EhRho1 regulates phagocytosis by modulating actin dynamics through EhFormin1 and EhProfilin1 inEntamoeba histolytica

Abstract

The protist parasite Entamoeba histolytica causes amoebiasis, a major public health problem in developing countries and a major cause of morbidity and mortality. Invasive infection in amoebiasis mostly affects intestinal epithelial cell lining but can also involve other organs, such as liver, lungs, or brain. Phagocytosis is an essential mode of nutrition in amoeba and has often been associated with virulence behaviour of E. histolytica. E. histolytica possesses a highly dynamic and actin-rich cytoskeleton that is thought to be involved in many processes, such as motility, pseudopod formation, and pathogenesis. Rho GTPases are known to be key regulators of the actin cytoskeleton and consequently influence the shape and movement of cells. Our study is mainly focused to understand the role of EhRho1 in the phagocytosis process of E. histolytica. EhRho1 got enriched in the phagocytic cups along with EhActin and remains attached with phagosomal membrane. However, there was no direct binding of EhRho1 with G- or F-actin, though binding was observed with the actin nucleating proteins EhFormin1 and EhProfilin1. Overexpression of dominant negative mutant or lowering the expression by antisense RNA of EhRho1 in trophozoites caused delocalisation of EhFormin1 and EhProfilin1 from phagocytic cups, which results in impairment of phagocytic process and decrease in F-actin content. The overall results show that EhRho1 regulates phagocytosis by modulating actin dynamics through recruitment of EhFormin1 and EhProfilin1 at the phagocytosis nucleation site in E. histolytica.

Stress-induced nuclear depletion of Entamoeba histolytica 3′-5′ exoribonuclease EhRrp6 and its role in growth and erythrophagocytosis

“…Both the mRNA and protein levels were reduced. Because both proteins have been shown to modulate actin dynamics it is not surprising that reduction in their levels led to reduced phagocytosis (54,55). How EhRrp6 specifically targets selected genes is intriguing and needs to be further investigated.…”

Novel regulatory roles of PtdIns(4,5)P2generating enzyme EhPIPKI in actin dynamics and phagocytosis ofEntamoeba histolytica

“…Subsequently, EhC2PK, a C2‐domain‐containing protein kinase gets enriched at the site. EhC2PK recruits EhCaBP1 to the membrane and initiates phagocytic cup formation through further recruitment of other molecules such as EhAK1, EhARPC1, EhARPC2, and EhRho1 (Babuta, Kumar, Gourinath, Bhattacharya, & Bhattacharya, ; Babuta, Mansuri, Bhattacharya, & Bhattacharya, ; Bharadwaj, Sharma, Janhawi Arya, Bhattacharya, & Bhattacharya, ; Jain et al, ; Mansuri et al, ; Somlata, & S., & Bhattacharya, A., ). During the progression of phagocytic cups to phagosomes, other molecules, such as EhCaBP3, EhCaBP5, and myosin1B become part of the complex participating in pseudopod fusion and phagosome separation from the membrane (Aslam et al, ; Kumar et al, ).…”

EhC2B, a C2 domain-containing protein, promotes erythrophagocytosis in Entamoeba histolytica via actin nucleation

“…So far, we have observed that EhC2B localises at the phagocytic cup and pseudopods and is involved in erythrophagocytosis by the amoeba. However, the assembly of the actin monomer is essential for successful completion of the pseudopod formation as well as phagocytosis [10,38,39]. Several amoebic calcium-binding proteins are known to be involved in actin dynamics at the phagocytic cup [23,40].…”

“…Many actin regulatory/binding proteins govern the constant turnover of the actin filament [51]. In E. histolytica, several actin-binding proteins (ABPs) for example, EhFormin1, EhCaBP1, EhCaBP3, EhCoactosin, and EhNCABP116 have already been characterized and are shown to be involved in phagocytosis [10,12,23,27,52,53]. Ca 2+ is another prominent regulator of the actin cytoskeleton in E. histolytica [54,55].…”

“…Subsequently, this would require the participation of a large number of actin-associated proteins. These include actin nucleating, filament severing, endcapping bundling, membrane tethering, and scaffolding proteins [10][11][12][13][14][15]. Biochemically, pseudopods which are commonly used for the membrane protrusions while the cell is migrating on a substratum is reported to be distinct from the membrane extensions of the phagocytic cup, although morphologically they are similar [16].…”