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UBC Theses and Dissertations

Leishmania donovani upregulates host macrophage Argonaute 1 to persist inside infected host, and quantitative proteomic analysis of RNA-induced silencing complex isolated from infected host Moradimotlagh, Atieh


Leishmania is a protozoan parasite that causes a wide range of diseases collectively known as leishmaniasis, which differ in symptoms and severity throughout various clinical forms, including cutaneous, mucocutaneous, and visceral. It is well established that Leishmania exploits the cell biology of host macrophages for successful infection and persistence inside the host. Identification and characterization of Leishmania interactions with host cellular proteins/pathways and the functional consequences of these interactions can pave the way to develop novel anti-leishmanial strategies targeted at these interactions. To date, our understanding of the molecular mechanisms associated with the pathogenicity of Leishmania infection is still limited. RNA silencing pathways—collectively referred to as RNA interference—participates in the regulation of various biological processes in most eukaryotic cells. It is becoming increasingly clear that several intracellular pathogens target host cell RNA interference pathways to promote their survival. In this study, we investigated the potential role of host macrophage Argonautes in Leishmania pathogenesis and found Leishmania macrophage Argonaute 1 (Ago1) was selectively and significantly more abundant than that of non-infected control, suggesting that Ago1 plays a role in pathogenicity. In fact, siRNA-mediated downregulation of Ago1 enhanced Leishmania clearance from infected host cells, linking macrophage Ago1 to Leishmania virulence. To investigate the mechanisms of host Ago1 in Leishmania pathogenesis, we employed whole proteome approach which showed that expression of several previously reported Leishmania pathogenesis-related proteins were dependent on the level of macrophage Ago1. Moreover, detailed biochemical analysis showed that Leishmania modulated host RNA-Induced Silencing Complex (RISC) composition during infection, strongly suggesting macrophage RISC targeting. Strikingly, Leishmania proteins were detected as part of host RISC in infected cells. Together, our results identify novel macrophage-Leishmania-RNAi related interactions that could potentially be exploited for anti-leishmanial and therapeutic purposes.

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