Journal article
Regions of melanocortin 2 (MC2) receptor accessory protein necessary for dual topology and MC2 receptor trafficking and signaling
The Journal of biological chemistry, Vol.284(1), pp.610-618
01/02/2009
DOI: 10.1074/jbc.M804413200
PMCID: PMC2610514
PMID: 18981183
Abstract
MRAP, melanocortin 2 (MC2) receptor accessory protein, is required for trafficking by the MC2 (ACTH) receptor. MRAP is a single transmembrane protein that forms highly unusual antiparallel homodimers. We used molecular complementation to ask where MRAP achieves dual topology. Fragments of yellow fluorescent protein (YFP) were fused to the NH2 or COOH terminus of MRAP such that YFP fluorescence could occur only in antiparallel homodimers; fluorescence was present in the endoplasmic reticulum. MRAP retained dual topology after deletion of most of the amino terminus. In contrast, deletion of residues 31-37, just NH2-terminal to the transmembrane domain, forced MRAP into a single Nexo/Ccyt orientation and blocked its ability to promote MC2 receptor trafficking and homodimerize. When the transmembrane domain of MRAP was replaced with the corresponding region from RAMP3, dual topology was retained but MRAP was inactive. Insertion of MRAP residues 29-37 conferred dual topology to RAMP3, normally in an Nexo/Ccyt orientation. When expressed with MRAPDelta1-30, MRAPDelta10-20, or MRAPDelta21-30, MC2 receptor was localized on the plasma membrane but unable to respond to ACTH. Residues 18-21 of MRAP were critical; MC2 receptor expressed with MRAP(18-21A) localized to the plasma membrane but did not bind 125I-ACTH or increase cAMP in response to ACTH. A newly identified MRAP homolog, MRAP2, lacks amino acids 18LDYI21 of MRAP and, like MRAP(18-21A), allows MC2 receptor trafficking but not signaling. MRAP2 with an LDYI insertion functions like MRAP. These results demonstrate that MRAP not only facilitates MC2 receptor trafficking but also allows properly localized receptor to bind ACTH and consequently signal.
Details
- Title: Subtitle
- Regions of melanocortin 2 (MC2) receptor accessory protein necessary for dual topology and MC2 receptor trafficking and signaling
- Creators
- Julien A Sebag - Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USAPatricia M Hinkle
- Resource Type
- Journal article
- Publication Details
- The Journal of biological chemistry, Vol.284(1), pp.610-618
- DOI
- 10.1074/jbc.M804413200
- PMID
- 18981183
- PMCID
- PMC2610514
- NLM abbreviation
- J Biol Chem
- ISSN
- 0021-9258
- eISSN
- 1083-351X
- Publisher
- United States
- Grant note
- R01 DK019974 / NIDDK NIH HHS DK19974 / NIDDK NIH HHS
- Language
- English
- Date published
- 01/02/2009
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute
- Record Identifier
- 9984025332802771
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