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Functions of Transmembrane Domain 6 in Human Melanocortin‐4 Receptor
Author(s) -
Fan ZhenChuan,
Tao YaXiong
Publication year - 2009
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.23.1_supplement.943.4
Subject(s) - melanocortin 4 receptor , transmembrane domain , mutant , receptor , agonist , transmembrane protein , energy homeostasis , melanocortin , microbiology and biotechnology , mutagenesis , wild type , alanine scanning , g protein coupled receptor , alanine , chemistry , signal transduction , biology , gene , biochemistry , amino acid
The melanocortin‐4 receptor (MC4R) is a G protein‐coupled receptor critically involved in regulating energy homeostasis. Activation of the MC4R leads to decreased food intake and increased energy expenditure. Loss‐of‐function mutations in the MC4R gene were the most common form of monogenic obesity. Despite the important therapeutic potential of the MC4R in obesity treatment, the structure‐function relationship has not been adequately investigated. In this study, we investigated the functions of the transmembrane domain (TM) 6 of the MC4R using alanine‐scanning mutagenesis. A total of 31 mutants were generated. The ligand binding and signaling properties of these mutants were measured. Maximal binding capacities were decreased by 50% for P260A, F261A, H264A, L265A, Y268A, and S270A compared to the wild type MC4R. Maximal signaling after stimulation with the superpotent agonist NDP‐MSH was decreased for I266A and F267A. Six mutants located at the cytoplasmic half of TM6, including M241A, I245A, T246A, T248A, I249A, and L250A, have significantly increased constitutive activities, suggesting that these residues are important for constraining the wild type MC4R in inactive conformation. In summary, we identified six residues at the cytoplasmic end of TM6 that are important for constraining the WT MC4R in inactive conformation, and F267 as critical for agonist‐stimulated signaling.