MOP and NOP receptor interaction: Studies with a dual expression system and bivalent peptide ligands

• Published in: PloS one 2022-01, Vol.17 (1), p.e0260880
• Main Authors: Bird, M F, McDonald, J, Horley, B, O'Doherty, J P, Fraser, B, Gibson, C L, Guerrini, R, Caló, G, Lambert, D G
• Format: Article
• Language: English
• Subjects: Addiction; Addictions; Adenosine; Agonists; Analgesia; Analgesics; Animals; Binding; Biology and Life Sciences; Cell culture; Critical care; Cyclic AMP; Cyclic AMP - metabolism; Drug abuse; Drug tolerance; Engineering and Technology; Experiments; Fluorescence; Fluorescence resonance energy transfer; Fluorescent indicators; Health aspects; HEK293 Cells; Hippocampus; Humans; Kinases; Ligands; Ligands (Biochemistry); Localization; Medicine and Health Sciences; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; Narcotics; Neurons - metabolism; Nociceptin Receptor; Opioid Peptides - metabolism; Opioid Peptides - pharmacology; Opioid receptors (type mu); Pain management; Pain perception; Peptides; Peptides - chemistry; Peptides - metabolism; Peptides - pharmacology; Physiological aspects; Protein Binding; Receptors; Receptors, Opioid - metabolism; Receptors, Opioid, mu - metabolism; Research and Analysis Methods; Side effects
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0260880

Opioids targeting mu;μ (MOP) receptors produce analgesia in the peri-operative period and palliative care. They also produce side effects including respiratory depression, tolerance/dependence and addiction. The N/OFQ opioid receptor (NOP) also produces analgesia but is devoid of the major MOP side effects. Evidence exists for MOP-NOP interaction and mixed MOP-NOP ligands produce analgesia with reduced side effects. We have generated a HEKMOP/NOP human expression system and used bivalent MOP-NOP and fluorescent ligands to (i) probe for receptor interaction and (ii) consequences of that interaction. We used HEKMOP/NOP cells and two bivalent ligands; Dermorphin-N/OFQ (MOP agonist-NOP agonist; DeNO) and Dermorphin-UFP101 (MOP agonist-NOP antagonist; De101). We have determined receptor binding profiles, GTPγ[35S] binding, cAMP formation and ERK1/2 activation. We have also probed MOP and NOP receptor interactions in HEK cells and hippocampal neurones using the novel MOP fluorescent ligand, DermorphinATTO488 and the NOP fluorescent ligand N/OFQATTO594. In HEKMOP/NOP MOP ligands displaced NOP binding and NOP ligands displaced MOP binding. Using fluorescent probes in HEKMOP/NOP cells we demonstrated MOP-NOP probe overlap and a FRET signal indicating co-localisation. MOP-NOP were also co-localised in hippocampal tissue. In GTPγ[35S] and cAMP assays NOP stimulation shifted the response to MOP rightwards. At ERK1/2 the response to bivalent ligands generally peaked later. We provide evidence for MOP-NOP interaction in recombinant and native tissue. NOP activation reduces responsiveness of MOP activation; this was shown with conventional and bivalent ligands.