Pathogens (Oct 2022)

<i>Trypanosoma brucei</i> Acyl-Protein Thioesterase-like (TbAPT-L) Is a Lipase with Esterase Activity for Short and Medium-Chain Fatty Acids but Has No Depalmitoylation Activity

  • Robert W. B. Brown,
  • Aabha I. Sharma,
  • Miguel Rey Villanueva,
  • Xiaomo Li,
  • Ouma Onguka,
  • Leeor Zilbermintz,
  • Helen Nguyen,
  • Ben A. Falk,
  • Cheryl L. Olson,
  • Joann M. Taylor,
  • Conrad L. Epting,
  • Rahul S. Kathayat,
  • Neri Amara,
  • Bryan C. Dickinson,
  • Matthew Bogyo,
  • David M. Engman

DOI
https://doi.org/10.3390/pathogens11111245
Journal volume & issue
Vol. 11, no. 11
p. 1245

Abstract

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Dynamic post-translational modifications allow the rapid, specific, and tunable regulation of protein functions in eukaryotic cells. S-acylation is the only reversible lipid modification of proteins, in which a fatty acid, usually palmitate, is covalently attached to a cysteine residue of a protein by a zDHHC palmitoyl acyltransferase enzyme. Depalmitoylation is required for acylation homeostasis and is catalyzed by an enzyme from the alpha/beta hydrolase family of proteins usually acyl-protein thioesterase (APT1). The enzyme responsible for depalmitoylation in Trypanosoma brucei parasites is currently unknown. We demonstrate depalmitoylation activity in live bloodstream and procyclic form trypanosomes sensitive to dose-dependent inhibition with the depalmitoylation inhibitor, palmostatin B. We identified a homologue of human APT1 in Trypanosoma brucei which we named TbAPT-like (TbAPT-L). Epitope-tagging of TbAPT-L at N- and C- termini indicated a cytoplasmic localization. Knockdown or over-expression of TbAPT-L in bloodstream forms led to robust changes in TbAPT-L mRNA and protein expression but had no effect on parasite growth in vitro, or cellular depalmitoylation activity. Esterase activity in cell lysates was also unchanged when TbAPT-L was modulated. Unexpectedly, recombinant TbAPT-L possesses esterase activity with specificity for short- and medium-chain fatty acid substrates, leading to the conclusion, TbAPT-L is a lipase, not a depalmitoylase.

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