Ras Involvement in Signal Transduction by the Serotonin 5-HT2B Receptor

doi:10.1074/jbc.271.6.3141

Ras Involvement in Signal Transduction by the Serotonin 5-HT2B Receptor (*)

From the (1)Institut de Génétique et de Biologie Moléculaire et Cellulaire, Université L. Pasteur de Strasbourg, CNRS, INSERM, BP 163-67404 Illkirch Cedex, France,
(2)Différenciation Cellulaire, Unité de Recherche Associée 1960 CNRS, Institut Pasteur, 75724 Paris Cedex 15 France, and
(3)Formation de Recherche Associée C. Bernard, Neurochimie des Communications Cellulaires, Service de Biochimie Hôpital Lariboisière, and Laboratoire de Biologie Cellulaire Faculté de Pharmacie rue de l'Observatoire, 75006 Paris, France

^§To whom correspondence should be addressed:
Institut de Génétique et de Biologie Moléculaire et Cellulaire CNRS, INSERM, Université L. Pasteur de Strasbourg BP 163-67404 Illkirch Cedex, France
. Tel: 33-88-65-33-85; Fax: 33-88-65-32-01.

Abstract

The family of serotonin 5-HT2 receptors stimulates the phospholipase C second messenger pathway via the α subunit of the G GTP-binding protein. Here, we show that agonist stimulation of the 5-HT2B receptor subtype stably expressed in the mouse fibroblast LMTK cell line causes a rapid and transient activation of the proto-oncogene product p21 as measured by an increase in GTP-bound Ras in response to serotonin. Furthermore, 5-HT2B receptor stimulation activates p42/p44 (ERK2/ERK1) mitogen-activated protein kinases as assayed by phosphorylation of myelin basic protein. Antibodies against p21, Gα, -β, or - subunits of the GTP-binding protein inhibit MAP kinase-dependent phosphorylation. The MAP kinase activation is correlated with a stimulation of cell division by serotonin. In addition to this mitogenic action, transforming activity of serotonin is mediated by the 5-HT2B receptor since its expression in LMTK cells is absolutely required for foci formation and for these foci to form tumors in nude mice. Finally, we detected expression of the 5-HT2B receptor in spontaneous human and Mastomys natalensis carcinoid tumors and, similar to the 5-HT2B receptor transfected cells, the Mastomys tumor cells are also responsive to serotonin with similar coupling to p21 activation.

Footnotes

↵* This work was supported by funds from the CNRS, the INSERM, the Centre Hospitalier Universitaire Régional, and by grants from the European Economic Community, the Ministère de l'Enseigement, the Fondation pour la Recherche Médicale, and Association pour la Recherche contre le Cancer Grant 6800 (to D.-S. C. and L. M.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

5-HT

serotonin, 5-hydroxytryptamine

CT

carcinoid tumors

DMEM

Dulbecco's modified Eagle's medium

[I]DOI

(±)-[I]1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl

FCS

fetal calf serum

G-protein

GTP-binding protein

MAP

mitogen-activated protein

MBP

myelin basic protein.
↵²J.-M. Launay, S. Loric, V. Bastide-Douzou, M. Da Prada, and O. Kellermann, submitted for publication.
↵³O. Kellermann, S. Loric, L. Maroteaux, and J.-M. Launay, submitted for publication.
↵⁴J.-M. Launay and L. Maroteaux, unpublished data.
- Received July 6, 1995.
- Revision received December 4, 1995.