Letter | Published:

Trogocytosis by Entamoeba histolytica contributes to cell killing and tissue invasion

Nature volume 508, pages 526530 (24 April 2014) | Download Citation

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Abstract

Entamoeba histolytica is the causative agent of amoebiasis, a potentially fatal diarrhoeal disease in the developing world. The parasite was named “histolytica” for its ability to destroy host tissues, which is probably driven by direct killing of human cells. The mechanism of human cell killing has been unclear, although the accepted model was that the parasites use secreted toxic effectors to kill cells before ingestion1. Here we report the discovery that amoebae kill by ingesting distinct pieces of living human cells, resulting in intracellular calcium elevation and eventual cell death. After cell killing, amoebae detach and cease ingestion. Ingestion of human cell fragments is required for cell killing, and also contributes to invasion of intestinal tissue. The internalization of fragments of living human cells is reminiscent of trogocytosis (from Greek trogo, nibble) observed between immune cells2,3,4,5,6, but amoebic trogocytosis differs because it results in death. The ingestion of live cell material and the rejection of corpses illuminate a stark contrast to the established model of dead cell clearance in multicellular organisms7. These findings change the model for tissue destruction in amoebiasis and suggest an ancient origin of trogocytosis as a form of intercellular exchange.

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Acknowledgements

We thank J. A. Redick and S. J. Guillot for assistance with sample preparation for electron microscopy and D. A. Zemo of Olympus for assistance with multiphoton microscopy. We thank the University of Virginia Research Histology Core for assistance with preparation of frozen sections. We thank J. E. Casanova, J. D. Castle, J. Lannigan, K. S. Ravichandran and R. P. Taylor for helpful discussions. The artwork (Extended Data Fig. 1) was prepared by A. Impagliazzo. K.S.R. was supported by a Howard Hughes Medical Institute Postdoctoral Fellowship from the Life Sciences Research Foundation, and a Postdoctoral Fellowship from the Hartwell Foundation. N.M.M.-L. was supported by NIH Training Grant AI07046-32. This work was supported by NIH grant 5R01 AI-26649 to W.A.P.

Author information

Affiliations

  1. Department of Medicine, University of Virginia, Charlottesville, Virginia 22908, USA

    • Katherine S. Ralston
    • , Nicole M. Mackey-Lawrence
    •  & William A. Petri Jr
  2. Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, Virginia 22908, USA

    • Michael D. Solga
    •  & William A. Petri Jr
  3. School of Life Sciences, Jawaharlal Nehru University, 110067 New Delhi, India

    • Somlata
    •  & Alok Bhattacharya
  4. Department of Pathology, University of Virginia, Charlottesville, Virginia 22908, USA

    • William A. Petri Jr

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Contributions

K.S.R. designed, performed and analysed the experiments. W.A.P. oversaw experimental design and analysis. M.D.S. assisted with Amnis Imagestream experimental design and with collection and analysis of Amnis Imagestream data. N.M.M.-L. assisted with isolation and preparation of mouse tissue for ex vivo imaging. S. and A.B. contributed plasmids and antibodies for the study of EhC2PK and contributed to analysis. K.S.R. and W.A.P. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to William A. Petri Jr.

Extended data

Supplementary information

Videos

  1. 1.

    Live confocal microscopy time lapse demonstrating that bites of human cell material are internalized by the amoebae

    Ingestion of bites occurs while human Jurkat cells are viable and ceases once they are dead. Human cells were pre-labeled with DiI (red; cell membrane), Flou4 (green; intracellular Ca2+); and SYTOX blue (blue; nucleic acid in permeable cells) was present in the media during imaging. Images were collected every 30 seconds are played back at 1 frame per second.

  2. 2.

    Live confocal microscopy time lapse demonstrating that human cell intracellular calcium elevation follows the ingestion of bites

    Human Jurkat cells were pre-labeled with DiD (pink; cell membrane), and Flou4 (green; intracellular Ca2+). Images were collected every 20 seconds and are played back at 1 frame per second.

  3. 3.

    3-D reconstruction of live 4-D confocal microscopy demonstrating that amoebic trogocytosis occurs with human red blood cells and that they are not fully internalized by the amoebae

    Human red blood cells were pre-labeled with DiD (pink; cell membrane) and amoebae were pre-labeled with CMFDA (green). Z-stacks were collected continuously. The Video is played back at 1 frame per second.

  4. 4.

    Surface rendered version of Video 3 demonstrating that amoebic trogocytosis occurs with human red blood cells and that they are not fully internalized

    Red blood cells are shown in pink and the amoeba in green.

  5. 5.

    Live 4-D multiphoton microscopy with amoebae interacting with ex vivo mouse intestinal tissue, demonstrating that amoebic trogocytosis occurs during amoebic tissue invasion

    Intestinal tissue was from the cecum of a mouse expressing membrane-targeted enhanced green fluorescent protein (EGFP) and amoebae were pre-labeled with calcein violet (blue; intracellular esterase activity). Shown is one X-Y plane from the 3-D reconstruction of the 4-D data. Z-stacks were collected continuously. The Video is played back at 1 frame per second.

  6. 6.

    3-D reconstruction of the live 4-D multiphoton microscopy dataset from Video 5

    Shown is a subset of the total collected Z-height, as a 3-D reconstruction with membrane targeted EGFP shown false-colored in yellow and amoebae in blue.

  7. 7.

    Live 4-D multiphoton microscopy with amoebae interacting with ex vivo mouse intestinal tissue, demonstrating that amoebic trogocytosis occurs during amoebic tissue invasion

    Shown is one X-Y plane from the 3-D reconstruction of the 4-D data. Note that ingestion of bites of mouse cells occurs prior to amoebic tissue invasion in the Z-axis (visualized as loss of the amoeba from the X-Y plane). Intestinal tissue was from the cecum of a mouse expressing membrane-targeted EGFP (yellow false color) and amoebae were pre-labeled with calcein violet (blue; intracellular esterase activity). Z-stacks were collected continuously. The Video is played back at 1 frame per second.

  8. 8.

    3-D reconstruction of the live 4-D multiphoton microscopy dataset from Video 7

    Shown is a subset of the total collected Z-height, as a 3-D reconstruction with membrane targeted EGFP shown false-colored in yellow and amoebae in blue. An amoeba can be seen invading the tissue in the Z-axis.

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DOI

https://doi.org/10.1038/nature13242

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