Agonist induced-phosphorylation of Gα11 protein reduces coupling to 5-HT2A receptors

Ju Shi, Katerina J. Damjanoska, Rakesh K. Singh, Gonzalo A. Carrasco, Francisca Garcia, Angela J. Grippo, Michelle Landry, Nicole R. Sullivan, George Battaglia, Nancy A. Muma

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

We previously demonstrated that 24-h treatment with (-)-1-(2,5-dimethoxy-4- iodophenyl)-2-aminopropane HCl (DOI) causes phosphorylation of G α11 protein at serine 154 and that this phosphorylation causes desensitization of serotonin (5-HT) 2A receptor signaling in A1A1v cells (Shi et al., 2007). We now report that treatment of A1A1v cells with DOI for 24 h produces a greater reduction in the Bmax of [125I] (±)-DOI-labeled high-affinity binding sites (46%) than the reduction of [3H]ketanserin binding sites (25%). Although the KD values are not altered, there is a smaller amount of GTPγS [guanosine 5′-3-O-(thio)-triphosphate]-sensitive [125I](±)-DOI binding in DOI-treated cells. These results suggest that DOI treatment causes downregulation of 5-HT2A receptors and reductions in G protein-coupled 5-HT2A receptors. In contrast, in cells transfected with the phosphorylation state mimic Gα11S154D, GTPγS-sensitive [125I](±)-DOI binding was decreased by 48%; however, there was no significant difference in the KD and Bmax values of [125I](±)-DOI-labeled receptors. The receptor binding experiments suggest that phosphorylation of G α11 on serine 154 reduces coupling of 5-HT2A receptors, whereas DOI causes down-regulation of 5-HT2A receptors in addition to the phosphorylation-induced uncoupling of Gα11 to 5-HT2A receptors. To determine whether DOI increases phosphorylation of Gαq/11 protein in vivo, rats were treated with 1 mg/kg/day DOI or saline for 1 to 7 days. Seven days of DOI treatment significantly decreased phospholipase C activity stimulated by an Emax concentration of 5-HT by 40% and increased phosphorylation of G αq/11 proteins by 51% in the frontal cortex. These data suggest that DOI causes phosphorylation of Gαq/11 in vivo and could thereby contribute to the desensitization of 5-HT2A receptors.

Original languageEnglish (US)
Pages (from-to)248-256
Number of pages9
JournalJournal of Pharmacology and Experimental Therapeutics
Volume323
Issue number1
DOIs
StatePublished - Oct 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Pharmacology

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