Date of Graduation

5-2016

Document Type

Dissertation (PhD)

Program Affiliation

Microbiology and Molecular Genetics

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Danielle Garsin, Ph.D.

Committee Member

Swathi Arur, Ph.D.

Committee Member

Ambro van Hoof, Ph.D.

Committee Member

Kevin Morano, Ph.D.

Committee Member

Heidi Kaplan, Ph.D.

Abstract

The ability to respond to hostile environmental conditions is critical for the survival of an organism. Oxidative stress is an adverse state in which reactive oxygen species (ROS) accumulate to a harmful level and, if left unresolved, can lead to cellular dysfunction and organismal disease. Sophisticated detoxification systems, characterized by a battery of enzymatic antioxidants, are utilized to neutralize ROS thereby reducing stress. However, ROS are also purposefully produced by designated cellular enzymes to facilitate the signaling and regulation of critical physiological processes. Therefore, both the production and neutralization of ROS must be tightly controlled. Indeed, the expression of detoxification enzymes is regulated by major oxidative stress response transcription factors, such as Nrf2 and SKN-1 in mammals and the model organism Caenorhabditis elegans, respectively. The activity of both Nrf2 and SKN-1 is highly regulated and many conserved mechanisms are used to facilitate proper control of these two transcription factors, making C. elegans a powerful tool in which to study the complex regulation of the major oxidative stress response transcription factors.

Herein, we uncover a novel mechanism of SKN-1 regulation, in which a thioredoxin, TRX-1, negatively impacts the intestinal subcellular localization of this transcription factor in a cell non-autonomous manner from the ASJ neurons. This function of TRX-1 is specific, as SKN-1 regulation is not a common role for other C. elegans thioredoxins. Moreover, SKN-1 regulation is a redox-independent function of TRX-1 and does not impact transcriptional activation or previously characterized SKN-1-dependent protective responses, such as the oxidative or pathogen stress responses. Thioredoxins are understudied in C. elegans, but play an important role in worm lifespan. RNA Seq was used as an unbiased approach to determine potential physiological role(s) of TRX-1. Uncovered associations include changes in the expression of genes involved in collagen biosynthesis and lipid metabolism. In summary, TRX-1 regulates SKN-1 in a manner which dissects subcellular localization and transcriptional activation, emphasizing the importance of strict regulation of SKN-1 activation.

Keywords

TRX-1, SKN-1, cell non-autonomous regulation, oxidative stress response, C. elegans