Text

ETD_2052

http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051886

theses

Contrary to an initial understanding of necrosis as a chaotic, non-regulated type of cell death, recent studies suggest that necrotic cell death (NCD) is a consequence of a complex and lethal cascade of genetically-encoded events. Necrosis underlies the pathology of many neurodegenerative diseases, stroke, and traumatic injury. In the Driscoll Lab, NCD mechanisms have been addressed for several years taking advantage of unique genetic and molecular biology tools developed in the model organism Caenorhabditis elegans. The necrotic paradigm we study the most involves initiation of cell death by hyperactivated ion channels expressed in six touch-sensory neurons and requires elevation of intracellular Ca2+, which activates calpain and cathepsin proteases.
I exploited the unique features of our model system to uncover novel genetic factors influencing this process. To this end, I conducted a high-throughput forward genetic screen to identify mutations that block or delay necrotic cell death induced by MEC-4(d) channel hyperactivation, and genetically mapped novel mutations capable of blocking or slowing the death process. I exploited an automated mutational screening capacity that allows sorting of individual animals based on detection of fluorescent signals that, in our particular case, had been engineered to indicate neuronal viability. I focused on the cloning of two novel mutant loci and dissected molecular mechanisms responsible for death suppression. In addition, I studied the impact of a major subset of calcium homeostasis genes in a C. elegans model of Aβ toxicity.
My research adds a new component to the current understanding of NCD, suggesting that inability to cope with endoplasmic reticulum stress (presumably induced by calcium depletion inside the ER, which affects chaperone functionality) plays an important role in progression through necrosis. I discovered that mild activation of an intact unfolded protein response (UPR), e.g., as induced by downregulation of UDP-glucose:glycoprotein glucosyltransferase (UGGT, an ER-resident enzyme involved in high-fidelity protein folding quality control) or mild increments in ambient temperature, can partially suppress necrosis in our C. elegans model, reminiscent of beneficial preconditioning effects in mammals. Additionally I found that several UPR transducers contribute to such modulation of cell death in a “tug-of-war” fashion. Our refined model of molecular mechanisms contributing and modulating necrosis suggests new strategies that could eventually limit the devastating effects of necrosis in human injury and disease.

Ph.D.

Includes bibliographical references (p. 154-174)

by Yury Orlando Nunez Lopez

doi:10.7282/T3M61KDJ

ETD doctoral

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