Knockdown of asparagine synthetase A renders trypanosoma brucei auxotrophic to asparagine

• Verfasst von: Loureiro, Ines [VerfasserIn]
• Verfasst von: Faria, Joana [VerfasserIn]
• Verfasst von: Clayton, Christine [VerfasserIn]
• Verfasst von: Ribeiro, Sandra Macedo [VerfasserIn]
• Verfasst von: Roy, Nilanjan [VerfasserIn]
• Verfasst von: Santarém, Nuno [VerfasserIn]
• Verfasst von: Tavares, Joana [VerfasserIn]
• Verfasst von: Cordeiro-da-Silva, Anabela [VerfasserIn]
• Titel: Knockdown of asparagine synthetase A renders trypanosoma brucei auxotrophic to asparagine
• Verf.angabe: Inês Loureiro, Joana Faria, Christine Clayton, Sandra Macedo Ribeiro, Nilanjan Roy, Nuno Santarém, Joana Tavares, Anabela Cordeiro-da-Silva
• E-Jahr: 2013
• Jahr: December 5, 2013
• Umfang: 14 S.
• Teil: volume:7
• Teil: year:2013
• Teil: number:12
• Teil: elocationid:e2578
• Teil: pages:1-14
• Teil: extent:14
• Fussnoten: Gesehen am 08.06.2021
• Titel Quelle: Enthalten in: Public Library of SciencePLoS neglected tropical diseases
• Ort Quelle: Lawrence, Kan. : PLoS, 2007
• Jahr Quelle: 2013
• Band/Heft Quelle: 7(2013), 12, Artikel-ID e2578, Seite 1-14
• ISSN Quelle: 1935-2735
• DOI: doi:10.1371/journal.pntd.0002578
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Ammonia
• Sach-SW: Asparagine
• Sach-SW: Glutamine
• Sach-SW: Parasitic diseases
• Sach-SW: RNA interference
• Sach-SW: Trypanosoma
• Sach-SW: Trypanosoma brucei gambiense
• Sach-SW: Trypanosoma cruzi
• K10plus-PPN: 1760029998

Abstract

Asparagine synthetase (AS) catalyzes the ATP-dependent conversion of aspartate into asparagine using ammonia or glutamine as nitrogen source. There are two distinct types of AS, asparagine synthetase A (AS-A), known as strictly ammonia-dependent, and asparagine synthetase B (AS-B), which can use either ammonia or glutamine. The absence of AS-A in humans, and its presence in trypanosomes, suggested AS-A as a potential drug target that deserved further investigation. We report the presence of functional AS-A in Trypanosoma cruzi (TcAS-A) and Trypanosoma brucei (TbAS-A): the purified enzymes convert L-aspartate into L-asparagine in the presence of ATP, ammonia and Mg2+. TcAS-A and TbAS-A use preferentially ammonia as a nitrogen donor, but surprisingly, can also use glutamine, a characteristic so far never described for any AS-A. TbAS-A knockdown by RNAi didn't affect in vitro growth of bloodstream forms of the parasite. However, growth was significantly impaired when TbAS-A knockdown parasites were cultured in medium with reduced levels of asparagine. As expected, mice infections with induced and non-induced T. brucei RNAi clones were similar to those from wild-type parasites. However, when induced T. brucei RNAi clones were injected in mice undergoing asparaginase treatment, which depletes blood asparagine, the mice exhibited lower parasitemia and a prolonged survival in comparison to similarly-treated mice infected with control parasites. Our results show that TbAS-A can be important under in vivo conditions when asparagine is limiting, but is unlikely to be suitable as a drug target.