Cellular internalization of cytolethal distending toxin : a new end to a known pathway

• The cytolethal distending toxins (CDTs) are unique in their ability to induce DNA damage, activate checkpoint responses and cause cell cycle arrest or apoptosis in intoxicated cells. However, little is known about their cellular internalization pathway. We demonstrate that binding of the Haemophilus ducreyi CDT (HdCDT) on the plasma membrane of sensitive cells was abolished by cholesterol extraction with methyl-beta-cyclodextrin. The toxin was internalized via the Golgi complex, and retrogradely transported to the endoplasmic reticulum (ER), as assessed by N-linked glycosylation. Further translocation from the ER did not require the ER-associated degradation (ERAD) pathway, and was Derlin-1 independent. The genotoxic activity of HdCDT was dependent on its internalization and its DNase activity, as induction of DNA double-stranded breaks was prevented in Brefeldin A-treated cells and in cells exposed to a catalytically inactive toxin. Our data contribute to a better understanding of the CDT mode of action and highlight two important aspects of the biology of this bacterial toxin family: (i) HdCDT translocation from the ER to the nucleus does not involve the classical pathways followed by other retrogradely transported toxins and (ii) toxin internalization is crucial for execution of its genotoxic activity.

Keyword

Animals

Bacterial Toxins/*metabolism/toxicity

Binding Sites

Brefeldin A/pharmacology

Cell Line

Cell Membrane/*metabolism

Cholesterol/metabolism

Cytosol/metabolism

DNA/metabolism

Deoxyribonucleases

Endoplasmic Reticulum/*metabolism

Golgi Apparatus/*metabolism

Haemophilus ducreyi/*metabolism

Hela Cells

Humans

Magnesium/metabolism

Mice

Mutation

Protein Transport

Research Support; Non-U.S. Gov't

MEDICINE

MEDICIN

Publication and Content Type

ref (subject category)

art (subject category)