Signal transduction and cell transformation of receptor-like protein tyrosine kinase Ros.
Item
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Title
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Signal transduction and cell transformation of receptor-like protein tyrosine kinase Ros.
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Identifier
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AAI9908389
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identifier
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9908389
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Creator
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Zong, Cong.
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Contributor
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Adviser: Lu-Hai Wang
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Date
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1998
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Cell | Biology, Molecular
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Abstract
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The transforming gene of avian sarcoma virus UR2, v-ros, encodes a receptor-like protein tyrosine kinase (PTK). To identify the pathways and signaling molecules important for Ros-mediated cell transformation, two approaches were taken.;The first approach employed loss-of-function mutants to correlate their functional impairment with specific defects in signal transduction. Among the mutants of P68{dollar}\sp{lcub}\rm gag-ros{rcub}{dollar}, F419 and DI are particularly interesting since they retain wild type PTK and mitogenic activities, but have dramatically reduced oncogenicity. Both mutants are able to activate the Ras/MAP kinase pathway. However, F419 protein is unable to induce tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) and to promote its association with phosphatidylinositol 3 (Pl3) kinase. In contrast, the DI protein is normal in those respects suggesting that phosphorylation of IRS-1 and activation of Pl3 kinase may be important but not sufficient for Ros-induced transformation. Both mutant proteins display reduced ability to induce tyrosine phosphorylation of a series of cytoskeleton and cell-cell interacting proteins. Thus, the F419 and DI mutations define the v-Ros sequences important for cytoskeleton signaling, and the impairment of which correlates with reduced cell growth in soft agar. Analysis of other mutants suggested that Y414, Y418 and Y419 play an important role in modulating the Ros PTK activity, whereas Y564 is important for v-Ros autophosphorylation, and phosphorylation of phospholipase C{dollar}\gamma{dollar}, whose activation, however, appears not to be essential for v-Ros-induced transformation.;In the second approach, dominant negative (dn) mutants were used to assess the role of Stat signaling in Ros-induced cell transformation. Stat3 was specifically activated by Ros in NIH 3T3 cells. Therefore, dnStat3 mutants were introduced into NIH 3T3 cells expressing a EGFR-Ros chimera which had been shown to induce transformation in response to EGF. Co-expressing the dnStat3 mutant with EGFR-Ros resulted in a dramatic inhibition of this receptor PTK-mediated colony forming activity, but having only a mild effect on mitogenicity of the cells in monolayer. The inhibition of Ros-induced anchorage independent growth of cells correlated with inhibition of the DNA binding and transcriptional activities of Stat3. Therefore, activation of Stat3 plays an important role in the establishment and maintenance of Ros PTK-induced anchorage independent growth.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
