Metabolic regulation of macrophage function during M. tuberculosis infection



 DESCRIPTION (provided by applicant): Macrophages serve the dual role as the host cell for M. tuberculosis and the cell that is primarily responsible for eliminating infection. Macrophage activation by the cytokine IFN- γ is the cornerstone of effective immune responses to M. tuberculosis. There are still gaps in our understanding of the molecular mechanisms by which IFN- γ activates macrophages to kill M. tuberculosis. In this application we explore connections between macrophage metabolism, IFN- γ activation and control of M. tuberculosis replication. The concept that flux through specific metabolic pathways impacts gene expression and pathways of differentiation in immune cells is an emerging area of interest. Enzymes and metabolites of glycolysis have been found to impact specific mechanisms of transcription and translation in multiple immune cells including macrophages. Understanding how metabolism impacts macrophage function has important consequences for understanding the survival of pathogens such as Mycobacterium tuberculosis (Mtb) that exploit macrophages as a host cell. The long term- goal of this work is to understand how aerobic glycolysis in macrophages impacts infection with M. tuberculosis. We have found that IFN- γ activated macrophages infected with M. tuberculosis engage in aerobic glycolysis resulting in stabilization of the transcription factor HIF-1a and that this response is required for IFN- γ based control of M. tuberculosis infection. In aim 1 we propose to identify specific enzymes that are required to support enhanced glycolytic flux observed in M. tuberculosis infected and IFN- γ activated macrophages, and to use this knowledge to genetically manipulate glycolysis during M. tuberculosis infection. In aim 2 we define the relationship between aerobic glycolysis and stabilization of the transcription factor HIF-1a, and identify macrophage-signaling pathways that are controlled by HIF-1a and/or aerobic glycolysis. Finally, in aim three we will test the hypothesis that HIF-1a regulation of genes that participate in selective autophagy is important for IFN- γ based control of M. tuberculosis infection. If successful, the proposed work will open up a new dimension to our understanding of immune control of M. tuberculosis that can help illuminate the development of novel immune therapeutics.