Description du projet
Caractérisation du système de sécrétion de type VII chez Mycobacterium abscessus
Mycobacterium abscessus (Mab) est une mycobactérie non tuberculeuse, multirésistante aux médicaments, responsable d’infections pulmonaires et extrapulmonaires acquises en milieu clinique. Mab survit et se multiplie dans les macrophages, comme la M. tuberculosis (Mtb). La virulence de Mtb est médiée par des protéines sécrétées dans les cellules hôtes par le système de sécrétion de type VII (T7SS), ce qui fait de ce système un bon candidat pour le développement d’un traitement. Les T7SS sont codés dans cinq loci génétiques de Mtb, appelés ESX-1 à ESX-5, chaque système jouant un rôle défini dans la cellule. Mab ne possède que deux T7SS: ESX-3 et un ESX-4 totalement intact et fonctionnel, essentiel pour sa survie intracellulaire. Le projet ESX-4 T7SS, financé par l’UE, proposera une étude fonctionnelle et structurelle interdisciplinaire des mécanismes de la sécrétion dans lesquels les T7SS agissent comme médiateurs.
Objectif
Mycobacterium abscessus (Mab) is an opportunistic-multidrug-resistant non-tuberculous mycobacteria responsible for multiple clinically-acquired infections both pulmonary and extrapulmonary. Unlike many rapidly growing mycobacteria (RGM), Mab is able to survive and multiply within macrophages, similar to slow growing mycobacteria (SGM) such as M. tuberculosis (Mtb). In Mtb, five T7SS (ESX-1-5) have been identified and shown to be essential for intracellular survival (ESX-1), virulence (ESX-1 and ESX-5) or growth (ESX-3). T7SS are composed of five protein components essential for function: EccB, EccC, EccD, EccE and MycP. Except for a low-resolution structure of the holo ESX-5 complex from the host lab at 13 Å resolution, no structural data on any T7SS have been published to date, rendering structural work timely and eagerly awaited by relevant communities. Deemed inactive due to its lack of one of the established T7SS components EccE4, ESX-4 has been considered an ancestral T7SS form. However, Mab possess a fully intact and functional ESX-4, essential for its intracellular survival, rendering it a highly attractive target for an in-depth characterization. Here, I propose an interdisciplinary project that includes both functional and structural investigation. As the 2 M Dalton-holo-complex crosses the Mab inner membrane, experimental structural work will be challenging and require an integrative modeling approach to combine diverse experimental data sets. Complementary infection biology experiments including microbiology, genetics and cell biology will be carried out by collaborators. With this work, I aim to respond to central questions related to T7SS in general and Mab ESX-4 specifically, such as: what is the mechanism of T7SS-mediated secretion? What makes ESX-4 specific and different from other T7SS? What is the specific role of EccE4 to establish a functionally active ESX4? and What are the substrates and specific mechanism of ESX-4 substrate recognition?
Champ scientifique
Programme(s)
Régime de financement
MSCA-IF-EF-ST - Standard EFCoordinateur
69117 Heidelberg
Allemagne