Mapping the transporter-substrate interactions of the Trypanosoma cruzi NB1 nucleobase transporter reveals the basis for its high affinity and selectivity for hypoxanthine and guanine and lack of nucleoside uptake

Aldfer, M. M. , Hulpia, F., van Calenbergh, S. and De Koning, H. P. (2024) Mapping the transporter-substrate interactions of the Trypanosoma cruzi NB1 nucleobase transporter reveals the basis for its high affinity and selectivity for hypoxanthine and guanine and lack of nucleoside uptake. Molecular and Biochemical Parasitology, 258, 111616. (doi: 10.1016/j.molbiopara.2024.111616) (PMID:38401850)

Abstract

Trypanosoma cruzi is a protozoan parasite and the etiological agent of Chagas disease, a debilitating and sometimes fatal disease that continues to spread to new areas. Yet, Chagas disease is still only treated with two related nitro compounds that are insufficiently effective and cause severe side effects. Nucleotide metabolism is one of the known vulnerabilities of T. cruzi, as they are auxotrophic for purines, and nucleoside analogues have been shown to have genuine promise against this parasite in vitro and in vivo. Since purine antimetabolites require efficient uptake through transporters, we here report a detailed characterisation of the T. cruzi NB1 nucleobase transporter with the aim of elucidating the interactions between TcrNB1 and its substrates and finding the positions that can be altered in the design of novel antimetabolites without losing transportability. Systematically determining the inhibition constants (Ki) of purine analogues for TcrNB1 yielded their Gibbs free energy of interaction, ΔG0. Pairwise comparisons of substrate (hypoxanthine, guanine, adenine) and analogues allowed us to determine that optimal binding affinity by TcrNB1 requires interactions with all four nitrogen residues of the purine ring, with N1 and N9, in protonation state, functioning as presumed hydrogen bond donors and unprotonated N3 and N7 as hydrogen bond acceptors. This is the same interaction pattern as we previously described for the main nucleobase transporters of Trypanosoma brucei spp. and Leishmania major and makes it the first of the ENT-family genes that is functionally as well as genetically conserved between the three main kinetoplast pathogens.

• Item Type: Articles
• Additional Information: MAA was supported by a PhD studentship from the Libyan government and FH was supported by a PhD-scholarship from FWO-Flanders. The work at the University of Ghent was further supported by project G013118N of the FWO.
• Keywords: Trypanosoma cruzi, nucleobase transporter, allopurinol, TcrNB1, hypoxanthine uptake, kinetoplastid parasite.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Aldfer, Mustafa Mohamed and De Koning, Professor Harry

Creator Roles

De Koning, H. P.: Writing – review and editing, Writing – original draft, Validation, Supervision, Data curation, Conceptualization
Aldfer, M. M.: Writing – original draft, Investigation

• Authors: Aldfer, M. M., Hulpia, F., van Calenbergh, S., and De Koning, H. P.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: Molecular and Biochemical Parasitology
• Publisher: Elsevier
• ISSN: 0166-6851
• ISSN (Online): 1872-9428
• Published Online: 23 February 2024
• Copyright Holders: Copyright © 2024 The Authors
• First Published: First published in Molecular and Biochemical Parasitology 258: 111616
• Publisher Policy: Reproduced under a Creative Commons License