Details

Autor(en) / Beteiligte

• Mukhopadhyay, Rita
• Dey, Saibal
• Xu, Naxing
• Gage, Douglas
• Lightbody, James
• Ouellette, Marc
• Rosen, Barry P.

Titel

Trypanothione Overproduction and Resistance to Antimonials and Arsenicals in Leishmania

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 1996-09, Vol.93 (19), p.10383-10387

Ort / Verlag

United States: National Academy of Sciences of the United States of America

Erscheinungsjahr

1996

Quelle

MEDLINE

Beschreibungen/Notizen

• Leishmania resistant to arsenicals and antimonials extrude arsenite. Previous results of arsenite uptake into plasma membrane-enriched vesicles suggested that the transported species is a thiol adduct of arsenite. In this paper, we demonstrate that promastigotes of arsenite-resistant Leishmania tarentolae have increased levels of intracellular thiols. High-pressure liquid chromatography of the total thiols showed that a single peak of material was elevated almost 40-fold. The major species in this peak was identified by matrix-assisted laser desorption/ionization mass spectrometry as N$^{1}$,N$^{8}$-bis-(glutathionyl)spermidine (trypanothione). The trypanothione adduct of arsenite was effectively transported by the As-thiol pump. No difference in pump activity was observed in wild type and mutants. A model for drug resistance is proposed in which Sb(V)/As(V)-containing compounds, including the antileishmanial drug Pentostam, are reduced intracellularly to Sb(III)/As(III), conjugated to trypanothione, and extruded by the As-thiol pump. The ratelimiting step in resistance is proposed to be formation of the metalloid-thiol pump substrates, so that increased synthesis of trypanothione produces resistance. Increased synthesis of the substrate rather than an increase in the number of pump molecules is a novel mechanism for drug resistance.