title: Differential regulation of mitogen-activated protein kinase-responsive genes by the duration of a calcium signal.
abstract: We have investigated the cellular mechanisms by which changes in intracellular calcium (Ca2+) can differentially regulate gene expression. Two Ca2+ paradigms, involving prolonged and transient Ca2+ increases, were used. As a starting point, we studied the slow, prolonged elevation of Ca2+ caused by activation of 5-HT1 receptors. We had previously shown that 5-HT1 agonists inhibit calcitonin gene-related peptide (CGRP) transcription and secretion. The Ca2+ ionophore, ionomycin, was used to produce a prolonged elevation of the Ca2+ signal similar to that generated by 5-HT1 receptor agonists. Ionomycin treatment of the neuronal-like CA77 cell line specifically inhibited mitogen-activated protein (MAP) kinase stimulation of the CGRP enhancer and two synthetic MAP kinase-responsive reporter genes (4- to 10-fold). We then showed that ionomycin repression of promoter activity involved selective induction of MAP kinase phosphatase-1 (MKP-1), but not MKP-2, and that overexpression of MKP-1 was sufficient to repress CGRP enhancer activity. These effects were then compared with a Ca2+ paradigm involving a transient elevation in Ca2+ as seen after depolarization. At 4 h after the transient increase in Ca2+, the CGRP enhancer and synthetic MAP kinase-responsive reporter genes were stimulated. In contrast, exposure to depolarizing stimuli overnight caused only a less than 2-fold inhibition of promoter activity. We propose that the duration of the Ca2+ signal can determine the magnitude of a negative feedback loop that leads to differential regulation of MAP kinase-responsive genes.
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: D015740:Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D018797:Cell Cycle Proteins; D002460:Cell Line; D054638:Dual Specificity Phosphatase 1; D004742:Enhancer Elements, Genetic; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter / Q000187:drug effects; D017874:Immediate-Early Proteins / Q000096:biosynthesis; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis; D011985:Receptors, Serotonin / Q000502:physiology; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013961:Thyroid Gland; D013997:Time Factors
chemical_list: D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D007476:Ionophores; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D015759:Ionomycin; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium