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Changes in adenosine transport associated with melaminophenyl arsenical (Mel CY) resistance in Trypanosoma evansi: down-regulation and affinity changes of the P2 transporter

Published online by Cambridge University Press:  05 December 2003

E. A. SUSWAM ,
C. A. ROSS  and
R. J. MARTIN
E. A. SUSWAM
Affiliation:
Center for Tropical Veterinary Medicine, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK Present address: Department of Neurology, University of Alabama at Birmingham, 1066 THT, 1900 University Boulevard, Birmingham, AL 35294, USA.
C. A. ROSS
Affiliation:
Center for Tropical Veterinary Medicine, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK
R. J. MARTIN
Affiliation:
Department of Biomedical Sciences, Iowa State University, Ames Iowa, IA 50011, USA
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Abstract

Studies of the kinetics of adenosine transport were carried out on the P1 and P2 transporters of drug-sensitive Trypanosoma evansi and its cloned derivative, resistant to the melaminophenyl arsenical Mel CY. Characterization of adenosine uptake was made by estimation of the maximum concentration taken up at time infinity (Amax). Amax on the P2 transporter of sensitive T. evansi was greater than Amax on the P1 transporter. Amax of the P2 transporter was significantly decreased in drug-resistant trypanosomes. The effect of adenosine concentration and inhibitors, on the rate of adenosine uptake, was described by Michaelis-Menten equations. In sensitive T. evansi, the maximum velocity of adenosine uptake (Vmax) of the P2 transporter was 2-fold greater than Vmax of the P1 transporter. The Vmax of the P2 transporter in resistant parasites was reduced 9-fold. The binding constants Km and Ki on the P2 transporter of resistant T. evansi, showed that resistance was associated with an increased affinity for adenosine, and a decreased affinity for adenine and Berenil. We suggest that resistance to melaminophenyl arsenicals in T. evansi, occurs via 2 mechanisms: (1) a reduction in the number of expressed P2 transporter molecules resulting in decreased uptake of melaminophenyl arsenicals; (2) a change in the binding properties of the P2 transporter.

Keywords

P2 transportersdown-regulationaffinity changesTrypanosoma evansi
Type
Research Article
Information
Parasitology , Volume 127 , Issue 6 , December 2003 , pp. 543 - 549
Copyright
2003 Cambridge University Press

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References

REFERENCES

BARRETT, M. P., ZHANG, Z. Q., DENISE, H., GIROUD, C. & BALTZ, T. ( 1995). A diamidine-resistant Trypanosoma equiperdum clone contains a P2 purine transporter with reduced substrate affinity. Molecular and Biochemical Parasitology 73, 223–229.CrossRefGoogle Scholar
CARTER, N. S., BERGER, B. J. & FAIRLAMB, A. H. ( 1995). Uptake of diamidine drugs by the P2 nucleoside transporter in melarsen-sensitive and resistant Trypanososma brucei brucei. The Journal of Biological Chemistry 270, 28153– 28157.Google Scholar
CARTER, N. S. & FAIRLAMB, A. ( 1993). Arsenical-resistant trypanosomes lack an unusual adenosine transporter. Nature, London 361, 173–175.CrossRefGoogle Scholar
GIBALDI, M. ( 1991). Biopharmaceutics and Clinical Pharaceutics, 4th Edn. Lea and Febiger. London.
de KONING, H. P. & JARVIS, S. M. ( 1997). Purine nucleobase transport in bloodstream forms of Trypanosoma brucei is mediated by two novel transporters. Molecular and Biochemical Parasitology 89, 245–258.CrossRefGoogle Scholar
de KONING, H. P. & JARVIS, S. M. ( 1998). A highly selective, high-affinity transporter for uracil for Trypanosoma brucei brucei: evidence for proton-dependent transport. Biochemical and Cell Biology 76, 853–858.CrossRefGoogle Scholar
de KONING, H. P. & JARVIS, S. M. ( 1999). Adenosine transporters in bloodstream forms of Trypanosoma brucei brucei: Substrate recognition motifs and affinity for trypanocidal drugs. Molecular Pharmacology 56, 1162–1170.CrossRefGoogle Scholar
de KONING, H. P., WATSON, C. J. & JARVIS, S. M. ( 1998). Characterization of a nucleoside/proton symporter in procyclic Trypanosoma brucei brucei. The Journal of Biological Chemistry 273, 9486–9494.CrossRefGoogle Scholar
de KONING, H. P., WATSON, C. J., SUTCLIFF, L. & JARVIS, S. M. ( 2000). Differential regulation of nucleoside and nucleobase transporters in Crithidia fasciculata and Trypanosoma brucei brucei. Molecular and Biochemical Parasitology 106, 93–107.CrossRefGoogle Scholar
FAIRLAMB, A. H., CARTER, N. S., CUNNINGHAM, M. & SMITH, K. ( 1992). Characterisation of melarsen-resistant Trypanosoma brucei brucei with respect to cross-resistance to other drugs and trypanothione metabolism. Molecular and Biochemical Parasitology 53, 213–222.CrossRefGoogle Scholar
MASER, P., SUTERLING, C., KRALLI, A. & KAMINSKY, R. ( 1999). A nucleoside transporter from Trypanosoma brucei involved in drug resistance. Science 285, 242–244.Google Scholar
ROSS, C. A. & BARNS, A. M. ( 1996). Alteration to one of three adenosine transporters is associated with resistance to Cymelarsan in Tryanosoma evansi. Parasitology Research 82, 183–188.CrossRefGoogle Scholar
SANCHEZ, M. A., TRYON, R., GREEN, J., BOOR, I. & LANDFEARS, S. M. ( 2002). Six related nucleoside/nucleobase transporters from Trypanosoma brucei exhibit distinct biochemical functions. The Journal of Biological Chemistry 277, 21499–21504.CrossRefGoogle Scholar
SCOTT, A. G., TAIT, A. & TURNER, C. M. R. ( 1997). Trypanosoma brucei: lack of cross-resistance to melarsoprol in vitro by Cymelarsan-resistant parasites. Experimental Parasitology 86, 181–190.CrossRefGoogle Scholar
SUSWAM, E. A., TAYLOR, D. W., ROSS, C. A. & MARTIN, R. J. ( 2001). Changes in properties of adenosine transporters in Trypanosoma evansi and modes of selection of resistance to the melaminophenyl arsenical drug, Mel Cy. Veterinary Parasitology 102, 193–208.CrossRefGoogle Scholar