Comparative proteomic analysis of two Entamoeba histolytica strains with different virulence phenotypes identifies peroxiredoxin as an important component of amoebic virulence

Abstract

SummaryEntamoeba histolytica is a protozoan intestinal parasite that causes amoebic colitis and amoebic liver abscess. To identify virulence factors of E. histolytica, we first defined the phenotypes of two E. histolytica strains, HM-1:IMSS, the prototype virulent strain, and E. histolytica Rahman, a strain that was reportedly less virulent than HM-1:IMSS. We found that compared with HM-1:IMSS, Rahman has a defect in erythrophagocytosis and the ability to cause amoebic colitis in human colonic xenografts. We used differential in-gel 2D electrophoresis to compare the proteome of Rahman and HM-1:IMSS, and identified six proteins that were differentially expressed above a fivefold level between the two organisms. These included two proteins with antioxidative properties (peroxiredoxin and superoxide dismutase), and three proteins of unknown function, grainin 1, grainin 2 and a protein containing a LIM-domain. Overexpression of peroxiredoxin in Rahman rendered the transgenic trophozoites more resistant to killing by H 2O2 in vitro, and infection with Rahman trophozoites expressing higher levels of peroxiredoxin was associated with higher levels of intestinal inflammation in human colonic xenografts, and more severe disease based on histology. In contrast, higher levels of grainin appear to be associated with a reduced virulence phenotype, and E. histolytica HM-1:IMSS trophozoites infecting human intestinal xenografts show marked decreases in grainin expression. Our data indicate that there are definable molecular differences between Rahman and HM-1:IMSS that may explain the phenotypic differences, and identify peroxiredoxin as an important component of virulence in amoebic colitis.

EhLimA, a Novel LIM Protein, Localizes to the Plasma Membrane inEntamoeba histolytica

“…Since first described nearly 2 decades ago (21,28,57), LIM domain-containing proteins have been identified in a wide range of eukaryotes, including protozoa (16,30,45), plants (5,20,40), and yeast (Saccharomyces cerevisiae) (39), stressing the evolutionary importance of these proteins. In the parasitic protozoan Entamoeba histolytica, a few studies have revealed the presence of such proteins (17,36), although to date, no LIM domain-containing proteins have been characterized in this organism. The name LIM is derived from the three developmentally regulated transcription factors, LIN-11 of Caenorhabditis elegans (21), Isl1 of rat (28), and MEC-3 of C. elegans (57) in which the LIM domain was initially identified.…”

Identification of an Entamoeba histolytica Serine-, Threonine-, and Isoleucine-Rich Protein with Roles in Adhesion and Cytotoxicity

“…The authors hypothesized that the glycans may protect parasite adhesion molecules from proteolysis or that the proteophosphoglycans may regulate the ability of parasite surface molecules to interact with host cell receptors. Two genes with lower expression in E. histolytica Rahman have been genetically linked to virulence: overexpression of the peroxiredoxin gene in E. histolytica Rahman imparted increased resistance to oxidative stress (19), and antisense inhibition of the light lectin subunit in E. histolytica HM-1:IMSS resulted in decreased cytotoxicity and fewer amebic liver abscesses in hamsters (3).…”

“…This strain, originally isolated from an asymptomatically infected person (21, 34) has long been described as having attenuated virulence (14). E. histolytica Rahman was recently shown to have decreased levels of cytotoxicity, decreased ability to phagocytose erythrocytes, decreased ability to elicit colitis in human colonic xenografts, and decreased resistance to oxidative stress (19). Interestingly, relatively few genetic differences were noted between E. histolytica HM-1:IMSS and E. histolytica Rahman based on comparative genomic hybridization analysis (45).…”

“…Some genes involved in amebic pathogenesis are expressed at lower levels in E. histolytica Rahman, including cysteine proteases (EhCP6, EhCP4, EhCP7), gene products important in bacterial killing (AIG1, lysozyme) and stress response (70-kDa heat shock protein, peroxiredoxin) (18,19), and the light subunit of the Gal/GalNAc lectin (3). Additionally, the proteophosphoglycans coating the surface of E. histolytica Rahman have truncated glucan side chains compared to those of the virulent E. histolytica HM-1:IMSS (35).…”

Knockdown of Five Genes Encoding Uncharacterized Proteins Inhibits Entamoeba histolytica Phagocytosis of Dead Host Cells

“…In areas where the infection is highly endemic, such as the Mirpur region of Dhaka, Bangladesh, over 50% of children may become infected by 5 years of age (3), yet only about 10% of all infections become symptomatic (4,5). Isolated strains of E. histolytica have been shown to have different levels of virulence both in vivo and in vitro (6)(7)(8), which may in part determine whether or not a particular infection becomes invasive.…”