Trypanosoma brucei oleate desaturase. Its genetic and chemical evaluation as a candidate drug target

ANDRÉS ALLOATTI; SHREEDHARA GUPTA; MELISA GUALDRÓN-LÓPEZ; MARIANA IGOILLO-ESTEVE; PAUL A. NGUEWA; GLADYS DEUMER; PIERRE WALLEMACQ; SILVIA G. ALTABE; PAUL A. M. MICHELS; ANTONIO D. UTTARO

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2010

1932-6203

ESTE TRABAJO HA SIDO ACEPTADO CON CORRECCIONES EN:  PLOS ONE (JULIO DE 2010) Abstract Background: Trypanosomes can synthesize polyunsaturated fatty acids. Previously, we have shown that they possess oleate desaturase (OD) and stearoyl-CoA desaturase (SCD) to convert stearate (C18) into oleate (C18:1) and linoleate (C18:2), respectively. Here we examine if OD is essential to these parasites. Methodology: Cultured procyclic (insect-stage) form (PCF) and bloodstream-form (BSF) Trypanosoma brucei cells were treated with 12- and 13-thiastearic acid (12-TS and 13-TS), inhibitors of OD, and the expression of the enzyme was knocked down by RNA interference. The phenotype of these cells was studied Principal Findings: Growth of PCF T. brucei was totally inhibited by 100 ìM of 12-TS and 13-TS, with EC50 values of 40 ± 2 and 30 ± 2 ìM, respectively. The BSF was more sensitive, with EC50 values of 7 ± 3 and 2 ± 1 ìM, respectively. This growth phenotype was due to the inhibitory effect of thiastearates on OD and, to a lesser extent, on SCD. The enzyme inhibition caused a drop in total unsaturated fatty-acid level of the cells, with a slight increase in oleate but a drastic decrease in linoleate level, most probably affecting membrane fluidity. After knocking down OD expression in PCF, the linoleate content was notably reduced, whereas that of oleate drastically increased, maintaining a normal total unsaturated fatty-acid level. Interestingly, the growth phenotype of the RNAi-induced cells was similar to that found for thiastearate-treated trypanosomes, with the former cells growing twofold slower than the latter ones, indicating that the linoleate content itself and not only fluidity could be essential for normal membrane functionality. A similar deleterious effect was found after RNAi in BSF, even with a mere 8% reduction of OD activity, indicating that its full activity is essential. Conclusions/Significance: As OD is essential for trypanosomes and is not present in mammalian cells, it is a promising target for chemotherapy of African trypanosomiasis.