Trypanosoma brucei methylthioadenosine phosphorylase protects the parasite from the antitrypanosomal effect of deoxyadenosine

Vodnala, M., Ranjbarian, F., Pavlova, A., de Koning, H. P. and Hofer, A. (2016) Trypanosoma brucei methylthioadenosine phosphorylase protects the parasite from the antitrypanosomal effect of deoxyadenosine. Journal of Biological Chemistry, 291(22), pp. 11717-11726. (doi: 10.1074/jbc.M116.715615) (PMID:27036940) (PMCID:PMC4882440)

Abstract

Trypanosoma brucei causes African sleeping sickness for which no vaccine exists and available treatments are of limited use due to their high toxicity or lack of efficacy. T. brucei cultivated in the presence of deoxyadenosine accumulates high levels of dATP in an adenosine kinase-dependent process and dies within a few hours. Here we show that T. brucei treated with 1 mM deoxyadenosine accumulates higher dATP levels than mammalian cells but that this effect diminishes quickly as the concentration of the deoxynucleoside decreases. Radioactive tracer studies showed that the parasites are partially protected against lower concentrations of deoxyadenosine by the ability to cleave it and use the adenine for ATP synthesis. T. brucei methylthioadenosine phosphorylase (TbMTAP) was found to be responsible for the cleavage as indicated by the phosphate dependence of deoxyadenosine cleavage in T. brucei cell extracts and increased deoxyadenosine sensitivity in TbMTAP knockdown cells. Recombinant TbMTAP exhibited higher turnover number (kcat) and Km values for deoxyadenosine than for the regular substrate, methylthioadenosine. One of the reaction products, adenine, inhibited the enzyme, which might explain why TbMTAP-mediated protection is less efficient at higher deoxyadenosine concentrations. Consequently, T. brucei grown in the presence of adenine demonstrated increased sensitivity to deoxyadenosine. For deoxyadenosine/adenosine analogues to remain intact and be active against the parasite, they need to either be resistant to TbMTAP-mediated cleavage, which is the case with the three known antitrypanosomal agents adenine arabinoside, tubercidin, and cordycepin, or they need to be combined with TbMTAP inhibitors.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: De Koning, Professor Harry
• Authors: Vodnala, M., Ranjbarian, F., Pavlova, A., de Koning, H. P., and Hofer, A.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: Journal of Biological Chemistry
• Publisher: American Society for Biochemistry and Molecular Biology
• ISSN: 0021-9258
• ISSN (Online): 1083-351X
• Published Online: 01 April 2016
• Copyright Holders: Copyright © 2016 The American Society for Biochemistry and Molecular Biology, Inc.
• First Published: First published in Journal of Biological Chemistry 291(22): 11717-11726
• Publisher Policy: Reproduced in accordance with the publisher copyright policy