Alterations in 5-HT2A receptor signaling in male and female transgenic rats over-expressing either Gq or RGS-insensitive Gq protein.
Serotonin 2A (5-HT2A) receptors are coupled to Galphaq and Galpha11 proteins to activate phospholipase C (PLC). Regulators of G-protein signaling proteins (RGS) modulate G-protein signaling by accelerating the intrinsic GTPase activity of Galphaq and Galpha11. This study investigated the effects of over-expression of wild-type Galphaq proteins (Gq-Tg) and over-expression of RGS-insensitive Galphaq proteins (G188S, RGSi-Tg) on 5-HT2A receptor mediated signaling in transgenic rats. Over-expression of wild-type Galphaq and RGS insensitive mutant Galphaq did not produce significant alterations in the levels of Galpha11, RGS2, RGS4, RGS7, RGS16 or 5-HT2A proteins. RGSi-Tg rats had higher oxytocin and corticosterone responses to (-)DOI, a 5-HT2A/2C receptor agonist, compared to Gq-Tg rats. RGSi-Tg and Gq-Tg rats had higher ACTH responses to (-)DOI compared to control rats. Similarly, 5-HT-stimulated PLC activity in the frontal cortex was higher in RGSi-Tg and Gq-Tg rats compared to control rats. In contrast, GTPgammaS-stimulated PLC activity was higher in Gq-Tg rats but not in RGSi-Tg rats compared to control rats. There was a small but statistically significant increase in the affinity of [125I]-DOI labeled 5-HT2A receptors in RGSi-Tg rats and Gq-Tg rats compared to controls. There were no significant differences in Bmax and Kd of [3H] ketanserin labeled 5-HT2A receptors among the three groups. These data suggest that the effect of RGS proteins on 5-HT2A receptor signaling is cell type specific. In transgenic rats over-expressing Galphaq, endogenous RGS proteins have a negative effect on 5-HT2A receptor-mediated oxytocin release. In contrast, endogenous RGS protein had no impact on 5-HT2A receptor-mediated ACTH release in transgenic rats.
Shi
Ju
J
Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153, USA.
Damjanoska
Katerina J
KJ
Zemaitaitis
Bozena
B
Garcia
Francisca
F
Carrasco
Gonzalo
G
Sullivan
Nicole R
NR
She
Yijin
Y
Young
Kathleen H
KH
Battaglia
George
G
Van De kar
Louis D
LD
Howland
David S
DS
Muma
Nancy A
NA
D000662:Amphetamines / Q000493:pharmacokinetics; D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D015153:Blotting, Western / Q000379:methods; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism*; D006728:Hormones / Q000097:blood; D017403:In Situ Hybridization / Q000379:methods; D007554:Isotopes / Q000493:pharmacokinetics; D007650:Ketanserin / Q000493:pharmacokinetics; D008297:Male; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D011863:Radioimmunoassay / Q000379:methods; D011869:Radioligand Assay / Q000379:methods; D051381:Rats; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000493:pharmacokinetics; D017366:Serotonin Receptor Agonists / Q000493:pharmacokinetics; D012727:Sex Characteristics; D015398:Signal Transduction / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism
D000662:Amphetamines; D006728:Hormones; D007554:Isotopes; D050505:Mutant Proteins; D020710:RGS Proteins; D044402:Receptor, Serotonin, 5-HT2A; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D007650:Ketanserin; D010738:Type C Phospholipases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine