Abstract:
Emergence of resistance to pentavalent antimonials has become a severe obstacle in treatment of visceral leishmaniasis (VL) in the Indian subcontinent. The mechanisms operating in laboratory generated strains are somewhat known, but the determinants of clinical antimony resistance are not well understood. By utilizing a DNA microarray expression profiling approach, we identified a gene encoding mitogen-activated protein kinase 1 (MAPK1) for the kinetoplast protozoan Leishmania donovani (LdMAPK1) that was consistently down-regulated in antimony-resistant field isolates. The expression level of the gene was validated by real time polymerase chain reaction). Furthermore, decreased expression of LdMAPK1 was also confirmed at the protein level in resistant isolates. Primary structure analysis of LdMAPK1 revealed the presence of all characteristic features of MAPK1. When expressed in E. coli, the recombinant enzyme showed kinase activity with myelin basic protein as substrate and was inhibited by staurosporine. Interestingly, over expression of this gene in a drug sensitive laboratory strain and resistant field isolate resulted in increase in sensitivity of the transfectants towards Sb (III), suggesting its role in antimony resistance. Our results demonstrate that down regulation of LdMAPK1 may be in part correlated with the antimony drug resistance in Indian VL isolates.
