Browsing by Author "Singha, Ujjal K."
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Discovery of an ergosterol-signaling factor that regulates trypanosoma brucei growth(2015) Haubrich, Brad A. (TTU); Singha, Ujjal K.; Miller, Matthew B. (TTU); Nes, Craigen R. (TTU); Anyatonwu, Hosanna (TTU); Lecordier, Laurence; Patkar, Presheet (TTU); Leaver, David J. (TTU); Villalta, Fernando; Vanhollebeke, Benoit; Chaudhuri, Minu; Nes, W. David (TTU)Ergosterol biosynthesis and homeostasis in the parasitic protozoan Trypanosoma brucei was analyzed by RNAi silencing and inhibition of sterol C24β -methyltransferase ( TbSMT) and sterol 14α-demethylase [ TbSDM ( TbCYP51)] to explore the functions of sterols in T. brucei growth. Inhibition of the amount or activity of these enzymes depletes ergosterol from cells at <6 fg/cell for procyclic form (PCF) cells or <0.01 fg/cell for bloodstream form (BSF) cells and reduces infectivity in a mouse model of infection. Silencing of Tb SMT expression by RNAi in PCF or BSF in combination with 25-azalanosterol (AZA) inhibited parasite growth and this inhibition was restored completely by adding synergistic cholesterol (7.8 μM from lipid-depleted media) with small amounts of ergosterol (1.2 μM) to the medium. These observations are consistent with the proposed requirement for ergosterol as a signaling factor to spark cell proliferation while imported cholesterol or the endogenously formed cholesta-5,7,24-trienol act as bulk membrane components. To test the potential chemotherapeutic importance of disrupting ergosterol biosynthesis using pairs of mechanismbased inhibitors that block two enzymes in the post-squalene segment, parasites were treated with AZA and itraconazole at 1 μM each (ED50 values) resulting in parasite death . Taken together, our results demonstrate that the ergosterol pathway is a prime drug target for intervention in T. brucei infection. -Haubrich, B. A., U. K. Singha, M. B. Miller, C. R. Nes, H. Anyatonwu, L. Lecordier, P. Patkar, D. J. Leaver, F. Villalta, B. Vanhollebeke, M. Chaudhuri, and W. D. Nes. Discovery of an ergosterol-signaling factor that regulates Trypanosoma brucei growth. J. Lipid Res. 2015.Item Steroidal Antimetabolites Protect Mice against Trypanosoma brucei(2022) Chaudhuri, Minu; Singha, Ujjal K.; Vanderloop, Boden H. (TTU); Tripathi, Anuj; Nes, W. David (TTU)Trypanosoma brucei, the causative agent for human African trypanosomiasis, is an emerging ergosterol-dependent parasite that produces chokepoint enzymes, sterol methyltransferases (SMT), not synthesized in their animal hosts that can regulate cell viability. Here, we report the lethal effects of two recently described natural product antimetabolites that disrupt Acanthamoeba sterol methylation and growth, cholesta-5,7,22,24-tetraenol (CHT) and ergosta-5,7,22,24(28)-tetrae-nol (ERGT) that can equally target T. brucei. We found that CHT/ERGT inhibited cell growth in vitro, yielding EC50 values in the low nanomolar range with washout experiments showing cidal activity against the bloodstream form, consistent with their predicted mode of suicide inhibition on SMT activity and ergosterol production. Antimetabolite treatment generated altered T. brucei cell morphology and death rapidly within hours. Notably, in vivo ERGT/CHT protected mice infected with T. brucei, doubling their survival time following daily treatment for 8–10 days at 50 mg/kg or 100 mg/kg. The current study demonstrates a new class of lead antibiotics, in the form of common fungal sterols, for antitrypanosomal drug development.