Trypanosoma brucei bloodstream forms express highly specific and separate transporters for adenine and hypoxanthine; evidence for a new protozoan purine transporter family?

Campagnaro, G. D., Alzahrani, K. J., Munday, J. C. and De Koning, H. P. (2018) Trypanosoma brucei bloodstream forms express highly specific and separate transporters for adenine and hypoxanthine; evidence for a new protozoan purine transporter family? Molecular and Biochemical Parasitology, 220, pp. 46-56. (doi:10.1016/j.molbiopara.2018.01.005) (PMID:29371154)

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Abstract

The transport of nucleobases and nucleosides in protozoan parasites is known to be performed by Equilibrative Nucleoside Transporter (ENT) family members, including the extensively studied P1 and P2 nucleoside transporters of T. brucei bloodstream forms. Studies with P2 knockout parasites suggested the existence of as yet uncharacterised purine transport mechanisms in these cells. Here, we deleted several ENT genes, in addition to P2, including an array comprising three genes encoding for high-affinity broad-selectivity nucleobase transporters - the longest multi-gene locus deletion in T. brucei to date. It was verified that none of them appreciably contributed to the transport of hypoxanthine in bloodstream forms grown axenically in HMI-9 medium, which was mainly performed by a previously not described hypoxanthine-specific transporter (HXT1) with a Km of 22 ± 1.7 μM and Vmax of 0.49 ± 0.06 pmol(107 cells)-1s-1. The uptake of adenine was also assessed in the knockout cells and was performed by a highly specific adenine transporter (ADET1) with a Km of 573 ± 62 nM and Vmax of 0.23 ± 0.06 pmol(107 cells)-1 s-1. Neither HXT1 nor ADET1 displayed any affinity for other natural purines or pyrimidines and could not be completely inhibited by hypoxanthine or adenine analogues. These carriers may be the final pieces in the substantial transporter array trypanosomes can employ to fine-tune the uptake of purines from diverse environments during their life cycles, and may be encoded by genes other than those of the ENT family.

Item Type:Articles
Additional Information:GDC is funded by a PhD scholarship from Science Without Borders (206385/2014-5, CNPq, Brazil). KJA is funded by a studentship from Taif University, Taif, Saudi Arabia.
Keywords:ENT family, Trypanosoma brucei, adenine, hypoxanthine, nucleobase uptake.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Munday, Dr Jane and Campagnaro, Gustavo and Alzahrani, Khalid Jamaan and De Koning, Professor Harry
Authors: Campagnaro, G. D., Alzahrani, K. J., Munday, J. C., and De Koning, H. P.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Molecular and Biochemical Parasitology
Publisher:Elsevier
ISSN:0166-6851
ISSN (Online):1872-9428
Published Online:31 January 2018
Copyright Holders:Copyright © 2018 Elsevier B.V.
First Published:First published in Molecular and Biochemical Parasitology 220: 46-56
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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