# Defining how Entamoeba histolytica nibbles vs. devours human cells

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2020 · $219,171

## Abstract

Abstract
 Entamoeba histolytica is a protozoan pathogen and the causative agent of amoebiasis in humans. The
species name (histo-: tissue; lytic-: dissolving) derives from the ability to destroy host tissues. E. histolytica
trophozoites (“amoebae”) invade the large intestine, causing ulceration and can spread to other tissues (e.g.,
liver, lungs, brain), causing fatal abscesses. Amoebae possess contact-dependent cell-killing activity that is likely
to drive tissue damage, but the mechanism was unclear. We established a new paradigm by discovering that
amoebae kill by biting off and ingesting human cell fragments, which we named “amoebic trogocytosis” (trogo-:
nibble) (Ralston, et al., Nature, 2014). Building on this discovery, here we propose to delineate its
underlying mechanism. Trogocytosis is likely to share features with phagocytosis, since many proteins with
roles in phagocytosis are also required for trogocytosis. However, there are emerging hints that aspects of the
trogocytosis mechanism are distinct. Thus, we hypothesize that aspects of the trogocytosis mechanism are
distinct from phagocytosis. We will apply genetic and transcriptomic approaches to delineate the genes that
are shared between trogocytosis and phagocytosis, and those that are specific to each process. Beyond E.
histolytica, trogocytosis has far-reaching applications to eukaryotic biology. Several microbial eukaryotes appear
to use trogocytosis for cell-killing. In multicellular eukaryotes, trogocytosis is used for cell-killing, cell-cell
communication and cell-cell remodeling. Trogocytosis plays roles in the immune system, in the central nervous
system, and during development. Therefore, an improved understanding of the mechanism and biology of E.
histolytica trogocytosis will have a broad impact beyond amoebiasis. This work is significant and high-impact
as it will define the mechanism underlying trogocytosis and how it differs from phagocytosis. Our
approaches will also generate valuable new genetic tools. Moreover, our findings will apply directly to
amoebiasis pathogenesis, and broadly to other infections and the conserved process of trogocytosis.
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## Key facts

- **NIH application ID:** 10043675
- **Project number:** 1R21AI154163-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **Principal Investigator:** Katherine S Ralston
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $219,171
- **Award type:** 1
- **Project period:** 2020-06-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10043675

## Citation

> US National Institutes of Health, RePORTER application 10043675, Defining how Entamoeba histolytica nibbles vs. devours human cells (1R21AI154163-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10043675. Licensed CC0.

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