Mycoplasma pneumoniae Community-Acquired Respiratory Distress Syndrome Toxin Uses a Novel KELED Sequence for Retrograde Transport and Subsequent Cytotoxicity.

Kumaraguruparan Ramasamy,Lavanya Pandranki,Krishnan Manickam,Sowmya Balasubramanian,P John Hart,Joel B Baseman,T R Kannan,Alexander B Taylor,R John Collier

doi:10.1128/mbio.01663-17

Kumaraguruparan Ramasamy, Lavanya Pandranki + Show 7 more

Open Access

https://doi.org/10.1128/mbio.01663-17

Copy DOI

Abstract

ABSTRACTMycoplasma pneumoniae is an atypical bacterium that causes respiratory illnesses in humans, including pharyngitis, tracheobronchitis, and community-acquired pneumonia (CAP). It has also been directly linked to reactive airway disease, asthma, and extrapulmonary pathologies. During its colonization, M. pneumoniae expresses a unique ADP-ribosylating and vacuolating cytotoxin designated community-acquired respiratory distress syndrome (CARDS) toxin. CARDS toxin persists and localizes in the airway in CAP patients, asthmatics, and trauma patients with ventilator-associated pneumonia. Although CARDS toxin binds to specific cellular receptors, is internalized, and induces hyperinflammation, histopathology, mucus hyperplasia, and other airway injury, the intracellular trafficking of CARDS toxin remains unclear. Here, we show that CARDS toxin translocates through early and late endosomes and the Golgi complex and concentrates at the perinuclear region to reach the endoplasmic reticulum (ER). Using ER-targeted SNAP-tag, we confirmed the association of CARDS toxin with the ER and determined that CARDS toxin follows the retrograde pathway. In addition, we identified a novel CARDS toxin amino acid fingerprint, KELED, that is required for toxin transport to the ER and subsequent toxin-mediated cytotoxicity.

Highlights

IMPORTANCE Mycoplasma pneumoniae, a leading cause of bacterial communityacquired pneumonia (CAP) among children and adults in the United States, synthesizes a 591-amino-acid ADP-ribosylating and vacuolating protein, designated communityacquired respiratory distress syndrome (CARDS) toxin
HeLa cells were treated with community-acquired respiratory distress syndrome (CARDS) toxin for designated time periods (15 to 120 min) to evaluate its early endosomal association using antibodies reactive against early endosome antigen 1 (EEA1)
Considerable progress has been made in defining the routes by which microbial toxins are delivered to the endoplasmic reticulum (ER), and here, we describe how the M. pneumoniae CARDS toxin reaches the ER via its unique KELED motif

Summary

Introduction

IMPORTANCE Mycoplasma pneumoniae, a leading cause of bacterial communityacquired pneumonia (CAP) among children and adults in the United States, synthesizes a 591-amino-acid ADP-ribosylating and vacuolating protein, designated communityacquired respiratory distress syndrome (CARDS) toxin. In order to elicit its ADP-ribosylating and vacuolating activities, CARDS toxin must bind to host cell receptors, be internalized via clathrin-mediated pathways, and subsequently be transported to specific intracellular organelles. We further showed that CARDS toxin induces interleukin-1␤ (IL-1␤) release upon ADP-ribosylation of NLRP3, a major inflammasome protein [13] Consistent with this observation, we recently reported the role of NLRP3 as a critical mediator of inflammation during M. pneumoniae infection [14]. Other bacterial toxins, including Shiga toxin (ST), CT, and Escherichia coli heat-labile enterotoxin (LT), utilize the retrograde transport pathway to reach the endoplasmic reticulum (ER) [26,27,28]

Methods

Results

Conclusion