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Adaptive responses to purine starvation in Leishmania donovani
Author(s) -
Carter Nicola S.,
Yates Phillip A.,
Gessford Sarah K.,
Galagan Sean R.,
Landfear Scott M.,
Ullman Buddy
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07327.x
Subject(s) - purine , biology , nucleoside transporter , nucleotide salvage , nucleoside , purine nucleoside phosphorylase , biochemistry , purine metabolism , transporter , enzyme , nucleotide , gene
Summary Starvation of Leishmania donovani parasites for purines leads to a rapid amplification in purine nucleobase and nucleoside transport. Studies with nucleoside transport‐deficient L. donovani indicate that this phenomenon is mediated by the nucleoside transporters LdNT1 and LdNT2, as well as by the purine nucleobase transporter LdNT3. The escalation in nucleoside transport cannot be ascribed to an increase in either LdNT1 or LdNT2 mRNA. However, Western analyses on parasites expressing epitope‐tagged LdNT2 revealed a marked upregulation in transporter protein at the cell surface. Kinetic investigations of LdNT1 and LdNT2 activities from purine‐replete and purine‐starved cells indicated that both transporters exhibited significant increases in V max for their ligands under conditions of purine‐depletion, although neither transporter displayed an altered affinity for its respective ligands. Concomitant with the increase in purine nucleoside and nucleobase transport, the purine salvage enzymes HGPRT, XPRT and APRT were also upregulated, suggesting that under conditions where purines are limiting, Leishmania parasites remodel their purine metabolic pathway to maximize salvage. Moreover, qRT‐PCR analyses coupled with cycloheximide inhibition studies suggest that the underlying molecular mechanism for this augmentation in purine salvage occurs post‐transcriptionally and is reliant on de novo protein synthesis.