Ricin Cytotoxicity Is Sensitive to Recycling between the Endoplasmic Reticulum and the Golgi Complex

doi:10.1074/jbc.270.34.20078

Ricin Cytotoxicity Is Sensitive to Recycling between the Endoplasmic Reticulum and the Golgi Complex (*)

From the (1)Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom and the
(2) Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037

Abstract

Cytotoxic proteins that kill mammalian cells by catalytically inhibiting protein synthesis must enter the cytosol in order to reach their substrates. With the exception of diphtheria toxin, which enters the cytosol from acidified endosomes, the intracellular site of translocation of other toxins including ricin, Escherichia coli Shiga-like toxin-1, and Pseudomonas exotoxin A is likely to involve early compartments of the secretory pathway. We have used a molecular approach to identify the site and mechanism of toxin delivery to the cytosol by transiently expressing mutant GTPases that inhibit the assembly of biochemical complexes mediating anterograde and retrograde transport in the exocytic and endocytic pathways. The results provide evidence to suggest that receptors actively recycling between the endoplasmic reticulum and terminal Golgi compartments are essential for toxin translocation to the cytosol from the endoplasmic reticulum. The rapid kinetics of intoxication demonstrate a substantial level of bidirectional membrane flow and sorting through the early secretory pathway.

Footnotes

↵^§ Both authors contributed equally to this study.
↵* This work was supported by National Institutes of Health Grant GM42336 (to W. E. B.) and Grant 88/T02035 from the United Kingdom Biotechnology and Biological Sciences Research Council (to J. M. L. and L. M. R.). This is The Scripps Research Institute Manuscript 9193-CB. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

TGN

trans-Golgi network

ER

endoplasmic reticulum

SLT-1

Shiga-like toxin-1

PBS

phosphate-buffered saline

VSV

vesicular stomatitis virus

DMEM

Dulbecco's modified Eagle's medium.
↵²M. Aridor, T. Rowe, S. Bannykh, and W. E. Balch, submitted for publication.
↵³D. Fitzgerald, personal communication.
- Received May 12, 1995.