title: Targeting intracellular p-aminobenzoic acid production potentiates the anti-tubercular action of antifolates.
abstract: The ability to revitalize and re-purpose existing drugs offers a powerful approach for novel treatment options against Mycobacterium tuberculosis and other infectious agents. Antifolates are an underutilized drug class in tuberculosis (TB) therapy, capable of disrupting the biosynthesis of tetrahydrofolate, an essential cellular cofactor. Based on the observation that exogenously supplied p-aminobenzoic acid (PABA) can antagonize the action of antifolates that interact with dihydropteroate synthase (DHPS), such as sulfonamides and p-aminosalicylic acid (PAS), we hypothesized that bacterial PABA biosynthesis contributes to intrinsic antifolate resistance. Herein, we demonstrate that disruption of PABA biosynthesis potentiates the anti-tubercular action of DHPS inhibitors and PAS by up to 1000 fold. Disruption of PABA biosynthesis is also demonstrated to lead to loss of viability over time. Further, we demonstrate that this strategy restores the wild type level of PAS susceptibility in a previously characterized PAS resistant strain of M. tuberculosis. Finally, we demonstrate selective inhibition of PABA biosynthesis in M. tuberculosis using the small molecule MAC173979. This study reveals that the M. tuberculosis PABA biosynthetic pathway is responsible for intrinsic resistance to various antifolates and this pathway is a chemically vulnerable target whose disruption could potentiate the tuberculocidal activity of an underutilized class of antimicrobial agents.
authors.affiliation: Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Thiede
authors.affiliation: Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Kordus
authors.affiliation: Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Breanna J
authors.initials: BJ
authors.lastname: Turman
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Buonomo
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Courtney C
authors.initials: CC
authors.lastname: Aldrich
authors.affiliation: Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Minato
authors.affiliation: Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Baughn
mesh_terms: D010129:4-Aminobenzoic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D053898:Biosynthetic Pathways / Q000187:drug effects* / Q000235:genetics; D003001:Cloning, Molecular; D058492:Drug Repositioning; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D004357:Drug Synergism; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics*; D054852:Small Molecule Libraries / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D005493:Folic Acid Antagonists; D054852:Small Molecule Libraries; D010129:4-Aminobenzoic Acid