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Regulation of urokinase‐type plasminogen activator expression by an ERK1‐dependent signaling pathway in a squamous cell carcinoma cell line
Author(s) -
Lengyel Ernst,
Gum Rebecca,
Stepp Evan,
Juarez Jose,
Wang Heng,
Boyd Douglas
Publication year - 1996
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19960601)61:3<430::aid-jcb10>3.0.co;2-n
Subject(s) - plasminogen activator , transactivation , microbiology and biotechnology , activator (genetics) , urokinase , urokinase receptor , biology , kinase , phosphorylation , transcription factor , signal transduction , transfection , chemistry , cell culture , biochemistry , gene , endocrinology , genetics
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 jun D 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 p62 1CT , 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. © 1996 Wiley‐Liss, Inc.