ERK regulation upon contact inhibition in fibroblasts.
Despite the understanding of the importance of mitogen-activated protein (MAP) kinase activation in the stimulation of growth, little is known about the role of MAP kinase regulation during contact inhibited growth control. To investigate the role of the MAP kinase extracellular signal-regulated kinase (ERK) during the transition to a contact inhibited state, cultures of normal fibroblasts (BJ) were grown to different stages of confluency. The levels of MAP kinase phosphatase (MKP) expression and the amount of active ERK and MAP ERK kinase (MEK) in these cultures were assessed through western blot analysis and were compared to fibrosarcoma cell cultures (HT-1080), which lack contact inhibition. In normal fibroblasts, the amounts of active MEK and ERK decline at contact inhibition, concurrently with a rise in MKP-1, MKP-2, and MKP-3 protein levels. In contrast, fibrosarcoma cells appear to lack density-dependent regulation of the ERK pathway. Additionally, altering the redox environment of fibrosarcoma cells to a less reducing state, as seen during contact inhibition, results in increased MKP-1 expression. Taken together, these results suggest that the altered redox environment upon contact inhibition may contribute to the regulation of ERK inactivation by MKPs.
Wayne
Joshua
J
Department of Biology, Monmouth University, West Long Branch, NJ 07764, USA.
Sielski
Jennifer
J
Rizvi
Ahmed
A
Georges
Ketleine
K
Hutter
Dorothy
D
D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D003260:Contact Inhibition / Q000502:physiology*; D054638:Dual Specificity Phosphatase 1; D054642:Dual Specificity Phosphatase 6; D054637:Dual-Specificity Phosphatases; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D054639:Mitogen-Activated Protein Kinase Phosphatases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism
D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D054639:Mitogen-Activated Protein Kinase Phosphatases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; C490583:DUSP4 protein, human; C517035:DUSP6 protein, human; D054638:Dual Specificity Phosphatase 1; D054642:Dual Specificity Phosphatase 6; D054637:Dual-Specificity Phosphatases; D017027:Protein Tyrosine Phosphatases