The role of protein kinase C and MARCKS inv-Src- andv-Fps-induced intracellular signaling.
Item
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Title
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The role of protein kinase C and MARCKS inv-Src- andv-Fps-induced intracellular signaling.
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Identifier
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AAI9224827
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identifier
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9224827
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Creator
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Joseph, Cecil Keith.
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Contributor
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Adviser: David A. Foster
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Date
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1992
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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 | Chemistry, Biochemistry
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Abstract
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Activation of Protein Kinase C (PKC) by tumor promoting phorbol esters leads to the phosphorylation of 67 kilodalton and 80 kilodalton proteins in avian and mammalian cells respectively. We demonstrate that activating the protein tyrosine kinase (PTK) activity of the oncogene products v-Src and v-Fps in cells infected with temperature sensitive (ts) derivatives of v-src and v-fps, results in rapid phosphorylation of a 67 kilodalton protein in chicken embryo fibroblasts (CEF), and an 80 kilodalton protein in murine fibroblasts. This protein known as the myristoylated alanine-rich C kinase substrate (MARCKS), was not phosphorylated when cells expressing v-Src and v-Fps were incubated in the presence of protein kinase inhibitors, or exposed to prolonged treatment with phorbol esters to down-regulate PKC. The kinetics of v-Src-induced increases in the physiological activator of PKC, diacylglycerol, correlated with v-Src-induced phosphorylation of MARCKS. Consistent with v-Src and v-Fps using a PKC-mediated pathway to transduce signals, we find that phosphorylation of MARCKS in response to the PTK activity of v-Src and v-Fps, correlates with expression of the PKC-responsive 9E3 gene in CEF, and the TIS10 gene in murine fibroblasts. We conclude that activation of PKC is an early event in signals which are initiated by v-Src and v-Fps.;In BALB/c-3T3 cells stably transformed by v-Src, phorbol esters were unable to induce phosphorylation of MARCKS. Both PKC protein levels and kinase activity was unchanged in v-Src-transformed relative to the parental non-transformed BALB/c 3T3 cells. Thus, the inability to induce MARCKS phosphorylation was not due to a lack of PKC. MARCKS protein levels were found to be reduced in v-Src-transformed cells relative to the parental non-transformed cells. MARCKS RNA levels were also correspondingly reduced in v-Src-transformed cells. Nuclear "run-on" assays showed decreased transcription of MARCKS in v-Src-transformed cells. Thus, the absence of MARCKS in v-Src-transformed cells could be explained by a down-regulation of MARCKS transcription. Inhibiting the protein tyrosine kinase activity of v-Src restored MARCKS RNA levels, MARCKS transcription, and MARCKS protein suggesting that down-regulation of MARCKS in v-Src-transformed BALB/c 3T3 cells is a direct effect of the PTK activity of v-Src. These data implicate MARCKS in maintaining cells in the non-transformed state.
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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.
