Project description
Characterisation of type VII secretion system in Mycobacterium abscessus
Mycobacterium abscessus (Mab) is a multidrug-resistant, non-tuberculous mycobacterium responsible for pulmonary and extrapulmonary clinic infections. Mab survives and multiplies within macrophages, similar to M. tuberculosis (Mtb). The Mtb virulence is mediated by proteins secreted into the host cells by the type VII secretion system (T7SS), making this system a candidate for treatment development. The T7SSs are encoded within five genetic loci in Mtb, named ESX-1 to ESX-5, with each system carrying out a defined role within the cell. Mab only possess two T7SS: ESX-3 and a fully intact and functional ESX-4 essential for its intracellular survival. The EU-funded ESX-4 T7SS project proposes an interdisciplinary functional and structural study of the mechanisms of T7SS-mediated secretion.
Objective
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?
Fields of science
Programme(s)
Funding Scheme
MSCA-IF-EF-ST - Standard EFCoordinator
69117 Heidelberg
Germany