Geldanamycin Enhances Retrograde Transport of Shiga Toxin in HEp-2 Cells.

Anne Berit Dyve Lingelem,Kirsten Sandvig,Maria Lyngaas Torgersen,Roger Simm,Ieva Ailte Hjelseth,Matthew Seaman

doi:10.1371/journal.pone.0129214

Anne Berit Dyve Lingelem, Kirsten Sandvig + Show 4 more

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https://doi.org/10.1371/journal.pone.0129214

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Journal: PloS one	Publication Date: May 27, 2015
Citations: 3	License type: CC BY 4.0

Affiliation: Oslo University Hospital, University of Oslo

Abstract

The heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) has been shown to alter endosomal sorting, diverting cargo destined for the recycling pathway into the lysosomal pathway. Here we investigated whether GA also affects the sorting of cargo into the retrograde pathway from endosomes to the Golgi apparatus. As a model cargo we used the bacterial toxin Shiga toxin, which exploits the retrograde pathway as an entry route to the cytosol. Indeed, GA treatment of HEp-2 cells strongly increased the Shiga toxin transport to the Golgi apparatus. The enhanced Golgi transport was not due to increased endocytic uptake of the toxin or perturbed recycling, suggesting that GA selectively enhances endosomal sorting into the retrograde pathway. Moreover, GA activated p38 and both inhibitors of p38 or its substrate MK2 partially counteracted the GA-induced increase in Shiga toxin transport. Thus, our data suggest that GA-induced p38 and MK2 activation participate in the increased Shiga toxin transport to the Golgi apparatus.

Highlights

The benzoquinoid ansamycin antibiotic geldanamycin (GA) produced by Streptomyces hygroscopicus is a potent inhibitor of heat shock protein 90 (Hsp90) proteins, and has been extensively studied due to its anti-tumor activity [1,2]
To corroborate that the GA-induced increase in Shiga toxin transport is mediated by Hsp90 inhibition, we tested the structurally different Hsp90 inhibitor radicicol, which binds to the ATP-binding pocket of Hsp90
In this study we have investigated the effect of the Hsp90 inhibitor GA on retrograde transport to the Golgi apparatus

Summary

Introduction

The benzoquinoid ansamycin antibiotic geldanamycin (GA) produced by Streptomyces hygroscopicus is a potent inhibitor of Hsp proteins, and has been extensively studied due to its anti-tumor activity [1,2]. Hsp proteins are ubiquitously and abundantly expressed molecular chaperones whose main function is to stabilize proteins and assist in protein folding. The cytosolic Hsp has been best characterized, but other compartment-specific Hsp proteins exist [2,3,4]. More than 200 client proteins of Hsp have so far been identified, many of which are oncoproteins [3,4]. GA binds to the ATP binding pocket of Hsp, thereby interrupting its chaperone cycle, leading to degradation of many of the client proteins [1,2]

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