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Classes of calcium sensing receptor inactivating mutations define trafficking defects
Author(s) -
Breitwieser Gerda E.,
White Elissa
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.812.8
Subject(s) - endoplasmic reticulum , calcium sensing receptor , allosteric regulation , microbiology and biotechnology , allosteric modulator , mutant , endoplasmic reticulum associated protein degradation , mutation , mg132 , g protein coupled receptor , chemistry , extracellular , receptor , biology , biochemistry , proteasome , calcium , proteasome inhibitor , unfolded protein response , calcium metabolism , gene , organic chemistry
The calcium sensing receptor (CaR) is a Family C GPCR that translates changes in extracellular Ca 2+ into diverse intracellular signals. Inactivating mutations in human CaR cause Ca 2+ handling diseases including familial hypocalciuric hypercalcemia (FHH), neonatal severe hyperparathyroidism (NSHPT). During biosynthesis, CaR must navigate a number of quality control checkpoints, including glycosylation and dimerization, or be shunted to the endoplasmic reticulum‐associated degradation pathway. We have shown that CaR must also navigate a conformational or functional checkpoint in the ER, i,e., activating mutations and/or an allosteric agonist protect against degradation and increase plasma membrane CaR while inactivating mutations and/or an allosteric antagonist increase ERAD. We have examined the biosynthesis of CaR mutations causing FHH/NSHPT by immunoprecipitation, biotinylation, and functional assays. We define several classes of CaR mutants based on rescue of total expression and plasma membrane localization upon treatment with the proteasomal inhibitor MG132. Most interesting are the CaR mutants which show both increased total expression and enhanced plasma membrane localization with MG132, permitting assay of functional activity. Some inactivating mutations of CaR cause a trafficking defect which can be corrected by either proteasome inhibition or treatment with allosteric agonist. Supported by NIH GM077563.