Phospholipase C, Ca2+, and calmodulin signaling are required for 5-HT2A receptor-mediated transamidation of Rac1 by transglutaminase

Ying Dai, Nichole L. Dudek, Qian Li, Nancy A. Muma

Research output: Contribution to journalArticlepeer-review

Abstract

Rationale: Serotonin and especially serotonin 2A (5-HT2A) receptor signaling are important in the etiology and treatment of schizophrenia and affective disorders. We previously reported a novel 5-HT2A receptor effector, increased transglutaminase (TGase)-catalyzed transamidation, and activation of the small G protein Rac1 in A1A1v cells, a rat embryonic cortical cell line. Objectives: In this study, we explore the signaling pathway involved in 5-HT2A receptor-mediated Rac1 transamidation. Methods: A1A1v cells were pretreated with pharmacological inhibitors of phospholipase C (PLC) or calmodulin (CaM), and then stimulated by the 5-HT2A receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI). Intracellular Ca2+ concentration and TGase-modified Rac1 transamidation were monitored. The effect of manipulation of intracellular Ca2+ by a Ca2+ ionophore or a chelating agent on Rac1 transamidation was also evaluated. Results: In cells pretreated with a PLC inhibitor U73122, DOI-stimulated increases in the intracellular Ca2+ concentration and TGase-modified Rac1 were significantly attenuated as compared to those pretreated with U73343, an inactive analog. The membrane-permeant Ca2+ chelator, BAPTA-AM strongly reduced TGase-catalyzed Rac1 transamidation upon DOI stimulation. Conversely, the Ca2+ ionophore ionomycin, at a concentration that induced an elevation of cytosolic Ca2+ to a level comparable to cells treated with DOI, produced an increase in TGase-modified Rac1 without 5-HT 2A receptor activation. Moreover, the CaM inhibitor W-7, significantly decreased Rac1 transamidation in a dose-dependent manner in DOI-treated cells. Conclusions: These results indicate that 5-HT2A receptor-coupled PLC activation and subsequent Ca2+ and CaM signaling are necessary for TGase-catalyzed Rac1 transamidation, and an increase in intracellular Ca2+ is sufficient to induce Rac1 transamidation.

Original languageEnglish (US)
Pages (from-to)403-412
Number of pages10
JournalPsychopharmacology
Volume213
Issue number2-3
DOIs
StatePublished - Feb 2011
Externally publishedYes

Keywords

  • 5-HT receptor
  • A1A1v cells
  • Calcium
  • Calmodulin
  • Phospholipase C
  • Rac1
  • Serotonin
  • Serotonylation
  • Small G proteins
  • Transamidation
  • Transglutaminase

ASJC Scopus subject areas

  • Pharmacology

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