δ-Opioid Receptors Stimulate the Metabolic Sensor AMP-Activated Protein Kinase through Coincident Signaling with G_q/11-Coupled Receptors

Abstract

AMP-activated protein kinase (AMPK) and ␦-opioid receptors (DORs) are both involved in controlling cell survival, energy metabolism, and food intake, but little is known on the interaction between these two signaling molecules. Here we show that activation of human DORs stably expressed in Chinese hamster ovary (CHO) cells increased AMPK activity and AMPK phosphorylation on Thr172. DOR-induced AMPK phosphorylation was prevented by pertussis toxin, reduced by protein kinase A (PKA) activators, and unaffected by PKA, transforming growth factor-␤-activated kinase 1, mitogen-activated protein kinase, and protein kinase C inhibitors. Conversely, the DOR effect was reduced by Ca 2ϩ / calmodulin-dependent protein kinase kinase (CaMKK) inhibition, apyrase treatment, G q/11 antagonism, and blockade of P2 purinergic receptors. Apyrase treatment also depressed DOR stimulation of intracellular Ca 2ϩ concentration, whereas P2 receptor antagonism blocked DOR stimulation of inositol phosphate accumulation. In SH-SY5Y neuroblastoma cells and primary olfactory bulb neurons, DOR activation failed to affect AMPK phosphorylation per se but potentiated the stimulation by either muscarinic agonists or 2-methyl-thio-ADP. Sequestration of G protein ␤␥ subunits (G␤␥) blocked the DOR potentiation of AMPK phosphorylation induced by oxotremorine-M. In CHO cells, the AMPK activator 5-aminoimidazole-4-carboxamide1-␤-D-ribonucleoside stimulated AMPK phosphorylation and glucose uptake, whereas pharmacological inhibition of AMPK, expression of a dominantnegative mutant of AMPK␣1, and P2Y receptor blockade reduced DOR-stimulated glucose uptake. The data indicate that in different cell systems, DOR activation up-regulates AMPK through a G␤␥-dependent synergistic interaction with G q/11 -coupled receptors, potentiating Ca 2ϩ release and CaMKK␤-dependent AMPK phosphorylation. In CHO cells, this coincident signaling mechanism is involved in DOR-induced glucose uptake.

Molecular Pharmacology ofδ-Opioid Receptors

“…In contrast with predominantly inhibitory responses evoked by striatal DOPr, stimulation of those present in the olfactory bulbs (Onali and Olianas, 2004), medial prefrontal cortex (Olianas et al, 2012), and primary cultures of hippocampal neurons (Yao et al, 2003) potentiate cAMP production by Gas-coupled receptors. This opposing modulation of cAMP levels by striatal and hippocampal receptors is consistent with divergent effects of DOPr silencing upon behaviors controlled by these structures.…”

“…Endogenously expressed DOPrs in primary olfactory neurons also activate glucose uptake via AMPK, suggesting the involvement of this pathway in neuronal metabolism. In this cellular background, AMPK activation by DOPr involved Gbg, Ca +2 mobilization, and calmodulin-dependent protein kinase kinase activity, whereas an increase in glucose uptake also required activation of Gaq (Olianas et al, 2012).…”

“…In CHO cells, AMPK is required for DOPr-stimulated Akt activity (Olianas et al, 2011) and DOPr-induced glucose uptake (Olianas et al, 2012). Endogenously expressed DOPrs in primary olfactory neurons also activate glucose uptake via AMPK, suggesting the involvement of this pathway in neuronal metabolism.…”

Alpinetin activates the δ receptor instead of the κ and μ receptor pathways to protect against rat myocardial cell apoptosis

“…As demonstrated by previous studies, the δ receptor functions via the G-protein and KATP channel signal transduction pathways (36,37) and is closely associated with PKC (38). PKC is a member of the serine/threonine kinase family and exhibits extensive biological activities, including regulating the proliferation and differentiation of numerous cell types (39–41).…”

Melatonin regulates the transcription of βAPP‐cleaving secretases mediated through melatonin receptors in human neuroblastoma SH‐SY5Y cells

“…After reaching 90% confluence, cells were treated with various concentrations of PKC activator, PDBu (0.1, 1, 10, and 100 μ m ), in complete medium for 2 hr . In some experiment, cells were pretreated with 1 μ m Go 6983, PKC inhibitor, for 30 min prior to 1 μ m melatonin administration for 24 hr. After that, ADAM10 levels were measured by Western blot analysis.…”