A glutaredoxin in the mitochondrial intermembrane space has stage-specific functions in the thermo-tolerance and proliferation of African trypanosomes

Abstract

Trypanosoma brucei glutaredoxin 2 (Grx2) is a dithiol glutaredoxin that is specifically located in the mitochondrial intermembrane space. Bloodstream form parasites lacking Grx2 or both, Grx2 and the cytosolic Grx1, are viable in vitro and infectious to mice suggesting that neither oxidoreductase is needed for survival or infectivity to mammals. A 37 °C to 39 °C shift changes the cellular redox milieu of bloodstream cells to more oxidizing conditions and induces a significantly stronger growth arrest in wildtype parasites compared to the mutant cells. Grx2-deficient cells ectopically expressing the wildtype form of Grx2 with its C31QFC34 active site, but not the C34S mutant, regain the sensitivity of the parental strain, indicating that the physiological role of Grx2 requires both active site cysteines. In the procyclic insect stage of the parasite, Grx2 is essential. Both alleles can be replaced if procyclic cells ectopically express authentic or C34S, but not C31S/C34S Grx2, pointing to a redox role that relies on a monothiol mechanism. RNA-interference against Grx2 causes a virtually irreversible proliferation defect. The cells adopt an elongated morphology but do not show any significant alteration in the cell cycle. The growth retardation is attenuated by high glucose concentrations. Under these conditions, procyclic cells obtain ATP by substrate level phosphorylation suggesting that Grx2 might regulate a respiratory chain component.

The Cross Talk between TbTim50 and PIP39, Two Aspartate-Based Protein Phosphatases, Maintains Cellular Homeostasis in Trypanosoma brucei

“…These include glycerol kinase, hexokinase, triose phosphate isomerase, ribokinase, phosphoenol pyruvate carboxy kinase, and fumarate reductase (Table 1). Glutaredoxin, which is a redox-regulatory protein in the mitochondrial IMS and cytosol (39), was upregulated about 2-fold in TbTim50 knockdown cells (Table 1). Among the downregulated proteins, we found a number of chaperone proteins, like Hsp70 (both mitochondrial and cytosolic), DNAj, glucose-regulated protein 78 (GRP78), cyclophilin, and calreticulin (Table 2 and Data Set S1).…”

The lineage-specific, intrinsically disordered N-terminal extension of monothiol glutaredoxin 1 from trypanosomes contains a regulatory region

“…1A ), a CA(Y/F)S active site sequence and a C-terminal GG motif that lacks the Cys residue 8 , 18 . Reverse genetic experiments conducted on Trypanosoma brucei ( Tb ) have shown that 1CGrx1 is the only Grx indispensable for the clinically relevant form of the parasite 8 , 19 – 21 and its function is linked to FeS cluster biogenesis 8 , 22 . The long N-terminal extension conserved among Kinetoplastids has been proposed to promote the non-covalent dimerization of the Grx domain 8 , 19 .…”

Glutaredoxin 1 Deficiency Leads to Microneme Protein-Mediated Growth Defects in Neospora caninum

“…They are involved in various physiological processes, such as transport of Fe-S clusters, apoptosis, DNA synthesis, cell proliferation, cell signal transduction, and immune defense ( Lillig et al, 2008 ; Allen and Mieyal, 2012 ). However, only a few Grxs from parasites have been reported, mainly on trypanosomes and Plasmodium ( Mohring et al, 2017 ; Ebersoll et al, 2018 ). This study characterized two N. caninum Grxs and explained the role of Grx1 in oxidative stress and parasite growth.…”

“…In the bloodstream stage, TbGrx2 is not essential in vitro or in vivo , but under fever-like conditions in the mammalian host, TbGrx2 deficiency leads to an increase in thermotolerance. In the procyclical stage, TbGrx2 deficiency significantly affects the morphology of the parasite and leads to irreversible proliferation arrest ( Ebersoll et al, 2018 ).…”