The heat shock protein HSP70 and heat shock cognate protein HSC70 contribute to antimony tolerance in the protozoan parasite Leishmania

Abstract

Antimony-containing drugs are still the drugs of choice in the treatment of infections caused by the parasite Leishmania. Resistance to antimony is now common in some parts of the world, and several mechanisms of resistance have been described. By transfecting cosmid banks and selecting with potassium antimonyl tartrate (SbIII), we have isolated a cosmid associated with resistance. This cosmid contains 2 copies of the heat shock protein 70 (HSP70) and 1 copy of the heat shock cognate protein 70 (HSC70). Several data linked HSP70 to antimony response and resistance. First, several Leishmania species, both as promastigotes and amastigotes, increased the expression of their HSP70 proteins when grown in the presence of 1 or 2 times the Effect Concentration 50% of SbIII. In several mutants selected for resistance to either SbIII or to the related metal arsenite, the HSP70 proteins were found to be overexpressed. This increase was also observed in revertant cells grown for several passages in the absence of SbIII, suggesting that this increased production of HSP70 is stable. Transfection of HSP70 or HSC70 in Leishmania cells does not confer resistance directly, though these transfectants were better able to tolerate a shock with SbIII. Our results are consistent with HSP70 and HSC70 being a first line of defense against SbIII until more specific and efficient resistance mechanisms take over.

A Proteomics Screen Implicates HSP83 and a Small Kinetoplastid Calpain-related Protein in Drug Resistance in Leishmania donovani Clinical Field Isolates by Modulating Drug-induced Programmed Cell Death

“…allowing the cell to develop more specific and efficient resistance mechanisms against Sb(III) (58).…”

“…Indeed several HSPs were overexpressed in the resistant strain 9518, and the protein most down-regulated in strain 9518 was SKCRP14.1 (Table II). Two HSPs were increased, HSP70 and HSP83 (Table II), but the (minor) role of HSP70 in Sb(III) tolerance has already been established in Leishmania (58). The genes coding for HSP83, SKCRP14.1, and 14-3-3 were cloned into the Leishmania Psp␣NEO␣ vector.…”

Differential Protein Expression Analysis of Leishmania major Reveals Novel Roles for Methionine Adenosyltransferase and S-Adenosylmethionine in Methotrexate Resistance

“…Gels of proteins extracted from these mutants grown in the absence of MTX for several rounds show that some of these spots are decreased although not down to wild type levels. 2 In one study, some heat shock proteins remain overexpressed in cells completely adapted to trivalent antimony and grown for numerous passages in the absence of any obvious stress (34). It is, thus, possible that remnants of the stress response expressed during drug selection remain in adapted, resistant mutants or that resistant cells are under continuous stress.…”

A Telomeric Cluster of Antimony Resistance Genes on Chromosome 34 of Leishmania infantum

“…Enzymes such as trypanothione synthetase (L. major F27.1870) and trypanothione reductase (L. major F05.0350) are also part of the exosome load and involved in antimony metabolism. In addition to this, two heat shock proteins that have been associated with antimony resistance, HSP90 (57) and HSP70 (58), are also prominent in exosomes. Whether the exosomal transport of these proteins is functionally related to their role as antimony resistance markers is a question that remains to be solved.…”