RT Journal Article SR Electronic T1 Cannabinoid Tolerance in S426A/S430A x β-Arrestin 2 Knockout Double-Mutant Mice JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 17 OP 34 DO 10.1124/jpet.122.001367 VO 385 IS 1 A1 Mary K. Piscura A1 Diana E. Sepulveda A1 Malabika Maulik A1 Josée Guindon A1 Angela N. Henderson-Redmond A1 Daniel J. Morgan YR 2023 UL http://jpet.aspetjournals.org/content/385/1/17.abstract AB Tolerance to compounds that target G protein–coupled receptors (GPCRs), such as the cannabinoid type-1 receptor (CB1R), is in part facilitated by receptor desensitization. Processes that mediate CB1R desensitization include phosphorylation of CB1R residues S426 and S430 by a GPCR kinase and subsequent recruitment of the β-arrestin2 scaffolding protein. Tolerance to cannabinoid drugs is reduced in S426A/S430A mutant mice and β-arrestin2 knockout (KO) mice according to previous work in vivo. However, the presence of additional phosphorylatable residues on the CB1R C-terminus made it unclear as to whether recruitment to S426 and S430 accounted for all desensitization and tolerance by β-arrestin2. Therefore, we assessed acute response and tolerance to the cannabinoids delta-9-tetrahydrocannabinol (Δ9-THC) and CP55,940 in S426A/S430A x β-arrestin2 KO double-mutant mice. We observed both delayed tolerance and increased sensitivity to the antinociceptive and hypothermic effects of CP55,940 in male S426A/S430A single- and double-mutant mice compared with wild-type littermates, but not with Δ9-THC. Female S426A/S430A single- and double-mutant mice were more sensitive to acute antinociception (CP55,940 and Δ9-THC) and hypothermia (CP55,940 only) exclusively after chronic dosing and did not differ in the development of tolerance. These results indicate that phosphorylation of S426 and S430 are likely responsible for β-arrestin2–mediated desensitization as double-mutant mice did not differ from the S426A/S430A single-mutant model in respect to cannabinoid tolerance and sensitivity. We also found antinociceptive and hypothermic effects from cannabinoid treatment demonstrated by sex-, agonist-, and duration-dependent features.SIGNIFICANCE STATEMENT A better understanding of the molecular mechanisms involved in tolerance will improve the therapeutic potential of cannabinoid drugs. This study determined that further deletion of β-arrestin2 does not enhance the delay in cannabinoid tolerance observed in CB1R S426A/S430A mutant mice.