A low molecular weight factor from dividing cells activates phospholipase D in caveolae-related membrane microdomains.
Item
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Title
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A low molecular weight factor from dividing cells activates phospholipase D in caveolae-related membrane microdomains.
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Identifier
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AAI9946148
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identifier
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9946148
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Creator
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Bychenok, Sergey.
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Contributor
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Adviser: David A. Foster
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Date
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1999
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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, Molecular | Health Sciences, Oncology
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Abstract
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Lipids play an important role as precursors for a number of mitogenic signaling molecules. Phosphatidylcholine (PC), a major phospholipid of cellular membranes, is a significant source for these molecules. The principal reaction of phosphatidylcholine hydrolysis is catalyzed by PC-specific phospholipase D (PLD). Phosphatidic acid, a primary metabolite of this reaction, has been shown to have mitogenic properties by itself as well as serving as a precursor for other lipid second messengers.;PLD activity is elevated in cells transformed by a number of oncogenes including v-Ras. It is believed that increase in the PLD activity contributes directly to acquisition of a transformed phenotype in these cells. Molecular mechanisms regulating PLD activity in v-Ras-transformed cells are not yet well understood. In this report we present evidence that a small molecular weight cytosolic factor is responsible for increased PLD activity in v-Ras-transformed cells.;The large difference in PLD activity between the Ras-transformed and non-transformed parental cells disappeared in membranes isolated from these two cell lines. In reconstitution experiments, heat-denatured cytosolic fractions from Ras-transformed, but not from parental NIH 3T3 cells, elevated PLD activity in isolated membranes. This heat-resistant PLD-stimulating activity from the Ras-transformed cells was sensitive to proteases and passed through a 1 kDa MW cut-off membrane, suggesting that the factor is a peptide of less than 10 amino acids. The ability of this PLD-stimulating factor, designated PLD-SF, to elevate PLD activity in isolated membranes was restricted to the caveolae-enriched light membranes, where many signaling molecules, including Ras, are localized. PLD-SF was also elevated in v-Src- and v-Raf-transformed cells and in serum-stimulated NIH 3T3 cells. PLD-SF was detected in a variety of rat tissues, but was highest in testes, where a large percentage of cells are dividing. A similar low molecular weight PLD stimulating activity was found in actively dividing, but not stationary yeast cells. The data here provide evidence for a ubiquitous PLD-stimulating peptide that is elevated in dividing cells.
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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.
