Discovery of an ergosterol-signaling factor that regulates Trypanosoma brucei growth

William Nes, Brad A. Haubrich, Ujjal K. Singha, Matthew B. Miller, Craigen R. Nes, Hosanna Anyatonwu, Laurence Lecordier, Presheet Patkar, David J. Leaver, Fernando Villalta, Benoit Vanhollebeke, Minu Chaudhuri

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20 Scopus citations


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.

Original languageEnglish
Pages (from-to)331-341
Number of pages11
JournalJournal of Lipid Research
Issue number2
StatePublished - Feb 1 2015


  • Anti-parasite drugs
  • Cholesterol
  • Ergosterol biosynthesis
  • Inhibitor
  • Knockdown
  • Ribonucleic acid interference
  • Sparking function


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