PT  - JOURNAL ARTICLE
AU  - Banes, A.
AU  - Florian, J. A.
AU  - Watts, S. W.
TI  - Mechanisms of 5-Hydroxytryptamine<sub>2A</sub> Receptor Activation of the Mitogen-Activated Protein Kinase Pathway in Vascular Smooth Muscle
DP  - 1999 Dec 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1179--1187
VI  - 291
IP  - 3
4099  - http://jpet.aspetjournals.org/content/291/3/1179.short
4100  - http://jpet.aspetjournals.org/content/291/3/1179.full
SO  - J Pharmacol Exp Ther1999 Dec 01; 291
AB  - 5-Hydroxytryptamine (5-HT) activates the extracellular signal-regulated kinase (Erk) mitogen-activated protein kinases (MAPKs) in the vasculature, resulting in contraction. The mechanisms by which this occurs are unclear. G protein-coupled receptors can activate Erk MAPK pathways through a variety of mechanisms, including stimulation of Src, phosphoinositide-3 kinase (PI-3-K), protein kinase C (PKC), or the epidermal growth factor (EGF) receptor tyrosine kinase. We hypothesize that 5-HT uses one or more of these pathways. In isolated strips of rat aorta, the MAPK/Erk kinase inhibitor U0126 (50 μM), Src inhibitor PP1 (0.5 μM), PKC inhibitors calphostin C (1 μM) and chelerythrine (10 μM), and the PI-3-K inhibitor LY294002 (1–20 μM) reduced 5-HT-induced contraction. The EGF receptor tyrosine kinase inhibitor AG1478 (0.25–1 μM) was without effect. Thus, 5-HT activates PKC, Src, and possibly PI-3-K to result in contraction. In rat aortic myocytes, 5-HT (1 μM) activated Erk MAPK proteins 2- to 3-fold over basal values; activation was reduced by U0126, PP1, and LY294002 and unaffected by calphostin C or chelerythrine, wortmannin, or AG1478. The lack of effect of EGF receptor tyrosine kinase and PI-3-K inhibitors was confirmed in that the EGF receptor immunoprecipitated from 5-HT-exposed cells did not display an increase in autophosphorylation, nor did 5-HT significantly increase activation of Akt/protein kinase B, a downstream substrate for PI-3-K. These data suggest that the rat aortic 5-HT2A receptor uses Src but not PKC, PI-3-K, or the EGF receptor tyrosine kinase in stimulating Erk MAPK activation. The American Society for Pharmacology and Experimental Therapeutics