(696.1) S426/S430 phosphorylation accounts for Beta-arrestin 2-mediated desensitization for cannabinoid sensitivity and tolerance in mutant mice

Poster Board Number: B72

Mary Piscura (Marshall University), Angela Henderson-Redmond (Marshall University), Diana Sepulveda (Penn State University), Daniel Morgan (Marshall University)

Desensitization of G protein-coupled receptors, such as the cannabinoid receptor 1 (CB1R), is a key mechanism involved in the in the development of tolerance. CB1R desensitization is mediated via phosphorylation of residues S426 and S430 by a G protein-coupled receptor kinase (GRK). Following GRK-mediated phosphorylation at these residues, beta-arrestin 2 (bArr2) is recruited to facilitate desensitization of the receptor. Previous work demonstrated that tolerance for cannabinoid drugs was reduced in S426A/S430A mutant mice and in bArr2-KO mice. Since there are other phosphorylatable serine and threonine residues in the C-terminal tail of CB1R, it was not clear whether bArr2 recruitment to S426 and S430 accounts for all bArr2-mediated desensitization. To address this question, we assessed cannabinoid acute response and daily tolerance in S426A/S430A x bArr2-KO double mutant mice. Both S426A/S430A and bArr2-KO single mutant mice display increased sensitivity and delayed tolerance to the antinociceptive effects of delta-9-tetrahydrocannabinol (Δ9-THC) and the synthetic cannabinoid, CP55,940. Double mutant mice did not differ from the S426A/S430A single mutant model in respect to antinociception, suggesting that the effect of complete bArr2 deletion did not enhance the effect of the S426A/S430A point mutants. However, the hypothermic effects of acute Δ9-THC dosing were increased in male double mutant mice, relative to S426A/S430A and bArr2 single mutant mice. These results indicate that phosphorylation of S426 and S430 are likely responsible for bArr2-mediated desensitization, with the exception of hypothermia induced by acute Δ9-THC dosing. Therefore, these results also suggest sensitivity to cannabinoid-induced hypothermia is agonist- and duration-dependent.

Support or Funding Information

This work was supported by NIH research grant DA044999.

lt;pgt;This work was supported by NIH research grant DA044999.lt;/pgt;