A lipid droplet triacylglycerol lipase governs neutral lipids mobilization and differentiation of Trypanosoma brucei

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Abstract
Lipid droplets (LD) are dynamic organelles largely distributed in all living cells that are essential notably for membrane biogenesis and cell proliferation. In Trypanosoma brucei , a protozoan parasite responsible for major lethal infectious diseases in humans and cattle, lipid acquisition and mobilization are essential for its survival and adaptation to its different hosts, but the roles of LD in these processes remain largely unknown. To address this gap, we identified and characterized a unique functional orthologue of the human adipose triacylglycerol lipase (ATGL), responsible for the initiation of neutral lipid mobilization, in T. brucei . In this study, we present TbPatatin-like (TbPat), the first ATGL ortholog in protozoan parasites. By combining reverse genetics, microscopy and –omics analysis, we deciphered the role of TbPat in lipolysis and neutral lipid maintenance in both insect and mammalian stages of African trypanosomes and imaged its distribution on the LD surface at an unprecedented resolution by using Cryo-Expansion microscopy. We found that inactivation of TbPat in mammalian form T. brucei led to a global upregulation of the mitochondrial metabolic proteome; furthermore, these cells appeared remarkably unable to differentiate into the procyclic insect stage. Through its expression and localization, TbPat appears to be at an essential checkpoint linking lipid environment and metabolism to more complex cell programs involving proteome, compartment remodeling and lifecycle completion.

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