Feedback regulation of Raf-1 and mitogen-activated protein kinase (MAP) kinase kinases 1 and 2 by MAP kinase phosphatase-1 (MKP-1).
Inactivation of growth factor-regulated mitogen-activated protein (MAP) kinases (ERK1 and ERK2) has been proposed to occur in part through dephosphorylation by the dual specificity MAP kinase phosphatase-1 (MKP-1), an immediate early gene that is induced by mitogenic signaling. In this study, we examined the effect of MKP-1 on signaling components upstream of ERK1 and ERK2. Coexpression of MKK1 or MKK2 with MKP-1 resulted in 7-10-fold activation of mitogen-activated protein kinase kinase (MKK), which required the presence of regulatory serine phosphorylation sites. Endogenous MKK1 and MKK2 were also activated upon MKP-1 expression. Raf-1, a direct regulator of MKK1 and MKK2, was activated under these conditions, and a synergistic activation of MKK was observed upon coexpression of Raf-1 and MKP-1. This effect did not appear to involve synthesis of autocrine growth factors or the inhibition of basal extracellular signal-regulated kinase (ERK) activity but was inhibited by a dominant negative Ras mutant, indicating that MKP-1 enhances Ras-dependent activation of Raf-1 in a cell autonomous manner. This study demonstrates positive feedback regulation of Raf-1 and MKK by the MKP-1 immediate early gene and a potential mechanism for activating Raf-1/MKK signaling pathways alternative to those involving ERK.
Shapiro
P S
PS
Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309, USA.
Ahn
N G
NG
D016475:3T3 Cells; D000818:Animals; D018797:Cell Cycle Proteins; D019281:Dimerization; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation; D005246:Feedback; D017874:Immediate-Early Proteins / Q000378:metabolism*; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D012694:Serine / Q000378:metabolism
D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D012694:Serine; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases