TY - JOUR
T1 - Mutation of putative GRK phosphorylation sites in the cannabinoid receptor 1 (CB1R) confers resistance to cannabinoid tolerance and hypersensitivity to cannabinoids in mice
AU - Morgan, Daniel J.
AU - Davis, Brian J.
AU - Kearn, Chris S.
AU - Marcus, David
AU - Cook, Alex J.
AU - Wager-Miller, Jim
AU - Straiker, Alex
AU - Myoga, Michael H.
AU - Karduck, Jeffrey
AU - Leishman, Emma
AU - Sim-Selley, Laura J.
AU - Czyzyk, Traci A.
AU - Bradshaw, Heather B.
AU - Selley, Dana E.
AU - Mackie, Ken
PY - 2014
Y1 - 2014
N2 - For many G-protein-coupled receptors (GPCRs), including cannabinoid receptor 1 (CB1R), desensitization has been proposed as a principal mechanism driving initial tolerance to agonists. GPCR desensitization typically requires phosphorylation by a G-proteincoupled receptor kinase (GRK) and interaction of the phosphorylated receptor with an arrestin. In simple model systems, CB1R is desensitized by GRK phosphorylation at two serine residues (S426 and S430). However, the role of these serine residues in tolerance and dependence for cannabinoids in vivo was unclear. Therefore, we generated mice where S426 and S430 were mutated to nonphosphorylatable alanines (S426A/S430A). S426A/S430A mutant mice were more sensitive to acutely administered delta-9-tetrahydrocannabinol (Δ9-THC), have delayed tolerance to Δ9-THC, and showed increased dependence for Δ9-THC. S426A/S430A mutants also showed increased responses to elevated levels of endogenous cannabinoids. CB1R desensitization in the periaqueductal gray and spinal cord following7dof treatment with Δ9-THC was absent in S426A/S430A mutants. Δ9-THC-induced downregulation of CB1Rin the spinal cord was also absent in S426A/S430A mutants. Cultured autaptic hippocampal neurons from S426A/S430A mice showed enhanced endocannabinoid-mediated depolarization-induced suppression of excitation (DSE) and reduced agonist-mediated desensitization of DSE. These results indicate that S426 and S430 play major roles in the acute response to, tolerance to, and dependence on cannabinoids. Additionally, S426A/S430A mice are a novel model for studying pathophysiological processes thought to involve excessive endocannabinoid signaling such as drug addiction and metabolic disease. These mice also validate the approach of mutating GRK phosphorylation sites involved in desensitization as a general means to confer exaggerated signaling to GPCRs in vivo.
AB - For many G-protein-coupled receptors (GPCRs), including cannabinoid receptor 1 (CB1R), desensitization has been proposed as a principal mechanism driving initial tolerance to agonists. GPCR desensitization typically requires phosphorylation by a G-proteincoupled receptor kinase (GRK) and interaction of the phosphorylated receptor with an arrestin. In simple model systems, CB1R is desensitized by GRK phosphorylation at two serine residues (S426 and S430). However, the role of these serine residues in tolerance and dependence for cannabinoids in vivo was unclear. Therefore, we generated mice where S426 and S430 were mutated to nonphosphorylatable alanines (S426A/S430A). S426A/S430A mutant mice were more sensitive to acutely administered delta-9-tetrahydrocannabinol (Δ9-THC), have delayed tolerance to Δ9-THC, and showed increased dependence for Δ9-THC. S426A/S430A mutants also showed increased responses to elevated levels of endogenous cannabinoids. CB1R desensitization in the periaqueductal gray and spinal cord following7dof treatment with Δ9-THC was absent in S426A/S430A mutants. Δ9-THC-induced downregulation of CB1Rin the spinal cord was also absent in S426A/S430A mutants. Cultured autaptic hippocampal neurons from S426A/S430A mice showed enhanced endocannabinoid-mediated depolarization-induced suppression of excitation (DSE) and reduced agonist-mediated desensitization of DSE. These results indicate that S426 and S430 play major roles in the acute response to, tolerance to, and dependence on cannabinoids. Additionally, S426A/S430A mice are a novel model for studying pathophysiological processes thought to involve excessive endocannabinoid signaling such as drug addiction and metabolic disease. These mice also validate the approach of mutating GRK phosphorylation sites involved in desensitization as a general means to confer exaggerated signaling to GPCRs in vivo.
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U2 - 10.1523/JNEUROSCI.3445-12.2014
DO - 10.1523/JNEUROSCI.3445-12.2014
M3 - Article
C2 - 24719095
AN - SCOPUS:84899489705
SN - 0270-6474
VL - 34
SP - 5152
EP - 5163
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 15
ER -