Knockdown of asparagine synthetase A renders trypanosoma brucei auxotrophic to asparagine
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 eit...
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| Main Authors: | , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
December 5, 2013
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| In: |
PLoS neglected tropical diseases
Year: 2013, Volume: 7, Issue: 12, Pages: 1-14 |
| ISSN: | 1935-2735 |
| DOI: | 10.1371/journal.pntd.0002578 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1371/journal.pntd.0002578 Verlag, lizenzpflichtig, Volltext: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002578 
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| Author Notes: | Inês Loureiro, Joana Faria, Christine Clayton, Sandra Macedo Ribeiro, Nilanjan Roy, Nuno Santarém, Joana Tavares, Anabela Cordeiro-da-Silva |
| Summary: | 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. |
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| Item Description: | Gesehen am 08.06.2021 |
| Physical Description: | Online Resource |
| ISSN: | 1935-2735 |
| DOI: | 10.1371/journal.pntd.0002578 |