Grant: Master's Award: Canada Graduate Scholarships

Infection by pathogens remains a global health priority because many pathogens evolved mechanisms that bypass the immune system, which otherwise protects our bodies. Thus, we hope to better understand our immune system in order to better understand how to defeat pathogens. Macrophages are immune cells that hunt and engulf pathogens into a new organelle called the phagosome.Phagosomes are then transformed into phagolysosomes by fusing with lysosomes, which are very acidic and hydrolytic organelles, killing and digesting the pathogen.Thus, lysosomes are intimately linked to immune clearance of pathogens. Lysosome biogenesis is up-regulated by increased expression of lysosome genes via the TFEB-family of transcription factors. TFEB is stimulated by conditions that require more lysosome, like autophagy that degrades the compartments of its own cell during starvation.We have three hypotheses that I will test. First, since phagosomes need lysosomes for maturation, we hypothesize that phagocytosis triggers TFEB-mediated increase in lysosome gene expression. Second, I will show that inflammatory signals like bacterial products that activate immune cells, but not non-inflammatory signals like apoptotic bodies (dead cells) will increase lysosome gene expression to better prepare cells to fight off pathogens.To do test this, I will transfect and express fluorescent TFEB in RAW macrophages. I will then challenge cells with inflammatory signals, like antibody-coated particles and bacterial products, and non-inflammatory signals like cellular debris, and examine the location of TFEB by microscopy. Importantly, my preliminary data already show that antibody-mediated phagocytosis leads to TFEB stimulation. We will employ pharmacological and gene silencing methods to dissect the signaling pathways that control TFEB and use qRT-PCR to show increased lysosome gene expression after phagocytosis.