| Summary: | 碩士 === 國立成功大學 === 藥理學研究所 === 88 === Eps8 is a common substrate of EGF receptor tyrosine kinase and Src. Previous studies have indicated that overexpression of Eps8 and EGFR may enhance DNA synthesis of NIH3T3 or 32D myeloblast cell. Also, in human tumor cells p97Eps8 is highly tyrosyl phosphorylated. Our previous studies indicated that Eps8 was phosphorylated by v-Src mainly on the N-terminal part of Eps8(aa-1 to aa-179). In this attempt to determinate and characterize this tyrosyl phosphorylation site, we performed site-directed mutagenization of the Tyr-28 or -45 residues in this region of p97Eps8. We found that mutation of Tyr-28 to Phe-28 had no effect on the Src-mediated phosphorylate of GST-N-Eps8(aa1 to aa220), while mutation of Tyr-45 to Phe-45 had completely abolished the phosphorylation on this region by Src. Furthermore, when Tyr-45 was mutated to phenylalanine, it had also abolished the focus-forming ability of p97Eps8 in C3H10T1/2 cells. Thus, we speculated that the Src-mediated phosphorylation on the Tyr-45 might be important for p97Eps8 induced anchorage-independent growth.
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