An atypical venus fly trap domain receptor regulates motility and phagocytosis in the protozoan parasite Entamoeba histolytica

TL;DR

This study identifies a unique receptor in the parasite Entamoeba histolytica that helps it move and invade tissues, offering new insights into its disease mechanism.

Contribution

The discovery of an atypical GPI-anchored VFT receptor in E. histolytica that regulates motility and phagocytosis.

Findings

EhVFT is localized to the plasma membrane via a GPI anchor and mistargets to the mitosome when the GPI signal is removed.

Knockdown of EhVFT reduces parasite motility and phagocytosis by downregulating actin-related genes.

EhVFT shares structural features with signal-sensing proteins but lacks a transmembrane domain.

Abstract

Amebiasis is a parasitic infection of the human intestines, primarily caused by Entamoeba histolytica. Its pathogenesis relies on the environmental sensing-induced cytoskeletal remodeling as the basic mechanism for motility and tissue invasion. We identified and characterized an atypical Venus Fly-Trap (VFT) receptor protein, EhVFT (CL6EHI_096680). While it shares homology with the ligand-binding domain of class C GPCRs, it is phylogenetically related to the Periplasmic Binding Protein (PBP) superfamily. This protein is uniquely lacking a transmembrane domain. Instead, the glycosylphosphatidylinositol (GPI) anchor is responsible for its cell membrane localization. Removal of the GPI signal led to unexpected mitosomal localization, highlighting the importance of GPI modification in subcellular targeting. Functional studies revealed that EhVFT knockdown reduced parasite motility and phagocytosis of mammalian cells following the reduction of expression of actin cytoskeleton-related genes, including myosin II, villidin, and gelsolin. Our findings suggest that EhVFT plays a role in regulating downstream signaling linked to Entamoeba motility and phagocytosis. This study provides novel insights into an atypical VFT protein in E. histolytica, an area previously understudied.

Entamoeba histolytica is a human intestinal parasite that causes bloody diarrhea and often leads to fatal extraintestinal complications. This parasite can adhere to, consume, and invade intestinal cell layers in response to signals from its environment. In this study, we investigated a protein in the parasite E. histolytica, the Entamoeba histolytica Venus Fly Trap (EhVFT) domain receptor, which resembles a class C G-protein-coupled receptor in humans and Periplasmic Binding Protein (PBP) in bacteria known to sense signals and activate cellular responses. We found that EhVFT is located in the plasma membrane, facilitated by a lipid-associated anchoring mechanism known as the glycosylphosphatidylinositol (GPI) anchor. Removal of the predicted GPI-anchor signal caused the protein to be mistargeted to the mitosome, a degenerate and divergent mitochondrion-related organelle. It has also preserved the signal-sensing structure and the special structure commonly found in signal-sensing proteins. Knockdown of EhVFT expression significantly impaired the mobility and phagocytic activity of the parasite. Our findings suggest that EhVFT may be a crucial regulator of movement and invasion in E. histolytica, providing new insights into its biology and disease process.

Figures