SNARE Protein Mimicry by an Intracellular Bacterium

Cédric Delevoye,Agathe Subtil,Michael Nilges,Stéphanie Perrinet,Fabienne Paumet,Alice Dautry-Varsat,Pierre Dehoux

doi:10.1371/journal.ppat.1000022

Cédric Delevoye, Agathe Subtil + Show 5 more

Open Access

https://doi.org/10.1371/journal.ppat.1000022

Copy DOI

Abstract

Many intracellular pathogens rely on host cell membrane compartments for their survival. The strategies they have developed to subvert intracellular trafficking are often unknown, and SNARE proteins, which are essential for membrane fusion, are possible targets. The obligate intracellular bacteria Chlamydia replicate within an intracellular vacuole, termed an inclusion. A large family of bacterial proteins is inserted in the inclusion membrane, and the role of these inclusion proteins is mostly unknown. Here we identify SNARE-like motifs in the inclusion protein IncA, which are conserved among most Chlamydia species. We show that IncA can bind directly to several host SNARE proteins. A subset of SNAREs is specifically recruited to the immediate vicinity of the inclusion membrane, and their accumulation is reduced around inclusions that lack IncA, demonstrating that IncA plays a predominant role in SNARE recruitment. However, interaction with the SNARE machinery is probably not restricted to IncA as at least another inclusion protein shows similarities with SNARE motifs and can interact with SNAREs. We modelled IncA's association with host SNAREs. The analysis of intermolecular contacts showed that the IncA SNARE-like motif can make specific interactions with host SNARE motifs similar to those found in a bona fide SNARE complex. Moreover, point mutations in the central layer of IncA SNARE-like motifs resulted in the loss of binding to host SNAREs. Altogether, our data demonstrate for the first time mimicry of the SNARE motif by a bacterium.

Highlights

Chlamydia are obligate intracellular bacterial pathogens of eukaryotic cells
As central regulators of membrane fusion, SNARE proteins appear as possible targets for intracellular organisms, which often rely on subverting the host intracellular traffic
Chlamydiae are obligate intracellular bacteria that have coevolved with eukaryotic cells and adapted to a wide range of hosts, causing several diseases in humans and animals

Summary

Introduction

Chlamydia are obligate intracellular bacterial pathogens of eukaryotic cells. They infect a variety of animals, including humans, and cause acute and chronic diseases [1,2,3]. Several lines of evidence indicate a contribution of host cell compartments to the inclusion growth [8,9,10] They suggest that Chlamydiae control their interactions with the host intracellular traffic, allowing some fusion events while avoiding others. SNARE (soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptors) proteins play an essential role in compartment fusion [11]. We have previously shown that one Chlamydia inclusion protein might interact with itself to form a complex similar to that of the SNARE complex, and facilitate the homotypic fusion of inclusions [15] This finding led us to hypothesize that one of the functions of some inclusion proteins is to control intracellular trafficking by mimicking SNAREs. Identification of SNARE-like motifs in IncA and in other C. trachomatis inclusion proteins by bioinformatics.

Author Summary

Findings

Materials and Methods