Modulation of Leishmania ABC Protein Gene Expression through Life Stages and among Drug-Resistant Parasites

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Abstract
The ATP-binding cassette (ABC) protein superfamily is one of the largest evolutionarily conserved families and is found in all kingdoms of life. The recent completion of the Leishmania genome sequence allowed us to analyze and classify its encoded ABC proteins. The complete sequence predicts a data set of 42 open reading frames (ORFs) coding for proteins belonging to the ABC superfamily, with representative members of every major subfamily (from ABCA to ABCH) commonly found in eukaryotes. Comparative analysis showed that the same ABC data set is found between Leishmania major and Leishmania infantum and that some orthologues are found in the genome of the related parasites Trypanosoma brucei and Trypanosoma cruzi . Customized DNA microarrays were made to assess ABC gene expression profiling throughout the two main Leishmania life stages. Two ABC genes ( ABCA3 and ABCG3 ) are preferentially expressed in the amastigote stage, whereas one ABC gene ( ABCF3 ) is more abundantly expressed in promastigotes. Microarray-based expression profiling experiments also revealed that three ABC genes ( ABCA3 , ABCC3 , and ABCH1 ) are overexpressed in two independent antimony-resistant strains compared to the parental sensitive strain. All microarray results were confirmed by real-time reverse transcription-PCR assays. The present study provides a thorough phylogenic classification of the Leishmania ABC proteins and sets the basis for further functional studies on this important class of proteins.