Stimulated transport of adenosine, guanosine and hypoxanthine in Crithidia luciliae: Metabolic machinery in which the parasite has a distinct advantage over the host

• Published in: International journal for parasitology Vol. 27; no. 2; pp. 241 - 249
• Main Authors: Gero, Annette M., Day, Rachel E., Hall, Simone T.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-02-1997
• Subjects: 3′nucleotidase/nuclease (3′NTase, EC 3.1.3.6), regulation by purines; Adenosine - metabolism; Aminoisobutyric Acids - metabolism; Animals; Biological Transport; Crithidia - growth & development; Crithidia - metabolism; Crithidia luciliae; Culture Media, Serum-Free; Cycloheximide - pharmacology; Deoxyglucose - metabolism; Guanosine - metabolism; Hypoxanthine - metabolism; Inosine Monophosphate - metabolism; metabolism; nucleoside transport; Nucleotidases - metabolism; Protein Synthesis Inhibitors - pharmacology; nucleoside transport; metabolism; 3′nucleotidase/nuclease (3′NTase, EC 3.1.3.6), regulation by purines; Crithidia luciliae
• ISSN: 0020-7519; 1879-0135
• DOI: 10.1016/S0020-7519(96)00153-1

Nutritional insufficiency is a common environmental extreme to which parasitic protozoa are routinely exposed. In this study of purine salvage mechanisms we illustrate some successful adaptations of the parasite
Crithidia luciliae to its environment, particularly in the case of purine stress. In purine-depleted conditions, the insect trypanosome
C. luciliae has the ability to increase the rates of transport of adenosine, guanosine and hypoxanthine and the activity of the exoenzyme 3′nucleotidase (3′NTase) during the growth cycle. The dramatic increase in these activities appears after a 72-h period in culture. The increased activity of the purine transporters and 3′NTase could be suppressed by addition to the medium of a purine supplement such as adenosine or hypoxanthine (100 μM). Under conditions where the concentration of purines in the medium could be closely regulated,
C. luciliae grown in purine-replete medium (≥75 μM purine) exhibited low rates of purine transport and activity of 3′NTase. In comparison, parasites transferred to medium with a low purine source (≤7.5 μM adenosine) had levels of adenosine, guanosine and hypoxanthine transport elevated 25–40-fold. The results link the simultaneous increase in activity of the nucleoside and base transporters, 3′NTase activity and a general increase in the purine salvage of
C. luciliae to the concentration of purines available at any time to the parasite.