Antoniou, S.; Jones, N.; Geoghegan, V.; Dowle, A.; McNiven, C.; Neish, R.; MacDonald, C.; Wilkinson, A. J.; Mottram, J. C.

Leishmaniasis is caused by Leishmania parasites, which undergo cellular adaptation when transitioning from the insect stage (promastigote) to the mammalian stage (amastigote). While the ubiquitin-proteasome system (UPS) is vital for life cycle progression, global ubiquitination dynamics have remained unmapped. We established a quantitative ubiquitinomics workflow for Leishmania mexicana, identifying over 9,100 ubiquitination sites across 38% of the proteome, revealing thousands of stage-specific regulatory events. Promastigote-enriched sites associate with cell motility, while amastigote-enriched sites link to metabolism and glycosome organization. We identified extensive ubiquitination on UPS components, including the essential virulence factor deubiquitinase 2 (DUB2). Using inducible gene deletion and XL-BioID proximitomics, we identified 111 potential DUB2 substrates. High-confidence substrates include the E2 conjugating enzyme UBC2, which is required for differentiation, and SUMO, a critical regulator of ubiquitin crosstalk. The discovery of UBC2 as a substrate of DUB2 directly links ubiquitination with promastigote to amastigote differentiation. Our findings provide a comprehensive map of the Leishmania ubiquitinome and demonstrate that DUB2 acts as a pleiotropic regulator controlling post-translational modifications of essential proteins involved in life cycle progression.