Article

Molecular Basis of Association of Receptor Activity-Modifying Protein 3 with the Family B G Protein-Coupled Secretin Receptor

Department of Molecular Pharmacology , Mayo Clinic, Scottsdale, Arizona 85259
# Drug Discovery Biology Laboratory, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Melbourne 3800, Australia
Biochemistry, 2009, 48 (49), pp 11773–11785
DOI: 10.1021/bi901326k
Publication Date (Web): November 3, 2009
Copyright © 2009 American Chemical Society
*Address for all the correspondence to Laurence J. Miller, MD, Mayo Clinic, 13400 East Shea Blvd, Scottsdale, AZ 85259. Tel.: (480) 301-6650. Fax: (480) 301-6969. E-mail: [email protected].

  Funding Statement

This work was supported by grants from the National Institutes of Health, DK46577 (L.J.M.), the National Health and Medical Research Council of Australia (NHMRC), 436781 and 519461 (P.M.S.) and from the Fiterman Foundation (L.J.M.). P.M.S. is a Principal Research Fellow of the NHMRC.

Abstract

Abstract Image

The three receptor activity-modifying proteins (RAMPs) have been recognized as being important for the trafficking and function of a subset of family B G protein-coupled receptors, although the structural basis for this has not been well established. In the current work, we use morphological fluorescence techniques, bioluminescence resonance energy transfer, and bimolecular fluorescence complementation to demonstrate that the secretin receptor associates specifically with RAMP3, but not with RAMP1 or RAMP2. We use truncation constructs, peptide competition experiments, and chimeric secretin−GLP1 receptor constructs to establish that this association is structurally specific, dependent on the intramembranous region of the RAMP and TM6 and TM7 of this receptor. There were no observed changes in secretin-stimulated cAMP, intracellular calcium, ERK1/2 phosphorylation, or receptor internalization in receptor-bearing COS or CHO-K1 cells in the presence or absence of exogenous RAMP transfection, although the secretin receptor trafficks normally to the cell surface in these cells in a RAMP-independent manner, resulting in both free and RAMP-associated receptor on the cell surface. RAMP3 association with this receptor was shown to be capable of rescuing a receptor mutant (G241C) that is normally trapped intracellularly in the biosynthetic machinery. Similarly, secretin receptor expression had functional effects on adrenomedullin activity, with increasing secretin receptor expression competing for RAMP3 association with the calcitonin receptor-like receptor to yield a functional adrenomedullin receptor. These data provide important new insights into the structural basis for RAMP3 interaction with a family B G protein-coupled receptor, potentially providing a highly selective target for drug action. This may be representative of similar interactions between other members of this receptor family and RAMP proteins.

Supplemental data are available that show the alignment of the sequences of the human secretin and GLP1 receptors that was utilized to determine the sequences of the chimeric receptor constructs used in the current report. This material is available free of charge via the Internet at

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Received 30 July 2009
Published online 3 November 2009
Published in print 15 December 2009
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