Effect of proteasome inhibitors on the growth, encystation, and excystation of Entamoeba histolytica and Entamoeba invadens

Abstract

The effect of three proteasome inhibitors, lactacystin, clasto-lactacystin beta-lactone, and MG-132, on the growth, encystation, and excystation of Entamoeba histolytica and Entamoeba invadens was examined. All of these drugs blocked E. histolytica growth in a concentration-dependent manner; lactacystin was most potent for the inhibition and MG-132 showed the inhibitory effect only at higher concentrations. E. invadens was more resistant to these drugs than E. histolytica. Encystation of E. invadens was also inhibited and was more sensitive to the drugs than was growth. Beta-lactone was the most potent encystation inhibitor. The inhibitory effect of lactacystin and the beta-lactone on encystation was slightly and little abrogated by the removal of the drug, respectively. Multinucleation occurred in E. histolytica trophozoites treated with these drugs, being most marked with lactacystin. In contrast, no multinucleation was observed in E. invadens treated with the drugs. Electron microscopy revealed that the treatment of E. histolytica trophozoites with lactacystin led to an increase in the number of cells with many glycogen granules in the cytoplasm. Lactacystin, beta-lactone and MG-132 had no or little effect on the excystation and metacystic development of E. invadens. These results suggest that proteasome function plays an important role for Entamoeba growth and encystation, but has no obvious effect on excystation or metacystic development.

Antileishmanial activity of HIV protease inhibitors

“…They are characterised by evolutionarily conserved proteins and are present in Trypanosoma brucei [8], Trypanosoma cruzi [9], Toxoplasma gondii [10], Plasmodium spp. [11], Entamoeba histolytica and Entamoeba invadens [12], as well as in Leishmania mexicana [13]. A molecular similarity was found between the human 20S proteasome ␣-type subunit and a Leishmania donovani cDNA clone [14] and between a gene encoding a 20S proteasome ␤ subunit in Plasmodium falciparum [15].…”

Structural Determinants of Ubiquitin Conjugation in Entamoeba histolytica

“…Of particular feasibility may be a proteasome inhibitor with selectivity for the E. histolytica protein target, given the previously demonstrated effects of proteasome inhibition on trophozoite proliferation and encystation (16). Alternatively, EhUba1-specific E1 inhibition may be expected to grossly perturb trophozoite function and viability, given the necessity of ubiquitin activation for multiple vital cellular processes in other eukaryotes (38).…”

“…However, functional studies of this putative ubiquitination machinery have not yet emerged. Interestingly, treatment with proteasome inhibitors impairs growth of E. histolytica trophozoites and encystation in the related species Entamoeba invadens, suggesting that the ubiquitin-proteasome pathway may be a valuable therapeutic target (16). Altered expression of ubiquitin-proteasomal genes has also been correlated with perturbations in virulence (e.g.…”

Effect of artificial gastrointestinal fluids on the excystation and metacystic development of Entamoeba invadens

“…Metacystic development is the process in which a hatched metacystic amoeba with four nuclei divides to produce eight amoebulae, which grow to become trophozoites (Dobell 1928;Cleveland and Sanders 1930;Geiman and Ratcliffe 1936). The transfer of E. invadens cysts in an encystation medium to a growth medium induces in vitro excystation (McConnachie 1955;Rengpien and Bailey 1975;Garcia-Zapien et al 1995;Makioka et al 2002). Before excystation in the ileum, cysts are exposed to gastric fluid and then intestinal fluid during passage through the stomach and intestine.…”