Role of mycobacterial dynamin-like proteins in the biogenesis of membrane vesicles, and host-pathogen interactions

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Despite the widespread use of an attenuated vaccine and several antibiotics, tuberculosis (TB) continues to be a global public health problem. Over 1.2 million people died from TB in 2019. This dire situation is compounded by increasing prevalence of antibiotic resistant strains of Mycobacterium tuberculosis (Mtb), the main etiological agent of human TB. Central to Mtb success is its ability to evade, modulate, and even manipulate host immune defense response. Consequently, bacterial factors involved in undermining the immune system are potentially good targets for TB intervention. Like many other bacteria, Mtb actively produces extracellular vesicles (EVs) in vitro and in vivo. These are membrane enclosed spherical structures that allow the bacteria to concentrate and secrete a variety of molecules, and communicate with other cells in their environment. The release of EVs by Mtb infecting macrophages enables the delivery of pathogenicity factors and immunomodulatory molecules into the host cell, and the extracellular milieu. Strong evidence from in vitro studies indicates that EVs may allow Mtb to remotely influence bystander immune cells. However, the limited understanding of the molecular mechanisms involved in vesicle biogenesis, and the lack of mutants deficient in vesicle production have impeded progress in elucidating the relevance of vesicle secretion to Mtb virulence. Our preliminary work identified the dynamin-like proteins (DLP) of Mtb as essential factors for efficient EVs release and characterized a DLP mutant deficient in vesicle biogenesis. We are now well positioned to dissect DLP's function in vesicle formation and assess the role of EV production during infection, using a mouse model of TB; those are the main goals of this proposal. We anticipate the findings will advance the TB field by highlighting ways to target vesicle release, or disrupt the effects of vesicles in host-resistance to TB.