POLYAMINE-MEDIATED DEGRADATION OF ORNITHINE DECARBOXYLASE IN CHINESE HAMSTER OVARY CELLS.

Persistent Link:
http://hdl.handle.net/10150/184002
Title:
POLYAMINE-MEDIATED DEGRADATION OF ORNITHINE DECARBOXYLASE IN CHINESE HAMSTER OVARY CELLS.
Author:
GLASS, JAMES RUSSELL.
Issue Date:
1987
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The objective of this research was to identify specific mechanisms involved in the regulation of ornithine decarboxylase, the first enzyme in the polyamine biosynthetic pathway. Immunochemical techniques were used to study post-translational modifications of the ODC protein in relation to activity alterations. Initial experimentation showed that Chinese hamster cells maintained in a defined medium express an ODC protein stable to intracellular degradation. Treatment of these cells with exogenous ornithine or polyamines resulted in a rapid loss of enzyme activity, without detectable changes in the enzyme specific activity. The loss of enzyme activity was a result of accelerated ODC degradation, as determined by immunoprecipitation of pre-labeled protein. In addition, spermidine, but not ornithine, totally inhibited new ODC synthesis. The mechanism of accelerated ODC degradation was investigated and found to occur by an apparent novel mechanism. Degradation of ODC was both ubiquitin-independent and non-lysosomal, and there was also no detectable accumulation of a modified form of ODC protein. In addition, it was found that a component of protein synthesis is required for this process, as inhibitors (cycloheximide, emetine, puromycin) blocked polyamine-accelerated degradation. ODC cDNA was used to synthesize both ODC specific mRNA and protein using in vitro synthesis. These systems may allow the generation of sufficient quantities of material which can be used to recreate in vitro the specific components involved in polyamine inhibition of ODC synthesis and the protease(s) responsible for degradation. The major finding of this work is the direct demonstration that ODC is a stable intracellular protein in the absence of putrescine and spermidine depleted cells (Chapter 2). In addition, that degradation occurs by a novel mechanism, with a requirement for some component of protein synthesis (Chapter 3). Finally, these studies describe the in vitro production of ODC protein and mRNA, which should facilitate further studies of polyamine regulation of ODC degradation and synthesis (Chapter 4).
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Decarboxylases.; Amino acids.; Polyamines.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Molecular and Cellular Biology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Gerner, Eugene

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titlePOLYAMINE-MEDIATED DEGRADATION OF ORNITHINE DECARBOXYLASE IN CHINESE HAMSTER OVARY CELLS.en_US
dc.creatorGLASS, JAMES RUSSELL.en_US
dc.contributor.authorGLASS, JAMES RUSSELL.en_US
dc.date.issued1987en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe objective of this research was to identify specific mechanisms involved in the regulation of ornithine decarboxylase, the first enzyme in the polyamine biosynthetic pathway. Immunochemical techniques were used to study post-translational modifications of the ODC protein in relation to activity alterations. Initial experimentation showed that Chinese hamster cells maintained in a defined medium express an ODC protein stable to intracellular degradation. Treatment of these cells with exogenous ornithine or polyamines resulted in a rapid loss of enzyme activity, without detectable changes in the enzyme specific activity. The loss of enzyme activity was a result of accelerated ODC degradation, as determined by immunoprecipitation of pre-labeled protein. In addition, spermidine, but not ornithine, totally inhibited new ODC synthesis. The mechanism of accelerated ODC degradation was investigated and found to occur by an apparent novel mechanism. Degradation of ODC was both ubiquitin-independent and non-lysosomal, and there was also no detectable accumulation of a modified form of ODC protein. In addition, it was found that a component of protein synthesis is required for this process, as inhibitors (cycloheximide, emetine, puromycin) blocked polyamine-accelerated degradation. ODC cDNA was used to synthesize both ODC specific mRNA and protein using in vitro synthesis. These systems may allow the generation of sufficient quantities of material which can be used to recreate in vitro the specific components involved in polyamine inhibition of ODC synthesis and the protease(s) responsible for degradation. The major finding of this work is the direct demonstration that ODC is a stable intracellular protein in the absence of putrescine and spermidine depleted cells (Chapter 2). In addition, that degradation occurs by a novel mechanism, with a requirement for some component of protein synthesis (Chapter 3). Finally, these studies describe the in vitro production of ODC protein and mRNA, which should facilitate further studies of polyamine regulation of ODC degradation and synthesis (Chapter 4).en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDecarboxylases.en_US
dc.subjectAmino acids.en_US
dc.subjectPolyamines.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineMolecular and Cellular Biologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorGerner, Eugeneen_US
dc.identifier.proquest8709892en_US
dc.identifier.oclc698372315en_US
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