A Molecular Mechanism for DEPTOR in the Control of Cellular Metabolism and Disease

Abstract

One of the main hubs of cellular metabolic integration is the mechanistic target of rapamycin, or mTOR. In normal, healthy cells, mTOR helps to regulate and balance cellular growth and proliferation against metabolic conservation and maintenance. However, when cellular conditions deteriorate due to environmental stressors or genetic mutations, mTOR’s contribution towards normal cellular metabolism can become dysregulated, leading to a number of disease states in different tissues, including type 2 diabetes, a large percentage of human cancers, Parkinson’s disease, Alzheimer’s disease, cancer cachexia, and many effects of ageing. One of the primary regulators of mTOR activation is DEPTOR, a potent endogenous inhibitor of mTOR. The purpose of this dissertation is to mechanistically define the role of DEPTOR protein expression in regulating cellular metabolism under various conditions. While the direct relationship between DEPTOR and mTOR has been explored under some steady state conditions, there are only a handful of studies that have explored the use of directed changes in DEPTOR protein content as a means to regulate mTOR activity. By taking advantage of recently developed precision gene editing technologies, we have shown that the chronic and constitutively active expression of DEPTOR protein can act as a potent regulator of cellular anabolism through mTOR in both the normal, healthy C2C12 murine myoblast, and in MCF7 human epithelial cancer cells. This approach offers a number of benefits over pharmacological inhibition of mTOR or of upstream signaling proteins, as those strategies often suffer from a lack of specificity, have inherent cytotoxic properties, or eventually become ineffective due to altered feedback mechanisms. The current experiments are the first to demonstrate a causative relationship between DEPTOR expression, the resultant mTOR activity, and eventual downstream anabolic function. In addition, the outcomes contained within this dissertation indicate the possibility that certain anabolically aggressive diseases may be treated through directed changes in DEPTOR protein content