# Hypofucosylation promotes pertussis toxin binding to cell surface glycococonjugates and pertussis toxin-induced intracellular ERK signaling

## TL;DR

This study shows that reduced fucose on cell surfaces increases pertussis toxin binding and signaling, worsening immune impacts of whooping cough.

## Contribution

The study reveals that fucosylation protects cells from pertussis toxin by reducing its binding and downstream ERK signaling.

## Key findings

- Fucosylation inhibits pertussis toxin binding to cell surface glycans.
- Reduced fucose leads to increased ERK signaling in T cells via pertussis toxin.
- FUT3/FUT5/FUT6 and FUT8 knockout cells show enhanced pertussis toxin binding.

## Abstract

Pertussis (whooping cough) is caused by the bacterium Bordetella pertussis. Among the virulence factors produced by B. pertussis, pertussis toxin (PT) is responsible for key disease symptoms, including impacts on the immune system. PT is an AB5 toxin, consisting of a single catalytic A subunit and five B subunits. The B pentamer recognizes cell surface glycans and facilitates intracellular delivery of the catalytic A subunit. PT also impacts host cell signaling via mechanisms that do not depend on the catalytic activity of the A subunit. In particular, PT promotes signaling through the T-cell receptor (TCR), leading to activation of extracellular signal-regulated kinase (ERK) cascades. PT prefers to bind sialylated and N-linked glycans, but other aspects of PT’s glycan binding specificity remain underexplored. Here we report that the absence of fucose on mammalian cell surfaces leads to increased binding by PT. Using pharmacological inhibitors in a human bronchial epithelial cell line, we observe that sialylation and N-linked glycosylation promote PT binding while fucosylation interferes with PT binding. Similarly, CHO and Colo205 cells deficient in fucosylation exhibited enhanced PT binding as compared to the corresponding wild-type cell lines. Genetic knockout of FUT3/FUT5/FUT6 or of FUT8 led to increased PT binding, suggesting that specific fucosylated epitopes mediate protection from PT. The functional impact of altered PT binding was examined in Jurkat T cells, where removal of cell surface non-core fucose led to increased PT-dependent ERK phosphorylation. In sum, our study identifies a role for fucosylation in protecting mammalian cells from PT.