PHYSIOLOGY AND MOLECULAR-BIOLOGY OF MULTIDRUG-RESISTANCE IN ENTAMOEBA-HISTOLYTICA

In this paper, we present the most relevant facts on multidrug resista nce (MDR) in the protozoan parasite Entamoeba histolytica. MDR in E. h istolytica presents characteristics similar to transformed mammalian c ells. E. histolytica drug resistant mutants show cross-resistance to s everal 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 these genes are transcribed in drug -resistant mutants (EhPgp1, EhPgp2, EhPgp5 and EhPgp6), although only EhPgp1, 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 6 7% of positional identity among them, while EhPgp6 shows 38 to 46% pos itional identity to the other ameba genes. Interestingly, the phylogen etic tree suggested that Entamoeba P-glycoproteins are more related to the human and mouse P-glycoproteins than to the Plasmodium and Leishm ania P-glycoproteins, Differential gene expression in drug-resistant m utants was detected when specific probes for each Ehpgp gene were used . To understand the differential expression of EhPgp genes we initiate d the characterization of the upstream flanking regions of EhPgp1 and EhPgp5 genes. Upstream sequences showed between 53 and 66% of position al identity to Dictyostelium discoideum promoters.