Date of Award

12-1997

Degree Name

Master of Science

Department

Biological Sciences

First Advisor

Dr. Susan Stapleton

Second Advisor

Dr. David Reinhold

Third Advisor

Dr. Leonard Beuving

Access Setting

Masters Thesis-Open Access

Abstract

Insulin has a wide range of metabolic and mitogenic effects in cells. The mechanism of insulin action in controlling these events is not well understood, but involves, at least in part, a complex phosphorylation cascade. Selenate has been shown to mimic insulin on several metabolic processes, including the regulation of glucose-6-phosphate dehydrogenase (G6PDH) gene expression. Its mechanism of action, however, is not known. To investigate the mechanisms of insulin and selenate action on the regulation of G6PDH, signal proteins from primary rat hepatocytes were first studied. Insulin and sodium selenate similarly increased tyrosyl phosphorylation of the β-subunit of the insulin receptor and insulin receptor substrate- 1, as determined by Western analysis. Insulin and selenate also significantly increased mitogen-activated protein (MAP) kinase activity, as determined by an in-gel activity assay, through a Ras-dependent pathway. Insulin's effects were typically rapid and transient, whereas selenate's effects were delayed in onset and sustained for hours. MAP kinase activation did not appear to be required for insulin-induced G6PDH expression, and expression may not be due to a rapamycin-sensitive pathway. Selenate induction of G6PDH expression was sensitive to the effects of rapamycin.

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Biology Commons

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