PMID:19172190

Citation	Wang, HY and Burns, LH (2009) Naloxone's pentapeptide binding site on filamin A blocks Mu opioid receptor-Gs coupling and CREB activation of acute morphine. PLoS ONE 4:e4282
Abstract	Chronic morphine causes the mu opioid receptor (MOR) to switch its coupling from Gi/o to Gs, resulting in excitatory signaling via both Galphas and its Gbetagamma dimer. Ultra-low-dose naloxone (NLX) prevents this switch and attenuates opioid tolerance and dependence. This protective effect is mediated via a high-affinity interaction of NLX to a pentapeptide region in c-terminal filamin A (FLNA), a scaffolding protein interacting with MOR. In organotypic striatal slice cultures, we now show that acute morphine induces a dose-dependent Go-to-Gs coupling switch at 5 and 15 min that resolves by 1 hr. The acute Gs coupling induced by 100 microM morphine was completely prevented by co-treatment with 100 pM NLX, (+)NLX, or naltrexone (NTX), or their pentapeptide binding site (FLNA(2561-2565)), which we show can act as a decoy for MOR or bind to FLNA itself. All of these co-treatments presumably prevent the MOR-FLNA interaction. Since ultra-low-dose NTX also attenuates the addictive properties of opioids, we assessed striatal cAMP production and CREB phosphorylation at S(133). Correlating with the Gs coupling, acute morphine induced elevated cAMP levels and a several-fold increase in pS(133)CREB that were also completely blocked by NLX, NTX or the FLNA pentapeptide. We propose that acute, robust stimulation of MOR causes an interaction with FLNA that allows an initially transient MOR-Gs coupling, which recovers with receptor recycling but persists when MOR stimulation is repeated or prolonged. The complete prevention of this acute, morphine-induced MOR-Gs coupling by 100 pM NLX/NTX or 10 microM pentapeptide segment of FLNA further elucidates both MOR signaling and the mechanism of action of ultra-low-dose NLX or NTX in attenuating opioid tolerance, dependence and addictive potential.
Links	PubMed PMC2628740 Online version:10.1371/journal.pone.0004282
Keywords	Analgesics, Opioid/metabolism; Animals; Binding Sites; Brain/metabolism; Contractile Proteins/chemistry; Cyclic AMP Response Element-Binding Protein/metabolism; Filamins; Male; Microfilament Proteins/chemistry; Morphine/pharmacology; Naloxone/chemistry; Naloxone/pharmacology; Narcotic Antagonists/chemistry; Narcotic Antagonists/pharmacology; Peptides/chemistry; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled/metabolism; Receptors, Opioid, mu/metabolism; Signal Transduction
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RAT:OPRM	enables	GO:0031005: filamin binding	ECO:0000315: mutant phenotype evidence used in manual assertion		F		Seeded From UniProt	complete
RAT:OPRM	involved_in	GO:0038003: opioid receptor signaling pathway	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
RAT:OPRM	enables	GO:0038047: morphine receptor activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete

References

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