Repair of a Bacterial Small β-Barrel Toxin Pore Depends on Channel Width.

Martina Meyenburg,Amable J. Rivas,Sapun Parekh,Matthias Husmann,Cesare Montecucco,Arturo Zychlinsky,Gisela von Hoven,Nadja Hellmann,Qianqian Qin,Claudia Neukirch

doi:10.1128/mbio.02083-16

Martina Meyenburg, Amable J. Rivas + Show 8 more

Open Access

https://doi.org/10.1128/mbio.02083-16

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Abstract

ABSTRACTMembrane repair emerges as an innate defense protecting target cells against bacterial pore-forming toxins. Here, we report the first paradigm of Ca2+-dependent repair following attack by a small β-pore-forming toxin, namely, plasmid-encoded phobalysin of Photobacterium damselae subsp. damselae. In striking contrast, Vibrio cholerae cytolysin, the closest ortholog of phobalysin, subverted repair. Mutational analysis uncovered a role of channel width in toxicity and repair. Thus, the replacement of serine at phobalysin´s presumed channel narrow point with the bulkier tryptophan, the corresponding residue in Vibrio cholerae cytolysin (W318), modulated Ca2+ influx, lysosomal exocytosis, and membrane repair. And yet, replacing tryptophan (W318) with serine in Vibrio cholerae cytolysin enhanced toxicity. The data reveal divergent strategies evolved by two related small β-pore-forming toxins to manipulate target cells: phobalysin leads to fulminant perturbation of ion concentrations, closely followed by Ca2+ influx-dependent membrane repair. In contrast, V. cholerae cytolysin causes insidious perturbations and escapes control by the cellular wounded membrane repair-like response.

Highlights

Membrane repair emerges as an innate defense protecting target cells against bacterial pore-forming toxins
In spite of their homology—50% identity on the amino acid level—it is conceivable that phobalysin P (PhlyP) and Vibrio cholerae cytolysin (VCC) exert different effects on target cells
PhlyP, in contrast to the closely related VCC, caused fulminant breakdown of membrane integrity but permitted resealing by a process which until now has only been implicated in the repair of much larger membrane lesions, for instance, pores formed by cholesterol-dependent cytolysins

Summary

Introduction

Membrane repair emerges as an innate defense protecting target cells against bacterial pore-forming toxins. The data reveal divergent strategies evolved by two related small ␤-pore-forming toxins to manipulate target cells: phobalysin leads to fulminant perturbation of ion concentrations, closely followed by Ca2ϩ influx-dependent membrane repair. Recovery from attack by the small ␤-pore-forming Staphylococcus aureus alpha-toxin or aerolysin is slow in comparison and does not depend on extracellular Ca2ϩ. To further elucidate the scope of Ca2ϩ influx-dependent repair and understand its limitations, we compared the cellular responses to phobalysin and V. cholerae cytolysin, two related small ␤-pore-forming toxins which create membrane pores of slightly different sizes. We have investigated cellular responses to phobalysin P (PhlyP) and the orthologous Vibrio cholerae cytolysin (VCC) [30,31,32,33,34,35], two related small ␤-PFTs of Photobacterium damselae subsp. We exploited the similar, yet distinct structures of these toxins to gain insight into the function or failure of Ca2ϩ influx-dependent repair after attack by small ␤-PFTs

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