Stimulation of the calcitonin gene-related peptide enhancer by mitogen-activated protein kinases and repression by an antimigraine drug in trigeminal ganglia neurons.
Calcitonin gene-related peptide (CGRP) is involved in the underlying pathophysiology of all vascular headaches, including migraines. Elevated levels of CGRP during migraine are restored to normal coincident with headache relief after treatment with the antimigraine drug sumatriptan. We have used primary cultures of trigeminal neurons under conditions simulating migraine pathology and therapy to study the mechanisms controlling the CGRP promoter. Using reporter genes in transient transfection assays, we demonstrate that an 18 bp enhancer containing a helix-loop-helix element is both necessary and sufficient for full promoter activity. NGF treatment and cotransfection with an upstream activator of the extracellular signal-regulated MAP kinases (MAPKs) activated the enhancer. Treatment with sumatriptan repressed NGF- and MAPK-stimulated CGRP promoter activity. Repression was also observed using a synthetic MAPK-responsive reporter gene. Sumatriptan regulation of CGRP gene expression did not couple to a G(i)/G(o) pathway, but rather caused a prolonged increase in intracellular calcium. The importance of the prolonged calcium signal in repression of MAPK activity was demonstrated by using the ionophore ionomycin to mimic sumatriptan action. We propose that activation of MAPK pathways may increase CGRP gene expression during migraine, and that sumatriptan can diametrically oppose that activation via a prolonged elevation of intracellular calcium.
Durham
Paul L
PL
Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, USA. pauldurham@smsu.edu
Russo
Andrew F
AF
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004742:Enhancer Elements, Genetic / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D019077:Helix-Turn-Helix Motifs / Q000502:physiology; D007424:Intracellular Fluid / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D008881:Migraine Disorders / Q000503:physiopathology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism* / Q000494:pharmacology; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018170:Sumatriptan / Q000494:pharmacology*; D014162:Transfection; D012668:Trigeminal Ganglion / Q000166:cytology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D007476:Ionophores; D014662:Vasoconstrictor Agents; D018170:Sumatriptan; D020932:Nerve Growth Factor; D037342:Pertussis Toxin; D020928:Mitogen-Activated Protein Kinases; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium