Abstract

We examined the effects of the bronchoconstrictor agonists serotonin (5-hydroxytryptamine; 5-HT) and histamine on mitogen-activated protein (MAP) kinase activation in cultured bovine tracheal myocytes. Kinase renaturation assays demonstrated activation of the 42- and 44-kDa MAP kinases within 2 min of 5-HT exposure. MAP kinase activation was mimicked by alpha-methyl-5-HT and reduced by pretreatment with either phorbol 12,13-dibutyrate or forskolin, suggesting activation of the 5-HT2 receptor, protein kinase C, and Raf-1, respectively. Raf-1 activation was confirmed by measurement of Raf-1 activity, and the requirement of Raf-1 for 5-HT-induced MAP kinase activation was demonstrated by transient transfection of cells with a dominant-negative allele of Raf-1. Histamine pretreatment significantly inhibited 5-HT and insulin-derived growth factor-1-induced MAP kinase activation. Attenuation of MAP kinase activation was reversed by cimetidine, mimicked by forskolin, and accompanied by cAMP accumulation and inhibition of Raf-1, suggesting activation of the H2 receptor and cAMP-dependent protein kinase A. However, histamine treatment inhibited Raf-1 but not MAP kinase activation following treatment with either platelet-derived growth factor or epidermal growth factor, implying a Raf-1-independent MAP kinase activation pathway. In summary, our data suggest a model whereby 5-HT activates MAP kinase via a protein kinase C/Raf-1 pathway, and histamine attenuates MAP kinase activation by serotonin via activation of cAMP-dependent protein kinase A and inhibition of Raf-1.

Highlights

  • We examined the effects of the bronchoconstrictor agorrists serotonin (5-hydroxytryptamine; 5-HT) and histamine on mitogen-activated protein (MAP) kinase activation in cultured bovine tracheal myocytes

  • We have demonstrated that Caz+ flux activates MAP kinase in human foreskin fibroblasts [30], whereas cAMP accumulation suppresses MAP kinase by dium; MBP, myelin basic protein; MEK, MAP kinaselERK-activating kinase; Pipes, 1,4-piperazinediethanesulfonic acid

  • We have demonstrated that the bronchoconstrictors 5-HT and histamine each influence MAP kinase activation in cultured bovine tracheal smooth muscle cells. 5-HT activates MAP kinase, likely via a protein kinase CIRaf-1 pathway, whereas histamine attenuates MAP kinase activation, apparently via stimulation of cAMP-dependent protein kinase A and inhibition of Raf-l

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Summary

THE JOURNAL OF BIOLOGICAL CHEMISTRY

19908-19913, 1995 Printed in U.S.A. Histamine Antagonizes Serotonin and Growth Factor-induced Mitogen-activated Protein Kinase Activation in Bovine Tracheal Smooth Muscle Cells*. We examined the effects of the bronchoconstrictor agorrists serotonin (5-hydroxytryptamine; 5-HT) and histamine on mitogen-activated protein (MAP) kinase activation in cultured bovine tracheal myocytes. Our data suggest a model whereby 5-HT activates MAP kinase via a protein kinase ClRaf-l pathway, and histamine attenuates MAP kinase activation by serotonin via activation of cAMP-dependent protein kinase A and inhibition of Raf-l. The net effect of histamine treatment on MAP kinase activation in cultured airway smooth muscle cells may depend on the relative stimulation of the two pathways. Our data suggest a model whereby 5-HT activates MAP kinase via a protein kinase ClRaf-1 pathway, and histamine inhibits MAP kinase activation via stimulation of cAMP-dependent protein kinase A and inhibition of Raf-l

EXPERIMENTAL PROCEDURES
Bronchoconstrictors and MAP Kina se
DISCUSSION
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