Emetine-resistant mutants of Entamoeba histolytica overexpress mRNAs for multidrug resistance.
We report here the identification of multiple 344-bp segments of amoeba DNA similar to the human multidrug resistance (mdr) gene using primers to conserved regions of the P-glycoprotein and the polymerase chain reaction (PCR). The amino acid sequences of amoeba mdr-like PCR products were 46-97% identical to each other, 46-51% identical to human mdr1 sequences, and 30-35% identical with Plasmodium falciparum mdr-like sequences. On Northern blots, the mdr-like PCR products identified amoeba mRNAs 4.5-5 kb long, similar to the 5-kb mRNAs reported for the mammalian mdr gene. These mdr-like mRNAs were increased at least 7 times in emetine-resistant mutant clone C2 amoebae vs. wild-type clone A parasites. Furthermore, the expression of the mdr-like mRNAs was increased 3-4 times when clone C2 mutants were grown under drug pressure vs. the same parasites grown without emetine. In contrast, the number of genomic copies of the mdr-like DNA segments was not increased in the mutant clone C2 vs. the wild-type clone A amoebae, and no rearrangements of the mdr-like DNA segments by the mutant were identified on Southern blots. In conclusion, there appears to be a family of mdr-like genes in Entamoeba histolytica, which may be involved in drug resistance by the parasite because they are overexpressed in drug-resistant mutants.[1]References
- Emetine-resistant mutants of Entamoeba histolytica overexpress mRNAs for multidrug resistance. Samuelson, J., Ayala, P., Orozco, E., Wirth, D. Mol. Biochem. Parasitol. (1990) [Pubmed]
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