Platelet-derived growth factor activates a mammalian Ste20 coupled mitogen-activated protein kinase in airway smooth muscle.
We have investigated the mechanisms regulating p38MAPK in airway smooth muscle cells. Incubation of cells with platelet-derived growth factor (PDGF) stimulated MAPKA kinase-2 activity, a kinase immediately down-stream of P38MAPK. Preincubation of the cells with forskolin (10 microM), which stimulated a 20-fold increase in intracellular cAMP formation, inhibited this response. An antibody raised against subdomain VI of yeast Ste20 kinase co-immunoprecipitated p38MAPK from cell lysates. The immunoprecipitated kinase(s) was shown to catalyse the phosphorylation of myelin basic protein (MBP) and to activate purified MAPKAP kinase-2. Incubation of cells with PDGF did not increase the amount of p38MAPK isolated in the anti-Ste20 immunoprecipitate. However, the kinase phosphorylated MBP and stimulated purified MAPKAP kinase-2 activity more effectively than kinase from control cells. The preincubation of cells with forskolin (10 microM) reduced the amount of P38MAPK in the immunoprecipitate and this correlated with a decrease in kinase activity. We conclude the PDGF induces the activation of p38MAPK, whereas forskolin elicits its dissociation from the complex with Ste20. Therefore, Ste20/p38MAPK may form part of a signal transduction pathway linked to activation of MAPKAP kinase-2 in ASM cells.
Pyne
N J
NJ
Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, Scotland.
Pyne
S
S
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006168:Guinea Pigs; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011817:Rabbits; D029701:Saccharomyces cerevisiae Proteins; D014443:Tyrosine / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010982:Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D029701:Saccharomyces cerevisiae Proteins; D014443:Tyrosine; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C078754:STE20 protein, S cerevisiae