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Constitutive activation of the opioid receptor‐like (ORL 1 ) receptor by mutation of Asn133 to tryptophan in the third transmembrane region
Author(s) -
Kam Kenneth W. L.,
New David C.,
Wong Yung H.
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2002.01231.x
Subject(s) - receptor , mutant , enzyme linked receptor , 5 ht5a receptor , hek 293 cells , transmembrane domain , biology , microbiology and biotechnology , point mutation , g protein coupled receptor , transmembrane protein , mutation , nociceptin receptor , signal transduction , radioligand , biochemistry , gene , opioid , opioid peptide
We have introduced a series of point mutations into the human opioid receptor‐like (ORL 1 ) receptor and characterized them for their ability to constitutively activate G protein‐coupled receptor signalling pathways. Among the 12 mutants generated, mutation at Asn133 (N133W) gave increased basal signalling through three separate pathways. N133W increased the basal activity of G 14 ‐ and G 16 ‐dependent pathways by two‐ to three‐fold. The constitutive activity of the mutant was confirmed by the finding that the enhanced activity is dependent on the level of receptor expression. In HEK‐293 cells stably expressing N133W, signalling through G i/o ‐dependent pathways was also observed. Radioligand binding studies revealed that the affinity for nociceptin of the wild‐type ORL 1 receptor and the N133W mutant do not differ significantly, suggesting that the ligand binding and signalling functions of constitutively active mutants of G protein‐coupled receptors are not necessarily intrinsically linked. In conclusion, our results demonstrate that a mutation in the third transmembrane domain is able to increase the basal signalling activity of the human ORL 1 receptor.