Biased μ-opioid receptor agonists diversely regulate lateral mobility and functional coupling of the receptor to its cognate G proteins.
There are some indications that biased μ-opioid ligands may diversely affect μ-opioid receptor (MOR) properties. Here, we used confocal fluorescence recovery after photobleaching (FRAP) to study the regulation by different MOR agonists of receptor movement within the plasma membrane of HEK293 cells stably expressing a functional yellow fluorescent protein (YFP)-tagged μ-opioid receptor (MOR-YFP). We found that the lateral mobility of MOR-YFP was increased by (D-Ala2,N-MePhe4,Gly5-ol)-enkephalin (DAMGO) and to a lesser extent also by morphine but decreased by endomorphin-2. Interestingly, cholesterol depletion strongly enhanced the ability of morphine to elevate receptor mobility but significantly reduced or even eliminated the effect of DAMGO and endomorphin-2, respectively. Moreover, the ability of DAMGO and endomorphin-2 to influence MOR-YFP movement was diminished by pertussis toxin treatment. The results obtained by agonist-stimulated [35S]GTPγS binding assays indicated that DAMGO exhibited higher efficacy than morphine and endomorphin-2 did and that the efficacy of DAMGO, contrary to the latter agonists, was enhanced by cholesterol depletion. Overall, our study provides clear evidence that biased MOR agonists diversely affect receptor mobility in plasma membranes as well as MOR/G protein coupling and that the regulatory effect of different ligands depends on the membrane cholesterol content. These findings help to delineate the fundamental properties of MOR regarding their interaction with biased MOR ligands and cognate G proteins.
Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
Barbora
B
Melkes
Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
Lucie
L
Hejnova
Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic. jiri.novotny@natur.cuni.cz.
Jiri
J
Novotny
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism; D002784:Cholesterol / Q000172:deficiency; D004305:Dose-Response Relationship, Drug; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000378:metabolism / Q000494:pharmacology*; D036681:Fluorescence Recovery After Photobleaching; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D009020:Morphine / Q000378:metabolism / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology*; D037342:Pertussis Toxin / Q000494:pharmacology; D021381:Protein Transport; D017450:Receptors, Opioid, mu / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
D001426:Bacterial Proteins; D008024:Ligands; D008164:Luminescent Proteins; D009292:Narcotic Antagonists; D009842:Oligopeptides; D017450:Receptors, Opioid, mu; D011993:Recombinant Fusion Proteins; C054562:yellow fluorescent protein, Bacteria; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C105294:endomorphin 2; D009020:Morphine; D002784:Cholesterol; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go
Biased agonists; Cholesterol; FRAP; G protein coupling; μ-Opioid receptor