Undergraduate Honors Theses

Thesis Defended

Spring 2011

Document Type

Thesis

Department

Molecular, Cellular, & Developmental Biology

First Advisor

Dr. Robert Poyton

Abstract

Hypoxic stress occurs when a cell is exposed to below normal (2-20µM) oxygen concentrations. To survive, the cell must activate necessary genes that regulate hypoxic cell function and metabolism. Hypoxic genes in mammalian cells are activated by transcription factors known as Hypoxic Inducible Factors (HIFs). HIF is regulated by hypoxic stabilization of the HIF-α subunit; however the mechanism of HIF-α stabilization has not been unequivocally determined. Under hypoxic conditions, evidence suggests that the mitochondrial respiratory chain is required for HIF-α stabilization. The electron transport chain produces superoxide and nitric oxide, species that may serve as an intracellular signal. While the current body of literature supports a role of superoxide in hypoxic HIF-α stabilization, the goal of this study was to determine the role of mitochondrial nitric oxide involvement in mediating the regulation of HIF-α. Nitric oxide and superoxide readily react to form peroxynitrite, a potent nitrating agent, which adds nitro groups to tyrosines and carbonylates proteins. Here, I find that following a shift to 1% oxygen for three hours, human embryonic kidney cells, HEK293, exhibit a nitric oxide dependent increase in tyrosine nitration as well as protein carbonylation. Furthermore, preliminary studies demonstrate that cytochrome c oxidase produces the nitric oxide. These findings suggest a possible role of protein tyrosine nitration and/or carbonylation as a signaling mechanism during hypoxic stress.

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