Role of Tyrosine Kinase Activity of Epidermal Growth Factor Receptor in the Lysophosphatidic Acid-stimulated Mitogen-activated Protein Kinase Pathway*
- Jess M. Cunnickद,
- Jay F. Dorsey‡§,
- Todd Standley‡,
- James Turkson‡‖,
- Alan J. Kraker‡,
- David W. Fry‡,
- Richard Jove‡‖ and
- Jie Wu‡§‖§§
- From the ‡Molecular Oncology Program, H. Lee Moffitt Cancer Center and Research Institute, §Department of Medical Microbiology and Immunology, ‖Department of Biochemistry and Molecular Biology, University of South Florida College of Medicine, Tampa, Florida 33612 and ‡Parke-Davis Pharmaceutical Research, Ann Arbor, Michigan 48105
Abstract
Recent evidence indicates that the epidermal growth factor (EGF) receptor mediates a branch of lysophosphatidic acid (LPA)-induced signal transduction pathways that activate mitogen-activated protein (MAP) kinase. However, it is unclear whether the intrinsic tyrosine kinase activity of EGF receptor is involved. We previously showed that reactive oxygen species (ROS) were involved in the LPA-stimulated MAP kinase pathway. Here, we identify tyrosine phosphorylation of EGF receptor as an LPA signaling step that requires ROS. To evaluate the role of the tyrosine kinase activity of EGF receptor in the LPA-stimulated MAP kinase pathway, we examined the effects of an EGF receptor-specific tyrosine kinase inhibitor, PD158780. PD158780 potently inhibited the LPA-stimulated MAP kinase kinase 1/2 (MKK1/2) activation and EGF receptor tyrosine phosphorylation in HeLa cells, while it had no detectable effect on c-Src kinase activity. PD158780 also inhibited LPA-induced MKK1/2 activation and DNA synthesis in NIH 3T3 cells. Furthermore, we compared LPA-stimulated MKK1/2 and MAP kinase activation, transcriptional activity of the c-fos promoter, and DNA synthesis in B82L cells, which lack endogenous EGF receptor, and B82L cells expressing kinase-defective or wild-type human EGF receptor. Results obtained from analysis of these cell lines suggest that the EGF receptor tyrosine kinase contributes to the LPA-stimulated MAP kinase activation, c-fos transcription, and mitogenesis.
Footnotes
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↵* This work was supported in part by Junior Faculty Research Award JFRA-647 (to J. W.) from the American Cancer Society, American Cancer Society, Florida Division, Grant F96USF-2 (to J. W.), University of South Florida Research and Creative Scholarship Grant (to J. W.), and National Institutes of Health Grant CA55652 (to R. J.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ Supported by Training Grant T32 DA 07245 from the National Institutes of Health.
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↵§§ To whom correspondence should be addressed: Molecular Oncology Program, MDC 44, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Dr., Tampa, FL 33612. Tel.: 813-979-6713; Fax: 813-979-6700; E-mail: wu{at}moffitt.usf.edu.
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↵1 The abbreviations used are: LPA, lysophosphatidic acid; MAP kinase, mitogen-activated protein kinase; MKK1/2, MAP kinase kinase 1 and MAP kinase kinase 2; ROS, reactive oxygen species; EGF, epidermal growth factor; SRE, serum response element; PDGF, platelet-derived growth factor; NAC,N-acetylcysteine.
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↵2 J. M. Cunnick, J. F. Dorsey, Q. Chen, and J. Wu, unpublished data.
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- Received June 17, 1997.
- Revision received March 23, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
