Protein 2; D058261:Receptor Activity-Modifying Proteins; D018003:Receptors, Calcitonin; D058287:Receptors, Islet Amyloid Polypeptide; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins