| Rescue of calcium-sensing receptor mutants by allosteric modulators reveals a conformational checkpoint in receptor biogenesis. | |
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MedLine Citation:
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PMID: 17284438 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The calcium-sensing receptor (CaR), a member of G protein-coupled receptor family C, regulates systemic calcium homeostasis by activating G(q)- and G(i)-linked signaling in the parathyroid, kidney, and intestine. CaR is ubiquitinated by the E3 ligase dorfin and degraded via the endoplasmic reticulum-associated degradation pathway (Huang, Y., Niwa, J., Sobue, G., and Breitwieser, G. E. (2006) J. Biol. Chem. 281, 11610-11617). Here we provide evidence for a conformational or functional checkpoint in CaR biogenesis using two complementary approaches. First we characterized the sensitivity of loss- or gain-of-function CaR mutants to proteasome inhibition by MG132. The stabilization of loss-of-function mutants and insensitivity of gain-of-function mutants to MG132 suggests that receptor sensitivity to calcium influences susceptibility to proteasomal degradation. Second, we used the allosteric activator NPS R-568 and antagonist NPS 2143 to promote the active and inactive conformations of wild type CaR, respectively. Overnight culture in NPS R-568 increased expression of CaR, whereas NPS 2143 had the opposite effect. NPS R-568 and NPS 2143 differentially regulated maturation and cell surface expression of wild type CaR, directly affecting maximal signaling responses. NPS R-568 rescued expression of loss-of-function CaR mutants, increasing plasma membrane expression and ERK1/2 phosphorylation in response to 5 mM Ca(2+). Disorders of calcium homeostasis caused by CaR mutations may therefore result from altered receptor biogenesis independent of receptor function, i.e. a protein folding disorder. The allosteric modulators NPS R-568 and NPS 2143 not only alter CaR sensitivity to calcium and hence signaling but also modulate receptor expression. |
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Authors:
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Ying Huang; Gerda E Breitwieser |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't Date: 2007-02-06 |
Journal Detail:
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Title: The Journal of biological chemistry Volume: 282 ISSN: 0021-9258 ISO Abbreviation: J. Biol. Chem. Publication Date: 2007 Mar |
Date Detail:
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Created Date: 2007-03-26 Completed Date: 2007-05-10 Revised Date: 2007-12-03 |
Medline Journal Info:
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Nlm Unique ID: 2985121R Medline TA: J Biol Chem Country: United States |
Other Details:
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Languages: eng Pagination: 9517-25 Citation Subset: IM |
Affiliation:
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Department of Biology, Syracuse University, Syracuse, New York 13244, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Allosteric Regulation
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genetics,
physiology Cell Line Humans Mutagenesis, Site-Directed* Point Mutation* Proteasome Endopeptidase Complex / metabolism, physiology Protein Conformation Protein Folding Receptors, Calcium-Sensing / biosynthesis*, genetics* |
| Grant Support | |
ID/Acronym/Agency:
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GM077563/GM/NIGMS NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Receptors, Calcium-Sensing; EC 3.4.25.1/Proteasome Endopeptidase Complex |
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