PT  - JOURNAL ARTICLE
AU  - Rousell, Jonathan
AU  - Haddad, El-Bdaoui
AU  - Lindsay, Mark A.
AU  - Barnes, Peter J.
TI  - Regulation of m2 Muscarinic Receptor Gene Expression by Platelet-Derived Growth Factor: Involvement of Extracellular Signal-Regulated Protein Kinases in the Down-Regulation Process
AID  - 10.1124/mol.52.6.966
DP  - 1997 Dec 01
TA  - Molecular Pharmacology
PG  - 966--973
VI  - 52
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/52/6/966.short
4100  - http://molpharm.aspetjournals.org/content/52/6/966.full
SO  - Mol Pharmacol1997 Dec 01; 52
AB  - To study the role of mitogen-activated protein kinase in the regulation of M2 receptors, we studied the effect of platelet-derived growth factor (PDGF) on M2 receptor gene expression. PDGF (4 ng/ml) caused a time-dependent decrease in M2 receptor number and in m2 receptor mRNA levels in HEL 299 cells. The PDGF-induced loss in m2 mRNA required de novo protein synthesis and occurred through a decrease in the rate of transcription of the m2 receptor gene. The down-regulation of M2receptors was not accompanied by an uncoupling of the remaining receptors, indicating a large receptor reserve in these cells. Preincubations with the phosphatidylinositol 3-kinase inhibitor wortmannin, the protein kinase C inhibitor GF 109203X and the cAMP-dependent protein kinase inhibitor H-8 did not attenuate PDGF-induced down-regulation, indicating a lack of involvement of these enzymes in the down-regulation process. Activation of the extracellular signal-regulated protein kinase (ERK) 1 and 2 proteins was measured by an “in gel” phosphorylation assay. Carbachol did not activate ERK1 or 2, whereas PDGF and 4β-phorbol 13,14-dibutyrate resulted in a large increase in ERK1 and 2 activity along with a decrease in m2 mRNA. Preincubation with PD 098059, an inhibitor of mitogen-activated protein kinase kinase, inhibited PDGF- and 4β-phorbol 13,14-dibutyrate-mediated activation of ERK 1 and 2 in a concentration-dependent manner. The inhibitory action of PD 098059 was reflected at the mRNA level attenuating both PDGF- and 4β-phorbol 13,14-dibutyrate-mediated decreases in m2 mRNA. These results suggest a role of ERK1 and 2 in the regulation of muscarinic m2 receptor gene expression.