Induction of Direct Endosome to Endoplasmic Reticulum Transport in Chinese Hamster Ovary (CHO) Cells (LdlF) with a Temperature-sensitive Defect in ϵ-Coatomer Protein (ϵ-COP)
In the present study we demonstrate that ricin, apparently without passing through the Golgi apparatus, reaches the endoplasmic reticulum (ER) and intoxicates cells in which the Golgi apparatus has been vesiculated by depletion of ϵ-COP, a subunit of COPI. LdlF cells contain a temperature-sensitive...
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Published in | The Journal of biological chemistry Vol. 278; no. 37; p. 35850 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
American Society for Biochemistry and Molecular Biology
12.09.2003
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Online Access | Get full text |
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Summary: | In the present study we demonstrate that ricin, apparently without passing
through the Golgi apparatus, reaches the endoplasmic reticulum (ER) and
intoxicates cells in which the Golgi apparatus has been vesiculated by
depletion of ϵ-COP, a subunit of COPI. LdlF cells contain a
temperature-sensitive mutation in ϵ-COP. At the nonpermissive temperature
ϵ-COP is degraded, and the Golgi apparatus undergoes a morphological
change. To study ricin transport in these cells we used ricin sulf-2, a
modified ricin molecule containing glycosylation and sulfation sites.
Measurements of the incorporation of radioactive mannose into ricin sulf-2
showed that ricin reached the ER in cells depleted of ϵ-COP. Importantly,
by investigating the glycosylation of ricin sulf-2 that was modified with
radioactive sulfate in the trans-Golgi network, it was demonstrated that
transport of ricin to the ER via the Golgi apparatus was severely inhibited.
Moreover, we found that ricin was able to intoxicate ldlF cells depleted of
ϵ-COP in the presence of brefeldin A. In contrast, control cells were
completely protected against ricin by brefeldin A. In conclusion, our results
suggest that in ldlF cells depleted of ϵ-COP ricin might be transported
to the ER by an induced brefeldin A-resistant pathway that circumvents the
Golgi apparatus. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M303425200 |