Mitchell Lesko - Durrant and O'Donnell Lab
"Dynamics of Hxk2 dimerization and nuclear translocation and their role in resistance to 2-deoxyglucose in yeast"
Abstract: Glucose is the most commonly used energy source in cells and serves as a building block for many key cellular processes. Hexokinases are central regulators of glucose metabolism, facilitating the first committed step in glycolysis and converting glucose to glucose-6-phosphate. When cancerous cells shift their metabolism to fermentation of glucose in a process called the Warburg effect, these cells become exquisitely dependent upon glucose and the action of hexokinases. As a result, many cancerous cells upregulate hexokinases to drive increased glucose metabolism and fuel rapid proliferation. Hexokinases are conserved across eukaryotes, and here we use S. cerevisiae as a model to study hexokinase function. Yeast is a good model system for these studies as they rapidly ferment glucose, and so already have a ‘Warburg-like’ metabolic shift. Yeast express three hexokinases and hexokinase 2 (Hxk2) is the predominant form in glucose-grown cells. In addition to phosphorylating glucose, Hxk2 helps control the glucose repression pathway, translocating into the nucleus to control transcription of metabolic genes with the transcriptional repressor Mig1. Nuclear shuttling of Hxk2 is regulated by phosphorylation, and this modification also controls the dimer to monomer transition for Hxk2, making these two states intimately linked. Using advanced confocal microscopy and image quantification approaches we refine the model of Hxk2 nuclear shuttling, refuting the long-held view that Hxk2 is nuclear in high-glucose conditions. We expand our understanding of cytosolic-nuclear shutting for Hxk2 by identifying Tda1, a kinase known to control Hxk2’s oligomeric state in response to glucose-depletion, as key for controlling Hxk2 nuclear localization. Finally, we find that mutants of Hxk2, previously shown to promote resistance to a toxic glucose analog, 2-deoxyglucose (2DG), allosterically impede upon Hxk2 substrate binding, and alter its nuclear accumulation. Taken together, our studies provide insight into the critical roles hexokinases play in regulating fundamental metabolic responses in cells. They also provide a glimpse into the mechanisms cancer cells may exploit to gain resistance to metabolic inhibitors that are becoming common place in the development of cancer treatments.
Friday, October 1st, 2021
A219B Langley Hall
12:00 PM