Physiology and molecular biology of multidrug resistance in Entamoeba histolytica

RESUMO

In this paper, we present the most relevant facts on multidrug resistance (MDR) in the protozoan parasite Entamoeba histolytica. MDR in E. histolytica presents characteristics similar to transformed mammalian cells. E. histolytica drug resistant mutants show cross-resistance to several drugs, and as in mammalian cells the resistance is reverted by verapamil. Six P-glycoprotein-like genes (EhPgp) have been cloned and characterized. Apparently, four of thses genes are transcribed in drug-resistance mutants (EhPgh1, EhPgp2, EhPgp5 and EhPgp6), although only Egpgp1, EhPgp5 and EhPgp6 transcripts were clearly detected. The open reading frame (ORF) of the four completely full length genes is about 1300 amino acids long. EhPgp1, EhPgp2 and EhPgp5 have between 64 and 67 percent of positional identity among them, while EhPgp6 shows 38 to 46 percent positional identity to the other ameba genes. Insterestingly, the phylogenetic tree suggested that Entamoeba P-glycoproteins are more related to the human and mouse P-glycoproteins. Differential gene expression in drug-resistant mutants was detected when specific probes for each EhPgp gene were used. To understand the differential expression of EhPgp genes we initiated the characterization of the upstream flanking regions of EhPgp1 and EhPgp5 genes. Upstream sequences showed between 53 and 66 percent of positional identity to Dictyostelium discoideum promoters