The plasma membrane of Entamoeba histolytica: structure and dynamics*

Abstract

The plasma membrane components of the parasitic protozoan Entamoeba histolytica, the causative agent of human invasive amebiasis, have been biochemically and immunologically characterized during the last decade. In addition, genes coding for certain surface proteins have been cloned. In spite of these advances, a unified characterization of plasma membrane antigenic components of the parasite is still required for badly needed advancements in the design of useful diagnostic, epidemiologic, and immunoprophylactic tools. Here we review current knowledge on this issue and address the problem of the considerable variation in the electrophoretic profiles of plasma membrane proteins obtained by different groups. In addition, the differences in the degree of recognition of reported membrane antigens with human immune sera, and the diverse interpretations concerning the possible functions of the surface molecules characterized are discussed. A comparative analysis of plasma membrane proteins of E histolytica trophozoites using three different isolation methods revealed that it is possible to select for specific membrane proteins, depending on the lysis conditions. In our view, the method of Calderón and Avila preserves more proteins than other methods tested. Using sera from recent cases of invasive amebiasis studied by several laboratories in various geographical areas, a basic antigenic pattern of 11 principal proteins with molecular weights of 220, 170, 150, 125, 97, 80, 60, 45, 20 and 9 kDA was established for the pathogenic E histolytica strain HM1:IMSS, used by most research groups.

Differences in cap formation between invasive Entamoeba histolytica and non-invasive Entamoeba dispar

“…The remarkable ability of E. histolytica to rapidly regenerate substantial amounts of plasma membrane was demonstrated by the successive capping induced by repeated exposure to antibodies (Calderón et al 1990). Capping may be followed either by endocytosis and degradation of the incorporated membrane fragments, or by the gradual formation of a constriction ring and release of membranous cap vesicles (Espinosa-Cantellano and Martínez-Palomo 1991). At the end of the capping process, a spontaneous release of the cap may take place, the released caps containing most of the antibodies that originally bound to the whole cell surface.…”

31P‐NMR analysis of Entamoeba histolytica

“…The phosphoethanolamine unit of CDPEtn or the phosphocholine unit of CDPCho is then transferred to diacylglycerol to form phosphatidylethanolamine and phosphatidylcholine. Major phospholipids in amoebic whole extracts are phosphatidylcholine and two phosphatidylethanolamine species ; in addition, phosphatidic acid, phosphatidylinositol and phosphatidylserine have been identified (Aley et al, 1980;Cerbon and Flores, 1981 ;Espinosa-Cantellano and Martinez-Palomo, 1991). P,, PP,, NAD(P), nucleoside diphosphates and nucleoside triphosphates accounted for all the remaining signals in the 3'P-NMR spectrum.…”

Differences between the Large and Small Intestine in the Immunodominant Amoebic Proteins Recognized by IgG and IgA Antibodies in BALB/c Mice

“…In general, all the amoebic antigens recognized by mice samples have been described as immunodominant in humans at least by one group [35–41]. A basic pattern of 11 principal amoebic proteins with molecular weights of 220, 170, 150, 125, 80, 60, 45, 20 and 9 kDa is recognized by most sera from patients recovering from amoebic invasive episodes [38]. Most of these proteins were recognized by serum antibodies from i.p., i.m.…”

“…and rectally immunized mice although not all of them were strongly detected and thus could not be considered immunodominant. The immunodominant amoebic surface proteins 96, the 125 and 30 kDa proteins [38], were recognized by mice sera but not by samples from the small and large intestine. In this study, sera from GFT immunized mice recognized by IgM a band of 47 kDa and sera from i.m., and rectally immunized mice and samples from the small intestines recognized by IgG antibodies a band of 51 kDa.…”