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    Pharmacological chaperones increase the cell-surface expression of intracellularly retained mutants of the melanocortin 4 receptor with unique rescuing efficacy profiles


    Ward, Natalie-Anne and Hirst, Simon and Williams, John and Findlay, John B. C. (2012) Pharmacological chaperones increase the cell-surface expression of intracellularly retained mutants of the melanocortin 4 receptor with unique rescuing efficacy profiles. Biochemical Society Transactions, 40. pp. 717-720. ISSN 0300-5127

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    Abstract

    Mutated versions of membrane proteins often fail to express at the plasma membrane, but instead are trapped in the secretory pathway, resulting in disease. The retention of these mutant proteins is thought to result from local misfolding, which prevents export from the ER (endoplasmic reticulum), targeting the receptor for degradation via the ER-associated quality control system. The rhodopsin-like G-proteincoupled MC4R (melanocortin 4 receptor) is an example of such a membrane protein. Over 100 natural MC4R mutations are linked with an obese phenotype and to date represent the most common monogenic cause of severe early-onset obesity. More than 80% of these mutations result in a substantial proportion of MC4R being retained intracellularly. If these receptors were expressed at the plasma membrane, many could be functional, as mutations often occur in regions distinct from those associated with ligand or G-protein binding. Our aim is to show proof of concept that selective compounds can rescue the function of MC4R mutants by increasing their cell-surface expression, and further to this, examine whether the rescue profile differs between mutants. Whole-cell ELISA and 96-well fluorescence-based assays with N-terminally HA (haemagglutinin)-tagged and C-terminally mCherry-tagged mutant MC4Rs were used to screen a number of novel MC4R-selective compounds. A total of four related compounds increased the cell-surface expression of wild-type and three intracellularly retained mutant MC4Rs, thus acting as pharmacological chaperones. There appears to be a unique rescue efficacy profile for each compound that does not correlate with potency, suggesting distinct receptor conformations induced by the different mutations. A degree of functionality of V50M and S58C was also rescued following relocation to the cell surface.

    Item Type: Article
    Additional Information: This paper was presented at the Protein Folding and Misfolding: Mechanisms and Consequences; Irish Area Section Annual Meeting 2011, 1-2 December 2011, Glenroyal Hotel/National University of Ireland Maynooth
    Keywords: cell-surface rescue; intracellular retention; melanocortin 4 receptor (MC4R); pharmacological chaperone; rescue efficacy profile;
    Academic Unit: Faculty of Science and Engineering > Biology
    Item ID: 5993
    Identification Number: https://doi.org/10.1042/BST20110764
    Depositing User: Professor John Findlay
    Date Deposited: 31 Mar 2015 14:47
    Journal or Publication Title: Biochemical Society Transactions
    Publisher: Portland Press
    Refereed: Yes
    URI:

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