title: Genetic validation of aminoacyl-tRNA synthetases as drug targets in Trypanosoma brucei.
abstract: Human African trypanosomiasis (HAT) is an important public health threat in sub-Saharan Africa. Current drugs are unsatisfactory, and new drugs are being sought. Few validated enzyme targets are available to support drug discovery efforts, so our goal was to obtain essentiality data on genes with proven utility as drug targets. Aminoacyl-tRNA synthetases (aaRSs) are known drug targets for bacterial and fungal pathogens and are required for protein synthesis. Here we survey the essentiality of eight Trypanosoma brucei aaRSs by RNA interference (RNAi) gene expression knockdown, covering an enzyme from each major aaRS class: valyl-tRNA synthetase (ValRS) (class Ia), tryptophanyl-tRNA synthetase (TrpRS-1) (class Ib), arginyl-tRNA synthetase (ArgRS) (class Ic), glutamyl-tRNA synthetase (GluRS) (class 1c), threonyl-tRNA synthetase (ThrRS) (class IIa), asparaginyl-tRNA synthetase (AsnRS) (class IIb), and phenylalanyl-tRNA synthetase (α and β) (PheRS) (class IIc). Knockdown of mRNA encoding these enzymes in T. brucei mammalian stage parasites showed that all were essential for parasite growth and survival in vitro. The reduced expression resulted in growth, morphological, cell cycle, and DNA content abnormalities. ThrRS was characterized in greater detail, showing that the purified recombinant enzyme displayed ThrRS activity and that the protein localized to both the cytosol and mitochondrion. Borrelidin, a known inhibitor of ThrRS, was an inhibitor of T. brucei ThrRS and showed antitrypanosomal activity. The data show that aaRSs are essential for T. brucei survival and are likely to be excellent targets for drug discovery efforts.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Savitha
authors.initials: S
authors.lastname: Kalidas
authors.forename: Igor
authors.initials: I
authors.lastname: Cestari
authors.forename: Severine
authors.initials: S
authors.lastname: Monnerat
authors.forename: Qiong
authors.initials: Q
authors.lastname: Li
authors.forename: Sandesh
authors.initials: S
authors.lastname: Regmi
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hasle
authors.forename: Mehdi
authors.initials: M
authors.lastname: Labaied
authors.forename: Marilyn
authors.initials: M
authors.lastname: Parsons
authors.forename: Kenneth
authors.initials: K
authors.lastname: Stuart
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Phillips
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D055808:Drug Discovery; D005233:Fatty Alcohols / Q000494:pharmacology; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014344:Trypanocidal Agents / Q000494:pharmacology*; D014346:Trypanosoma brucei brucei / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics
chemical_list: D005233:Fatty Alcohols; D015800:Protozoan Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014344:Trypanocidal Agents; C005066:borrelidin; D000604:Amino Acyl-tRNA Synthetases