Mycobacterial PDIM/PGL: synthesis pathway and inhibition

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Mycobacterium tuberculosis (Mt),the etiologic agent of tuberculosis (TB),is a pathogen with a serious impact on global public health and a potential agent for bioterrorism. Mt spreads by airborne droplets and inhalation of 1-10bacteria is sufficient to produce an infection that can result in symptomatic disease. The Center for Disease Control has included multiple-drug resistant (MDR) Mt in Category C of biological agents for public health preparedness against bioterrorism. MDR TB is considered an emerging infectious disease.. The mortality rate of untreatable MDR TB is 40-60%. The threat of MDR TB outbreaks resistant to all current anti-TB drugs, resulting either from natural emergence or bioterrorism, is an alarming scenario. Public health preparedness against MDR TB requires development of new chemotherapies against conventional and unconventional Mt targets to kill the bacterium or impair its virulence or growth in the host. Mt enzymes needed for synthesis of lipids and glycolipids required for virulence are targets for alternative drugs, which alone or in combination therapies, will be useful in prophylaxisand treatment of MDR TB. Such drugs will represent an important line of biodefense in the event of outbreaks of unstoppable Mt infections resistant to all conventional available antibiotics. Elucidation of the biosynthesis of these Mt lipids/glycolipids is an important step towards accelerating development of such drugs. Recent studies revealed that a group of cell-envelope-localized Mt lipids (referred to as PDIMs) is required for full virulence in animal infection models. Production of PDIM-related glycolipids (referred to as PGLs) was recently demonstrated to be responsible for Mt hypervirulent phenotype in a mouse model. Additional studies indicate that PGLs and PDIMs are involved in pathways that counteract host immune mechanisms. These facts suggest that PDIMs and PGLs (collectively referred to as DPKs) play an important role in TB pathogenesis. The proposed studies will investigated several hypothesized steps in DPK synthesis and explore the development of a first PGL synthesis inhibitor. The knowledge gained will provide important insight into DPK synthesis and reveal avenues for development of DPK synthesis inhibitors that will serve as valuable lead compounds in the development of novel anti-TB drugs and tools to decipher the relevance of DPK at specific stages of infection since they could be used to temporally control DPK synthesis in animal models.