Mycobacterium tuberculosis (Mtb) is a human pathogen of worldwide significance. Despite the global and domestic importance of Mtb, we do not have a full understanding of key processes in tuberculosis (TB) pathogenesis. This includes the intracellular survival of Mtb in infected macrophages, progression to active disease vs. latent Mtb infection, persistent patterns of active disease in TB patients even after successful chemotherapy, and excessive lung damage with long-term consequences. These issues are further complicated by HIV-Mtb co-pathogenesis and multidrug-resistant Mtb. While progress has been made in development of new Mtb antibiotic regimens, less conventional approaches including host-directed therapies (HDT) are currently being considered including autophagy-based HDT. Understanding the role and mechanisms of autophagy in control of TB has been, and remains, the central topic of our program. In this project, we look beyond the yeast-centric core ATG genes, the focus of many studies to date. We propose a paradigm shift to focus instead on mammalian systems and unique human autophagy factors and to close the significant knowledge gap in this area. Our long-term goal is to delineate how human/mammalian autophagy factors protect against Mtb infection, control associated cellular damage, and prevent excessive inflammation and tissue destruction. In this project we will define the molecular entities that conduct autophagic control of intracellular Mtb, minimize damage to human cells, and prevent cascading inflammation and tissue destruction. The focus is on two classes of human/mammalian regulators of autophagy: (i) the tripartite motif-containing (TRIM) proteins, represented by TRIM16, in combination with pattern recognition receptors termed Galectins and their interactors, and (ii) immunity-related GTPases, represented specifically by human IRGM and effectors that it controls. We hypothesize that these factors play key roles in organizing the human autophagic apparatus that protects us against Mtb. The project has the following specific aims:
Specific Aim 1. Determine how the mammalian autophagic apparatus recognizes phagosomal damage caused by virulent Mtb and how this contributes to autophagic control of Mtb. We will delineate the role of Galectins and TRIMs in recognizing intracellular Mtb and determine how they orchestrate mammalian autophagic machinery and cell-protective responses.
Specific Aim 2. Define the mechanism of human IRGM action in autophagic maturation and in control of the autophagosomal-lysosomal system in response to intracellular Mtb. We will delineate the IRGM- directed molecular mechanisms of autophagosomal-lysosomal fusion in Mtb infected macrophages. We will determine how the HIV factor Nef impairs IRGM's capacity to orchestrate autophagic maturation and prevents activation of TFEB, a master regulator of the autophagosomal-lysosomal system in human cells.
Tuberculosis remains an utmost public health concern globally and?based on recent and past outbreaks? domestically as well. Escalating public health threats include a relentless global increase in multi-drug- resistance, emergence of extremely-drug-resistant, and even totally-drug-resistant Mycobacterium tuberculosis, the causative agent of tuberculosis. The co-epidemic of tuberculosis and HIV/AIDS further adds complexity to public health control. In this proposal, we seek to harness the powerful process called autophagy, present in every cell in the body. We have recently discovered that, not only does autophagy clear the intracellular bacteria, but it also protects against M. tuberculosis activities that cause the highly transmissible clinical disease. To unleash this internal power that our cells possess, we will identify specific proteins and processes carrying out autophagic elimination of M. tuberculosis and suppressing active disease. This will enable us to develop new autophagy-based therapies and drugs to treat tuberculosis.!
|Kumar, Suresh; Jain, Ashish; Farzam, Farzin et al. (2018) Mechanism of Stx17 recruitment to autophagosomes via IRGM and mammalian Atg8 proteins. J Cell Biol 217:997-1013|
|Claude-Taupin, Aurore; Bissa, Bhawana; Jia, Jingyue et al. (2018) Role of autophagy in IL-1? export and release from cells. Semin Cell Dev Biol 83:36-41|
|Kumar, Suresh; Chauhan, Santosh; Jain, Ashish et al. (2017) Galectins and TRIMs directly interact and orchestrate autophagic response to endomembrane damage. Autophagy 13:1086-1087|
|Kimura, Tomonori; Jia, Jingyue; Claude-Taupin, Aurore et al. (2017) Cellular and molecular mechanism for secretory autophagy. Autophagy 13:1084-1085|