Rab7D small GTPase is involved in phago‐, trogocytosis and cytoskeletal reorganization in the enteric protozoan Entamoeba histolytica

Abstract

Rab small GTPases regulate membrane traffic between distinct cellular compartments of all eukaryotes in a tempo-spatially specific fashion. Rab small GTPases are also involved in the regulation of cytoskeleton and signalling. Membrane traffic and cytoskeletal regulation play pivotal role in the pathogenesis of Entamoeba histolytica, which is a protozoan parasite responsible for human amebiasis. E. histolytica is unique in that its genome encodes over 100 Rab proteins, containing multiple isotypes of conserved members (e.g., Rab7) and Entamoeba-specific subgroups (e.g., RabA, B, and X). Among them, E. histolytica Rab7 is the most diversified group consisting of nine isotypes. While it was previously demonstrated that EhRab7A and EhRab7B are involved in lysosome and phagosome biogenesis, the individual roles of other Rab7 members and their coordination remain elusive. In this study, we characterised the third member of Rab7, Rab7D, to better understand the significance of the multiplicity of Rab7 isotypes in E. histolytica. Overexpression of EhRab7D caused reduction in phagocytosis of erythrocytes, trogocytosis (meaning nibbling or chewing of a portion) of live mammalian cells, and phagosome acidification and maturation. Conversely, transcriptional gene silencing of EhRab7D gene caused opposite phenotypes in phago/trogocytosis and phagosome maturation. Furthermore, EhRab7D gene silencing caused reduction in the attachment to and the motility on the collagen-coated surface. Image analysis showed that EhRab7D was occasionally associated with lysosomes and prephagosomal vacuoles, but not with mature phagosomes and trogosomes. Finally, in silico prediction of structural organisation of EhRab7 isotypes † These authors contributed equally to this study.

Trogocytosis in Unicellular Eukaryotes

“…Among unicellular eukaryotes, trogocytosis have been best studied in E. histolytica at the molecular level [ 16 , 29 , 34 , 105 , 106 ]. Proteins and lipids involved in trogocytosis are largely conserved between human and E. histolytica .…”

Shaping of T Cell Functions by Trogocytosis

“…Specifically, several studies have utilized the ability of CD8 + T cells to acquire antigen peptide-MHCI complexes in order to detect antigen-specific T cells in peripheral blood mononuclear cells (PBMCs) from patients infected with human T-cell lymphotropic virus type I (HTLV-1) or lymphocytic choriomeningitis virus (LCMV). Tomaru et al first successfully identified T cell populations that specifically recognize the HTLV-I Tax (11)(12)(13)(14)(15)(16)(17)(18)(19) peptide presented on HLA-A*201 [131]. In this study, the authors established Hmy2.CIR cells, an HLA-A and HLA-B locus-defective immortalized B cell line, transduced with HLA-A*201 fused with GFP.…”

“…Trogocytosis has been observed not only in immune cell interactions, but also during epithelial cell communication [9] and in neuronal synapses [10,11]. Further, trogocytosis is used by amoebae to kill host cells [12,13], indicating that this biological phenomenon is widely conserved throughout eukaryotes.…”

“…Trogocytosis has been observed not only in immune cell interactions, but also during epithelial cell communication [ 9 ] and in neuronal synapses [ 10 , 11 ]. Further, trogocytosis is used by amoebae to kill host cells [ 12 , 13 ], indicating that this biological phenomenon is widely conserved throughout eukaryotes. Recent findings of trogocytosis in microbes [ 14 ], mammalian neuronal networks [ 15 , 16 ], and non-T cell immune cell interactions [ 2 , 17 , 18 ] have been well summarized by others previously and also in this issue.…”

Signals and signal transduction pathways in Entamoeba histolytica during the life cycle and when interacting with bacteria or human cells

“…Small GTPases from the Rab family are also important factors leading to phagosome maturation and vesicular traffic (Verma et al, 2020); for example, RabA, RabB, Rab5, Rab7A, Rab8A, and Rab35 are involved in the formation of the phagocytic cup and in phagolysosomal biogenesis (Verma & Datta, 2017). In addition, EhRab7D has a inhibitory role in phagocytosis and trogocytosis (Saito‐Nakano et al, 2020).…”