Phagocytosis and proteinase activity are not related to pathogenicity ofE. histolytica

Abstract

Tritiated dityrosine and isotrityrosine were detected by high performance liquid chromatography (HPLC) of acid hydrolysates of cuticular proteins from larval Ascaris suum following their 96-hr in vitro incubation in [3H]tyrosine. Sixty percent of the HPLC-recovered radiolabel was present as tyrosine, 20% as dityrosine, and 6% as isotrityrosine. Approximately 13% of radioactivity was associated with several unidentified peaks. A similar distribution of radioactivity was observed in acid hydrolysates of cuticular proteins from young adults of A. suum following 48 hr in vitro incubation with [3H]tyrosine. The 2-mercaptoethanol (2ME)-insoluble cuticular protein from the larval stages had a higher rate of synthesis of [3H]dityrosine than did the 2ME-soluble cuticular proteins, whereas the 2ME-soluble cuticular proteins had higher rates of synthesis of [3H]isotrityrosine. Pulse-chase studies of A. suum larvae demonstrated a relatively low rate of synthesis of both dityrosine and isotrityrosine. The addition to the culture media of the peroxidase inhibitors, phenylhydrazine (PHEN), 3-amino-1,2,4-triazole (AT), and N-acetyltyrosine (NAT) reduced the amount of [3H]tyrosine synthesized into both dityrosine and isotrityrosine. In a cell-free system, soluble extracts of A. suum larvae also converted radiolabeled tyrosine to dityrosine; isotrityrosine was produced by some extracts. The rate of conversion correlated with time of incubation and the volume of added extract and was inhibited by AT, NAT, and PHEN, with PHEN being the most potent inhibitor. The results of the present study suggest that the tyrosine residues of the cuticular proteins are posttranslationally modified by the formation of dityrosine and isotrityrosine cross-links. This modification is most likely mediated by a peroxidase.

Overexpression of Differentially Expressed Genes Identified in Non-pathogenic and Pathogenic Entamoeba histolytica Clones Allow Identification of New Pathogenicity Factors Involved in Amoebic Liver Abscess Formation

“…In contrast with most reports that described a correlation between erythrophagocytosis and ALA formation [22, 40–43], Monfort and colleagues and Tsutsumi and colleagues, as well as this study, did not confirm this correlation [21, 44]. In the present study, non-pathogenic clone B8 np showed the highest erythrophagocytosis rate, followed by clones A1 np and B2 p .…”

“…Such lack of correlation between CP activity levels and ALA formation was reported in only one other publication, where Montfort and colleagues also used pathogenic and non-pathogenic cultures of E . histolytica isolate HM-1:IMSS [21]. However, the missing correlation between CP activity and ALA formation is not necessarily inconsistent with previous results.…”

Entamoeba histolytica : a novel cysteine protease and an adhesin form the 112 kDa surface protein

“…Proteases have also been involved in E. histolytica virulence (Gadasi and Kessler, 1983; McKerrow, 1989; Keene et al ., 1990; Reed et al ., 1992; Tannich et al ., 1992). There is experimental evidence demonstrating a direct correlation between virulence and rate of phagocytosis and protease activity (Orozco et al ., 1985; Ankri et al ., 1998; 1999), but other reports contradict this assumption (Spice and Ackers, 1992; Montfort et al ., 1993).…”

Entamoeba histolytica: a novel cysteine protease and an adhesin form the 112 kDa surface protein

“…Proteases have also been involved in E. histolytica virulence (Gadasi and Kessler, 1983;McKerrow, 1989;Keene et al, 1990;Reed et al, 1992;Tannich et al, 1992). There is experimental evidence demonstrating a direct correlation between virulence and rate of phagocytosis and protease activity (Orozco et al, 1985;Ankri et al, 1998;1999), but other reports contradict this assumption (Spice and Ackers, 1992;Montfort et al, 1993).…”