Autophagy and endosomal trafficking inhibition by Vibrio cholerae MARTX toxin phosphatidylinositol-3-phosphate-specific phospholipase A1 activity.

Shivani Agarwal,Rebecca Williamson,Wonhwa Cho,Gilbert Di Paolo,Shivangi Agarwal,Robin B Chan,Karla J F Satchell,Hyunjin Kim

doi:10.1038/ncomms9745

Shivani Agarwal, Rebecca Williamson + Show 6 more

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https://doi.org/10.1038/ncomms9745

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Abstract

Vibrio cholerae, responsible for acute gastroenteritis secretes a large multifunctional-autoprocessing repeat-in-toxin (MARTX) toxin linked to evasion of host immune system, facilitating colonization of small intestine. Unlike other effector domains of the multifunctional toxin that target cytoskeleton, the function of alpha-beta hydrolase (ABH) remained elusive. This study demonstrates that ABH is an esterase/lipase with catalytic Ser–His–Asp triad. ABH binds with high affinity to phosphatidylinositol-3-phosphate (PtdIns3P) and cleaves the fatty acid in PtdIns3P at the sn1 position in vitro making it the first PtdIns3P-specific phospholipase A1 (PLA1). Expression of ABH in vivo reduces intracellular PtdIns3P levels and its PtdIns3P-specific PLA1 activity blocks endosomal and autophagic pathways. In accordance with recent studies acknowledging the potential of extracellular pathogens to evade or exploit autophagy to prevent their clearance and facilitate survival, this is the first report highlighting the role of ABH in inhibiting autophagy and endosomal trafficking induced by extracellular V. cholerae.

Highlights

The diarrhoeal disease cholera is caused by the ingestion of food or water contaminated with the Gram-negative bacterium Vibrio cholerae through the action of the ADP-ribosylating cholera toxin[1]
In addition to cholera toxin, V. cholerae El Tor O1, the predominating strain variant responsible for cholera over the past 50 years, secretes a number of accessory toxins and proteases, including the multifunctional-autoprocessing repeats-in-toxin toxin (MARTX)[2]. This and other accessory toxins have been linked to enhanced colonization of the small intestine by facilitating evasion of host innate immune cells during early stages of bacterial infection[3,4] The 4,545 amino acid MARTX toxin is secreted from the bacteria and at least partially translocated across the eukaryotic cell plasma membrane where it delivers three effector domains by induced autoprocessing[5,6,7]
The third effector domain of MARTXVc, the a/b-hydrolase (ABH), has been identified as an effector domain independently released from the MARTXVc holotoxin by the cysteine protease domain (CPD)-mediated autoprocessing[5,7] and by sequence homology to a/b-hydrolase family members[13]

Summary

Introduction

The diarrhoeal disease cholera is caused by the ingestion of food or water contaminated with the Gram-negative bacterium Vibrio cholerae through the action of the ADP-ribosylating cholera toxin[1]. In addition to cholera toxin, V. cholerae El Tor O1, the predominating strain variant responsible for cholera over the past 50 years, secretes a number of accessory toxins and proteases, including the multifunctional-autoprocessing repeats-in-toxin toxin (MARTX)[2] This and other accessory toxins have been linked to enhanced colonization of the small intestine by facilitating evasion of host innate immune cells during early stages of bacterial infection[3,4] The 4,545 amino acid (aa) MARTX toxin is secreted from the bacteria and at least partially translocated across the eukaryotic cell plasma membrane where it delivers three effector domains by induced autoprocessing[5,6,7]. The MARTX toxin effector domain ABH represents a novel mechanism by which bacteria evade the host response to infection

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