EhCoactosin Stabilizes Actin Filaments in the Protist Parasite Entamoeba histolytica

Abstract

Entamoeba histolytica is a protist parasite that is the causative agent of amoebiasis, and is a highly motile organism. The motility is essential for its survival and pathogenesis, and a dynamic actin cytoskeleton is required for this process. EhCoactosin, an actin-binding protein of the ADF/cofilin family, participates in actin dynamics, and here we report our studies of this protein using both structural and functional approaches. The X-ray crystal structure of EhCoactosin resembles that of human coactosin-like protein, with major differences in the distribution of surface charges and the orientation of terminal regions. According to in vitro binding assays, full-length EhCoactosin binds both F- and G-actin. Instead of acting to depolymerize or severe F-actin, EhCoactosin directly stabilizes the polymer. When EhCoactosin was visualized in E. histolytica cells using either confocal imaging or total internal reflectance microscopy, it was found to colocalize with F-actin at phagocytic cups. Over-expression of this protein stabilized F-actin and inhibited the phagocytic process. EhCoactosin appears to be an unusual type of coactosin involved in E. histolytica actin dynamics.

Formation of oxidised (OX) proteins inEntamoeba histolyticaexposed to auranofin and consequences on the parasite virulence

“…A common group of enriched OXs that are represented in AF‐, MTZ‐ and H 2 O 2 ‐treated trophozoites is the cytoskeletal proteins. E. histolytica 's virulence depends on an intact cytoskeleton (Gautam, Ali, Bhattacharya, & Gourinath, ; Kumar, Dutta, Maiti, & Gourinath, ; Manich et al, ), and our previous work has shown that oxidation of its cytoskeletal proteins has a direct effect on the mobility of the parasite and on its virulence (Shahi, Trebicz‐Geffen, Nagaraja, Alterzon‐Baumel, et al, ). It has also been demonstrated that MTZ has a direct effect on E. histolytica motility (Nesthus, Glette, Bjorvatn, & Solberg, ).…”

The actin cytoskeleton orchestra in Entamoeba histolytica

“…We have compiled a total of 11 different proteins, of which only one protein has been annotated as actophorin (C4LVG4). An earlier work published by Kumar et al described a unique coactosin (C4M4P4) that stabilized actin filaments rather than performing its regular severing action 19,73 . This role‐reversal in the mechanism of action of coactosin sheds light on the yet undiscovered roles of ADF/cofilin family proteins.…”

“…The subtle difference observed here might have led to differences in the ABPs as well. One of such documentations was seen in EhCoactosin, an actin depolymerizing factor (ADF) family protein that stabilized actin filaments, instead of severing/depolymerizing them 19 . Very few ABPs are identified from Entamoeba histolytica , and a handful are experimentally validated 20 .…”

Calcium-binding protein EhCaBP3 is recruited to the phagocytic complex ofEntamoeba histolyticaby interacting with Arp2/3 complex subunit 2

“…The initiation of signalling pathway after attachment of a particle (such as red blood cell [RBC]) takes place with enrichment of EhC2PK in the presence of Ca 2+ at the site of attachment (Somlata & Bhattacharya, 2011). EhAK1 and Arp2/3 complex proteins are then sequentially recruited, and this basic complex, with the help of a number of actin binding and other proteins, is responsible for the formation and progression of the phagocytic cup towards its closure (Babuta, Mansuri, Bhattacharya, & Bhattacharya, 2015;N. EhAK1 and Arp2/3 complex proteins are then sequentially recruited, and this basic complex, with the help of a number of actin binding and other proteins, is responsible for the formation and progression of the phagocytic cup towards its closure (Babuta, Mansuri, Bhattacharya, & Bhattacharya, 2015;N.…”

“…EhC2PK then recruits EhCaBP1 in a process that is independent of Ca 2+ . EhAK1 and Arp2/3 complex proteins are then sequentially recruited, and this basic complex, with the help of a number of actin binding and other proteins, is responsible for the formation and progression of the phagocytic cup towards its closure (Babuta, Mansuri, Bhattacharya, & Bhattacharya, 2015;N. Kumar, Somlata, Dutta, Maiti, & Gourinath, 2014;Mansuri et al, 2016;Mansuri, Bhattacharya, & Bhattacharya, 2014;Voigt, Olivo, Sansonetti, & Guillen, 1999).…”