Heterodimerization of opioid receptor‐like 1 and µ‐opioid receptors impairs the potency of µ receptor agonist

Abstract

Nociceptin activation of ORL1 (opioid receptor-like 1 receptor) has been shown to antagonize l receptor-mediated analgesia at the supraspinal level. ORL1 and l-opioid receptor (lR) are co-expressed in several subpopulations of CNS neurons involved in regulating pain transmission. The amino acid sequence of ORL1 also shares a high degree of homology with that of l receptor. Thus, it is hypothesized that ORL1 and lR interact to form the heterodimer and that ORL1/lR heterodimerization may be one molecular basis for ORL1-mediated antiopioid effects in the brain. To test this hypothesis, myc-tagged ORL1 and HA-tagged lR are co-expressed in human embryonic kidney (HEK) Grisel et al. 1996;Mogil et al. 1996;Calo et al. 1998;Wang et al. 1999). It has also been reported that intracerebroventricular administration of [Nphe 1 ]nociceptin(1-13)NH2, a selective ORL1 antagonist, potentiates l receptor agonist-induced analgesia and produces a naloxone-resistant antinociceptive effect (Calo et al. 2000a). These results suggest that the functional antagonism of l receptor-mediated analgesia by ORL1 is tonically active at the supraspinal level.A growing number of biochemical, biophysical and functional investigations demonstrated that heterodimerization of distinct G protein-coupled receptors occurs in the plasma membrane and that pharmacological and signaling Received April 20, 2004; revised manuscript received August 13, 2004; accepted October 6, 2004. Address correspondence and reprint requests to Hung-Li Wang, Department of Physiology, Chang Gung University School of Medicine, Kwei-San, Tao-Yuan, Taiwan. E-mail: hlwns@mail.cgu.edu.twAbbreviations used: AT1-R, type 1 angiotensin II receptor; B2-R, type 2 bradykinin receptor; CHO, Chinese hamster ovary; DA, dopamine; DAMGO, [D-Ala 2 ,N-methyl-Phe 4 ,Gly-ol 5 ]enkephalin; GRK2, G proteincoupled receptor kinase 2; HEK, human embryonic kidney; MAPK, mitogen-activated protein kinase; lR, l-opioid receptor; ORL1, opioid receptor-like 1 receptor; PAG, periaqueductal gray; PBS, phosphatebuffered saline; SDS-PAGE, sodium dodecyl sulphate polyacrylamide gel electrophoresis.

Gi/o-Coupled Receptors Compete for Signaling to Adenylyl Cyclase in SH-SY5Y Cells and Reduce Opioid-Mediated cAMP Overshoot

“…Second, there could be complexes of multiple receptors isolated with signaling molecules. Most of the G i/o -coupled receptors expressed in SH-SY5Y cells have been reported to heterodimerize with MOR, including DOR (George et al, 2000;Gomes et al, 2004), NOPr (Wang et al, 2005), ␣ 2 AR (Jordan et al, 2003), and CB 1 (Rios et al, 2006), whereas DOR has been shown to form heterodimers with ␣ 2 AR (Rios et al, 2004). In addition, preformed signaling complexes containing GPCR and multiple effectors have been identified (Davare et al, 2001).…”

“…It has been suggested that the probability of opioid receptor/G protein interaction is enhanced by compartmentalization in the membrane (Alt et al, 2001), allowing rapidity of GPCR signal propagation (Hur and Kim, 2002). Various modes of organization in the plasma membrane have been proposed to describe these compartments, including dimerization of receptors (George et al, 2000;Jordan et al, 2003;Gomes et al, 2004;Rios et al, 2004Rios et al, , 2006Wang et al, 2005), membrane microdomains (Allen et al, 2007), or protein scaffolds (Hall and Lefkowitz, 2002). However, mathematical modeling of experimental findings supporting compartmentalization has claimed that these data can be explained by a collision coupling model (Tolkovsky and Levitzki, 1978;Stickle and Barber, 1992) without the need to invoke compartments (Brinkerhoff et al, 2008).…”

Cellular Mechanisms of Nociceptin/Orphanin FQ (N/OFQ) Peptide (NOP) Receptor Regulation and Heterologous Regulation by N/OFQ

“…However, mechanisms of N/OFQ-mediated MOR desensitization also are cell, time, and signal pathway specific. Short-term N/OFQ pretreatment reduced the ability of the MOR agonists DAMGO (Mandyam et al, 2002;Wang et al, 2005) and morphine (Mandyam et al, 2000) to inhibit cAMP and to stimulate mitogen-activated protein kinase (Hawes et al, 1998). Acute desensitization of MOR responses by N/OFQ in BE(2)-C cells involves translocation of PKCa, GRK2, and GRK3 to the plasma membrane.…”

“…Therefore, acute exposure to N/OFQ enhanced MOR-mediated homologous desensitization in BE(2)-C human neuroblastoma cells. The mechanism(s) by which acute N/OFQ-desensitized MOR responses in CHO and HEK cells were not investigated (Hawes et al, 1998;Wang et al, 2005).…”

Nociceptin/Orphanin FQ Receptor Structure, Signaling, Ligands, Functions, and Interactions with Opioid Systems

“…Heterodimerization can potentially play a role in the modulation of NOP or mu receptor activity by altering receptor-ligand interactions, functional activity of the respective receptors, and receptor trafficking. NOP/mu receptor heterodimers have been demonstrated using coimmunoprecipitation (Pan et al, 2002;Wang et al, 2005;Evans et al, 2010) and immunofluorescence microscopy approaches (Evans et al, 2010). Pan et al (2002) reported a very large (250 fold) increase in the affinity of mu agonists, but not naloxone, for the inhibition of [ 3 H]N/OFQ binding in cells transfected with both receptors.…”