(1)Study of Tyrosine Kinase Activity in Taiwanese Colon Cancer (2)Determination of Src Phosphorylation Sites on eps8
| Autor: | Jung-Hui Wang, 王容慧 |
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| Rok vydání: | 1998 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 86 Protein tyrosine kinases play significant roles in a variety of cellular functions, such as mitogenesis, differentiation, and mobility. Elevation of their expression and enzymatic activity has been closely linked to the development of various forms of cancer. Recently, growing number of tyrosine kinases had been identified in the colorectal cancers. Thus, we are interested to investigate their involvement in human colon cancer in Taiwan. To date, overexpression of EGF receptor, c-Src and FAK, has been reported in colon cancer in western world. Thus, we would like to know whether overexpression of these kinases can also coutribute to the incidence of colon tumor in Taiwanese. To answer this question, whole cell lysates prepared from twenty-one Taiwanese colon cancer specimens were analyzed, and twelve were found to overexpress FAK and c-Src. Interestingly, overexpression of cortactin (c-Src substrate) is observed as well. The presence of enzymatically active kinases in colon tumor specimens can also be demonstrated by in situ gel kinase assays. Another part of my thesis is the determination of tyrosine phosphorylation residues on eps8 that are mediated by v-Src. The epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase. When EGFR is bound, it become dimerized, activated and autophosphorylated itself. The subsequent tyrosine phosphorylation of the EGFR substrates following EGFR activation transduces the mitogenic signal into the cytoplasm and the nucleus leading to cell division.C-Src is a 60-kDa nonreceptor tyrosine kinase whose overexpression potentiates both mitogenic and transforming ability of EGFR in murine fibroblasts. One of the possible mechanisms may be the regulation of common substrates shared by both EGFR and c-Src. One of the EGFR substrates is designated eps8 which representes EGFR-pathway substrate no.8. Our previous studies indicated that eps8 was also highly tyrosyl phosphorylated in v-Src transformed cells. In order to further study the roles of eps8 in EGF-induced signaling pathway, we were interested to know whether phosphorylation of eps8 mediated by v-Src participate in any EGFR-induced signaling pathways. To address this point, a series of GST-fusion proteins spanning over the whole sequence of p97eps8 were constructed and utilized as substrates to identify the potential v-Src-mediated phosphorylation sites in vitro. Our data indicated that at eps8 N-terminus (amino acid 1-179), there was at least one potential Src phosphorylation site . |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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