title: Serotonergic repression of mitogen-activated protein kinase control of the calcitonin gene-related peptide enhancer.
abstract: We have investigated the mechanisms underlying regulation of the calcitonin gene-related peptide (CGRP) cell-specific enhancer. Recently, we reported that this enhancer is inhibited by serotonin type-1 (5-HT1) agonists, similar to currently used antimigraine drugs. We have now tested whether this repression involves a mitogen-activated protein (MAP) kinase pathway. We first demonstrate that the CGRP enhancer is strongly (10-fold) activated by a constitutively active MAP kinase kinase (MEK1), yielding reporter activities 100-fold above the enhancerless control. The involvement of a MAP kinase pathway was confirmed by down-regulation of reporter activity upon cotransfection of a dominant negative Ras. Activation of the enhancer by MEK1 was blocked in a dose-dependent manner by the 5-HT1 receptor agonist CGS 12066A (CGS). Since it is not known whether the CGRP enhancer factors are immediate targets of MAP kinases, we then used EIk-1- and c-Jun-dependent reporter genes that are directly activated by the ERK (extracellular signal-regulated kinases) and JNK (c-Jun N-terminal kinase) MAP kinases. CGS treatment repressed the activation of both of these reporters, suggesting that at least two MAP kinases are the immediate targets of CGS-mediated repression. We further demonstrate that 5-HT1 agonists inactivate ERK by dephosphorylation, even in the presence of constitutively activated MEK1. This inactivation appears to be due to a marked increase in the level of MAP kinase phosphatase-1. These results have defined a novel and general mechanism by which 5-HT1 receptor agonists can repress MAP kinase activation of target genes, such as CGRP.
authors.affiliation: Department of Physiology and Biophysics, University of Iowa, Iowa City 52242, USA.
authors.forename: P L
authors.initials: PL
authors.lastname: Durham
authors.forename: A F
authors.initials: AF
authors.lastname: Russo
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D018276:Carcinoma, Medullary; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D054638:Dual Specificity Phosphatase 1; D004742:Enhancer Elements, Genetic; D016758:Genes, jun / Q000235:genetics; D017874:Immediate-Early Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics; D054645:Protein Phosphatase 1; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000502:physiology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013964:Thyroid Neoplasms; D014157:Transcription Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D050807:ets-Domain Protein Elk-1
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C494114:Elk1 protein, rat; D017874:Immediate-Early Proteins; D011518:Proto-Oncogene Proteins; D011810:Quinoxalines; D017366:Serotonin Receptor Agonists; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; C052561:CGS 12066B; D012701:Serotonin; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D015740:Calcitonin Gene-Related Peptide