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Characterizing the mechanism of trogocytosis in Entamoeba histolytica

E. histolytica (histo‐: tissue; lytic‐: dissolving) is a eukaryotic pathogen that can invade and destroy intestinal tissue. Tissue damage is likely to result from direct, contact‐dependent killing of human cells by amoebae. An improved understanding of this process would allow us to define the mechanism of pathogenesis. Our lab discovered that amoebae kill human cells by ingesting “bites,” an unusual strategy for cell warfare termed trogocytosis (trogo‐: nibble). The mechanism underlying trogocytosis, i.e. how an amoeba extracts bites from a living human cell, is unknown. Interestingly, amoebae ingest dead human cells whole via phagocytosis (phago‐: devour). While some aspects are shared with phagocytosis, nibbling is different from eating entire cells. Therefore, I hypothesize that, while some aspects are likely shared with phagocytosis, amoebic trogocytosis also requires signaling machinery distinct from phagocytosis. I aim to identify and characterize genes required for E. histolytica trogocytosis by using two complementary approaches: transcriptomics analysis and forward genetics. There is evidence that both phagocytosis and trogocytosis are transcriptionally regulated in E. histolytica, thus I am using RNA‐seq analysis to examine differential gene expression in amoebae undergoing trogocytosis versus phagocytosis. My preliminary results with imaging flow cytometry have established a method to quantify and optimize the number of amoebae performing either trogocytosis or phagocytosis respectively, setting the stage for RNA‐seq analysis. Preliminary studies for the forward genetics selection approach provide proof of principle that ingestion mutants can be isolated by selection. Results from these approaches will help to define the mechanism for trogocytosis. Since trogocytosis appears to be a fundamental form of eukaryotic cell‐cell interaction that is exaggerated and exploited for cell killing by microbes, a deeper understanding of the mechanism will have broad impact.