English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Diphtheria toxin (DT) efficiently inhibits protein synthesis in human cells, resulting in severe disease diphtheria. The sensitivity towards DT varies between mammalian species. Mice and rats are resistant to DT. However, the reason underlying this insensitivity is controversially discussed and not well understood. Therefore, we investigated the steps of DT uptake, i.e. receptor binding and internalization into mouse J774A.1 macrophages and primary rat fibroblasts. We exploited the non-toxic DT-mutant cross-reacting material 197 (CRM197) and three additional receptor binding-deficient mutants (250 nM each) to investigate binding to cell surface and internalization into murine cells via flow cytometry and stimulated emission depletion (STED) super-resolution optical microscopy. Dual-color STED imaging unveiled CRM197 interacting with the murine precursor of the heparin-binding epidermal growth factor-like growth factor (HB-EGF). Moreover, we identified CRM197’s transmembrane domain as an additional HB-EGF binding site, which is also involved in the receptor-mediated internalization into murine cells. However, we do not find evidence for translocation of the catalytically active subunit (DTA) into the cytosol when 250 nM DT were applied. In conclusion, we provide evidence that the resistance of murine cells to DT is caused by an insufficiency of DTA to escape from endosomes and reach the cytosol. Possibly, a higher affinity interaction of DT and the HB-EGF is required for translocation, which highlights the role of the receptor in the endosomes during the translocation step. We extend the current knowledge about cellular uptake of the medically relevant DT and CRM197.   Electronic supplementary material  The online version of this article (10.1007/s00204-020-02731-4) contains supplementary material, which is available to authorized users.

archives of toxicology

Super-resolution microscopy unveils transmembrane domain-mediated internalization of cross-reacting material 197 into diphtheria toxin-resistant mouse J774A.1 cells and primary rat fibroblasts in vitro