Regulation of urokinase-type plasminogen activator expression by an ERK1-dependent signaling pathway in a squamous cell carcinoma cell line.
The urokinase-type plasminogen activator contributes to tissue remodeling by controlling the synthesis of the extracellular matrix-degrading plasmin. We undertook a study to determine the role of the extracellular signal-regulated kinases (ERKs) in the regulation of urokinase-type plasminogen activator expression in a squamous cell carcinoma cell line (UM-SCC-1) that contains a transcriptionally activated urokinase-type plasminogen activator gene. Transient transfection studies using a CAT reporter driven by the urokinase-type plasminogen activator promoter, which had progressive 5' deletions or which had been point-mutated, indicated the requirement of binding sites for AP-1 (-1967) and PEA3 (-1973) for its maximal activation. Expression of a mutant jun protein, which lacks the transactivation domain, caused a dose-dependent repression of a CAT reporter driven by either the urokinase-type plasminogen activator promoter or three tandem AP-1 repeats upstream of a thymidine kinase minimal promoter indicating the importance of AP-1-binding transcription factor(s) in the regulation of urokinase-type plasminogen activator synthesis. Mobility shift assays with UM-SCC-1 nuclear extract revealed binding of fos and junD proteins to an oligonucleotide spanning the AP-1 site at -1967. In-gel kinase assays indicated the constitutive activation of ERK1, which regulates fos synthesis via phosphorylation of p62TCF, but not ERK2, in UM-SCC-1 cells. Moreover, the expression of a dominant-negative ERK1, but not ERK2, repressed urokinase-type plasminogen activator promoter activity. Similarly, interfering with the function of the c-raf serine-threonine kinase, which lies upstream of ERK1, by the expression of a kinase-inactive c-raf repressed the activity of a CAT reporter driven by either the urokinase-type plasminogen activator promotor or tandem AP-1 repeats. These data suggest that urokinase-type plasminogen activator expression in UM-SCC-1 cells is regulated partly by an ERK1, but not ERK2, -dependent signaling pathway.
Lengyel
E
E
Department of Tumor Biology/Head and Neck Surgery, M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
Gum
R
R
Stepp
E
E
Juarez
J
J
Wang
H
H
Boyd
D
D
D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D016758:Genes, jun; D006801:Humans; D016296:Mutagenesis; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics* / Q000378:metabolism
D016761:Oncogene Proteins v-fos; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C065788:transcription factor PEA3; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D014568:Urokinase-Type Plasminogen Activator