ATP-independent chaperones are widespread across all domains of life and serve as the first line of defense during protein unfolding stresses. One of the known crucial chaperones for bacterial survival in a hostile environment (e.g., heat and oxidative stress) is the highly conserved, redox-regulated ATP-independent bacterial chaperone Hsp33. Using a bioinformatic analysis, we describe novel eukaryotic homologs of Hsp33 identified in eukaryotic pathogens belonging to the kinetoplastids, a family responsible for lethal human diseases such as Chagas disease as caused by Trypanosoma cruzi, African sleeping sickness caused by Trypanosoma brucei spp., and leishmaniasis pathologies delivered by various Leishmania species. During their pathogenic life cycle, kinetoplastids need to cope with elevated temperatures and oxidative stress, the same conditions which convert Hsp33 into a powerful chaperone in bacteria, thus preventing aggregation of a wide range of misfolded proteins. Here, we focused on a functional characterization of the Hsp33 homolog in one of the members of the kinetoplastid family, T. brucei, (Tb927.6.2630), which we have named TrypOx. RNAi silencing of TrypOx led to a significant decrease in the survival of T. brucei under mild oxidative stress conditions, implying a protective role of TrypOx during the Trypanosomes growth. We then adopted a proteomics-driven approach to investigate the role of TrypOx in defining the oxidative stress response. Depletion of TrypOx significantly altered the abundance of proteins mediating redox homeostasis, linking TrypOx with the antioxidant system. Using biochemical approaches, we identified the redox-switch domain of TrypOx, showing its modularity and oxidation-dependent structural plasticity. Kinetoplastid parasites such as T. brucei need to cope with high levels of oxidants produced by the innate immune system, such that parasite-specific antioxidant proteins like TrypOx – which are depleted in mammals – are highly promising candidates for drug targeting.
Bibliographical noteFunding Information:
We are tremendously thankful to Prof. Bernd Bukau and Dr. Axel Mogk for providing us with the DnaK/DnaJ, GrpE expression system and the purification protocols, for Dror Eliaz for helping set up the Trypanosoma system in our lab, and for Meytal Radzinski for editing and critical reading of the manuscript. Funding. We are grateful for the financial support from the Israel Science Foundation (grant number: 1765/13 and 1537/18), Human Frontier Science program (CDA00064/2014), the United States-Israel Binational Science Foundation (grant number: 2015056), Marie-Curie integration grant (EU FP7 People CIG, 618806), and Neubauer Foundation Fellowship for SA.
© Copyright © 2020 Aramin, Fassler, Chikne, Goldenberg, Arian, Kolet Eliaz, Rimon, Ram, Michaeli and Reichmann.
- holdase chaperone
- redox regulation
- redox regulation in T. brucei
- stress-regulated chaperones