Multiple Ramp Domains Are Required for Generation of Amylin Receptor Phenotype from the Calcitonin Receptor Gene Product

• Published in: Biochemical and biophysical research communications Vol. 267; no. 1; pp. 368 - 372
• Main Authors: Zumpe, Emma T., Tilakaratne, Nanda, Fraser, Neil J., Christopoulos, George, Foord, Steven M., Sexton, Patrick M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 07.01.2000
• Subjects: Amyloid - metabolism; Animals; Cercopithecus aethiops; COS Cells; Humans; Intracellular Signaling Peptides and Proteins; Islet Amyloid Polypeptide; Kinetics; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Models, Molecular; Phenotype; Protein Structure, Secondary; Radioligand Assay; Rats; Receptor Activity-Modifying Protein 1; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Proteins; Receptors, Calcitonin - chemistry; Receptors, Calcitonin - genetics; Receptors, Calcitonin - metabolism; Receptors, Islet Amyloid Polypeptide; Receptors, Peptide - genetics; Receptors, Peptide - metabolism; Recombinant Fusion Proteins - metabolism; Salmon; Transfection
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1999.1943

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 (hCTRI1−) into COS-7 cells resulted in the expression of 125I-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 CGRPα and lower affinity for human calcitonin than the RAMP2- and RAMP2/1-induced receptors.