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Saporin and ricin A chain follow different intracellular routes to enter the cytosol of intoxicated cells

Saporin and ricin A chain follow different intracellular routes to enter the cytosol of intoxicated cells
Saporin and ricin A chain follow different intracellular routes to enter the cytosol of intoxicated cells
Several protein toxins, such as the potent plant toxin ricin, enter mammalian cells by endocytosis and undergo retrograde transport via the Golgi complex to reach the endoplasmic reticulum (ER). In this compartment the catalytic moieties exploit the ER-associated degradation (ERAD) pathway to reach their cytosolic targets. Bacterial toxins such as cholera toxin or Pseudomonas exotoxin A carry KDEL or KDEL-like C-terminal tetrapeptides for efficient delivery to the ER. Chimeric toxins containing monomeric plant ribosome-inactivating proteins linked to various targeting moieties are highly cytotoxic, but it remains unclear how these molecules travel within the target cell to reach cytosolic ribosomes. We investigated the intracellular pathways of saporin, a monomeric plant ribosome-inactivating protein that can enter cells by receptor-mediated endocytosis. Saporin toxicity was not affected by treatment with Brefeldin A or chloroquine, indicating that this toxin follows a Golgi-independent pathway to the cytosol and does not require a low pH for membrane translocation. In intoxicated Vero or HeLa cells, ricin but not saporin could be clearly visualized in the Golgi complex using immunofluorescence. The saporin signal was not evident in the Golgi, but was found to partially overlap with that of a late endosome/lysosome marker. Consistently, the toxicities of saporin or saporin-based targeted chimeric polypeptides were not enhanced by the addition of ER retrieval sequences. Thus, the intracellular movement of saporin differs from that followed by ricin and other protein toxins that rely on Golgi-mediated retrograde transport to reach their retrotranslocation site.
anticancer therapy, bacterial toxins, intracellular trafficking, KDEL retrieval sequence, plant ribosome-inactivating proteins
1742-464X
4983-4995
Vago, Richard
d9ed3009-1084-4e22-9c3b-ab0fdb1eee59
Marsden, Catherine J.
dfc1bc5f-6ffb-405d-b351-95bb582a826c
Lord, J. Michael
a5c49f85-ae38-4336-a897-868ffb3f2da4
Ippoliti, Rodolfo
b7a45d58-6d17-47a8-ad93-fc1acf618c35
Flavell, David J.
3a0f7124-7d44-42bc-b6f6-6fb12552fbd6
Flavell, Sopsamorn U.
fa2b4670-1836-42e2-b68a-5d646899d711
Ceriotti, Aldo
ae63c14a-43f9-4f3e-96a4-77c639b7229b
Fabbrini, M. Serena
5f37057e-6f68-4513-9056-7475d6b34902
Vago, Richard
d9ed3009-1084-4e22-9c3b-ab0fdb1eee59
Marsden, Catherine J.
dfc1bc5f-6ffb-405d-b351-95bb582a826c
Lord, J. Michael
a5c49f85-ae38-4336-a897-868ffb3f2da4
Ippoliti, Rodolfo
b7a45d58-6d17-47a8-ad93-fc1acf618c35
Flavell, David J.
3a0f7124-7d44-42bc-b6f6-6fb12552fbd6
Flavell, Sopsamorn U.
fa2b4670-1836-42e2-b68a-5d646899d711
Ceriotti, Aldo
ae63c14a-43f9-4f3e-96a4-77c639b7229b
Fabbrini, M. Serena
5f37057e-6f68-4513-9056-7475d6b34902

Vago, Richard, Marsden, Catherine J., Lord, J. Michael, Ippoliti, Rodolfo, Flavell, David J., Flavell, Sopsamorn U., Ceriotti, Aldo and Fabbrini, M. Serena (2005) Saporin and ricin A chain follow different intracellular routes to enter the cytosol of intoxicated cells. Febs Journal, 272 (19), 4983-4995. (doi:10.1111/j.1742-4658.2005.04908.x).

Record type: Article

Abstract

Several protein toxins, such as the potent plant toxin ricin, enter mammalian cells by endocytosis and undergo retrograde transport via the Golgi complex to reach the endoplasmic reticulum (ER). In this compartment the catalytic moieties exploit the ER-associated degradation (ERAD) pathway to reach their cytosolic targets. Bacterial toxins such as cholera toxin or Pseudomonas exotoxin A carry KDEL or KDEL-like C-terminal tetrapeptides for efficient delivery to the ER. Chimeric toxins containing monomeric plant ribosome-inactivating proteins linked to various targeting moieties are highly cytotoxic, but it remains unclear how these molecules travel within the target cell to reach cytosolic ribosomes. We investigated the intracellular pathways of saporin, a monomeric plant ribosome-inactivating protein that can enter cells by receptor-mediated endocytosis. Saporin toxicity was not affected by treatment with Brefeldin A or chloroquine, indicating that this toxin follows a Golgi-independent pathway to the cytosol and does not require a low pH for membrane translocation. In intoxicated Vero or HeLa cells, ricin but not saporin could be clearly visualized in the Golgi complex using immunofluorescence. The saporin signal was not evident in the Golgi, but was found to partially overlap with that of a late endosome/lysosome marker. Consistently, the toxicities of saporin or saporin-based targeted chimeric polypeptides were not enhanced by the addition of ER retrieval sequences. Thus, the intracellular movement of saporin differs from that followed by ricin and other protein toxins that rely on Golgi-mediated retrograde transport to reach their retrotranslocation site.

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More information

Published date: 2005
Keywords: anticancer therapy, bacterial toxins, intracellular trafficking, KDEL retrieval sequence, plant ribosome-inactivating proteins

Identifiers

Local EPrints ID: 26650
URI: http://eprints.soton.ac.uk/id/eprint/26650
ISSN: 1742-464X
PURE UUID: ead7300d-a326-47b4-8351-1f168c5452df

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Date deposited: 10 Apr 2006
Last modified: 15 Mar 2024 07:12

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Contributors

Author: Richard Vago
Author: Catherine J. Marsden
Author: J. Michael Lord
Author: Rodolfo Ippoliti
Author: David J. Flavell
Author: Sopsamorn U. Flavell
Author: Aldo Ceriotti
Author: M. Serena Fabbrini

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