Mycobacterium tuberculosis (Mtb) is an extraordinarily successful pathogen that infects 8.6 million people yearly and causes 1.3 million deaths. The principal host cell of Mtb is the lung macrophage (M?). It is not well understood how in some cases the internalized Mtb remain sequestered and are ultimately killed and in other cases persist and escape recognition by the immune system. We have shown that membrane repair mechanisms are extremely important in determining the outcome of infection. Membrane repair maintains the integrity of the M? plasma membrane after infection of M? with avirulent Mtb, a requisite step for apoptosis of infected M?, which kills the pathogen. Virulent Mtb, in contrast, block membrane repair and instead actively induce necrosis, supporting spread of infection and escape from immune control. Mechanistically both avirulent and virulent Mtb induce microdisruptions of the host M? plasma membrane. These plasma membrane lesions are repaired in M? infected with avirulent Mtb, but in the case of virulent Mtb, necrosis ensues because the bacillus inhibits plasma membrane repair. The goal of this project is the delineation of membrane repair in Mtb-infected M?, which will lead to increased understanding of the protective host response mechanism and of the critical steps, by which virulent Mtb escape host containment. A major component of the membrane repair mechanism is Arl8b, a small GTPase involved in lysozyme motility and trafficking.
In Aim 1 we will use a cell line model (HeLa cells) to (a) determine the role of Arl8b and (b) identify additional interacting effector molecules in plasma membrane repair.
In Aim 2 we will test whether Arl8b and the validated effectors are required for plasma membrane repair of Mtb-infected M? and whether virulent Mtb subverts their function. The described studies are directed towards therapeutic interventions to enhance the host anti-mycobacterial response (host-directed tuberculosis therapy).
Mycobacterium tuberculosis (Mtb) is the second most fatal pathogen worldwide after HIV causing 1.4 million deaths per year. Mtb infection is a very serious threat as a consequence of HIV infection and the recurrent emergence of drug resistant strains. During cell infection, Mtb interferes with host intracellular transport to promote its virulence. The project investigates the role of the key trafficking protein Arl8b that controls the trafficking pathways hijacked by Mtb. The understanding of the mechanisms established by Mtb to subvert intracellular transport would provide new insights for the development of new therapeutic strategies.
| Michelet, Xavier; Tuli, Amit; Gan, Huixian et al. (2018) Lysosome-Mediated Plasma Membrane Repair Is Dependent on the Small GTPase Arl8b and Determines Cell Death Type in Mycobacterium tuberculosis Infection. J Immunol 200:3160-3169 |
| Encarnação, Marisa; Espada, Lília; Escrevente, Cristina et al. (2016) A Rab3a-dependent complex essential for lysosome positioning and plasma membrane repair. J Cell Biol 213:631-40 |
| Divangahi, Maziar; Chen, Minjian; Gan, Huixian et al. (2009) Mycobacterium tuberculosis evades macrophage defenses by inhibiting plasma membrane repair. Nat Immunol 10:899-906 |
