title: Upregulation of the phthiocerol dimycocerosate biosynthetic pathway by rifampin-resistant, rpoB mutant Mycobacterium tuberculosis.
abstract: Multidrug-resistant tuberculosis has emerged as a major threat to tuberculosis control. Phylogenetically related rifampin-resistant actinomycetes with mutations mapping to clinically dominant Mycobacterium tuberculosis mutations in the rpoB gene show upregulation of gene networks encoding secondary metabolites. We compared the expressed proteomes and metabolomes of two fully drug-susceptible clinical strains of M. tuberculosis (wild type) to those of their respective rifampin-resistant, rpoB mutant progeny strains with confirmed rifampin monoresistance following antitubercular therapy. Each of these strains was also used to infect gamma interferon- and lipopolysaccharide-activated murine J774A.1 macrophages to analyze transcriptional responses in a physiologically relevant model. Both rpoB mutants showed significant upregulation of the polyketide synthase genes ppsA-ppsE and drrA, which constitute an operon encoding multifunctional enzymes involved in the biosynthesis of phthiocerol dimycocerosate and other lipids in M. tuberculosis, but also of various secondary metabolites in related organisms, including antibiotics, such as erythromycin and rifamycins. ppsA (Rv2931), ppsB (Rv2932), and ppsC (Rv2933) were also found to be upregulated more than 10-fold in the Beijing rpoB mutant strain relative to its wild-type parent strain during infection of activated murine macrophages. In addition, metabolomics identified precursors of phthiocerol dimycocerosate, but not the intact molecule itself, in greater abundance in both rpoB mutant isolates. These data suggest that rpoB mutation in M. tuberculosis may trigger compensatory transcriptional changes in secondary metabolism genes analogous to those observed in related actinobacteria. These findings may assist in developing novel methods to diagnose and treat drug-resistant M. tuberculosis infections.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Bisson
authors.forename: Carolina
authors.initials: C
authors.lastname: Mehaffy
authors.forename: Corey
authors.initials: C
authors.lastname: Broeckling
authors.forename: Jessica
authors.initials: J
authors.lastname: Prenni
authors.forename: Dalin
authors.initials: D
authors.lastname: Rifat
authors.forename: Desmond S
authors.initials: DS
authors.lastname: Lun
authors.forename: Marcos
authors.initials: M
authors.lastname: Burgos
authors.forename: Drew
authors.initials: D
authors.lastname: Weissman
authors.forename: Petros C
authors.initials: PC
authors.lastname: Karakousis
authors.forename: Karen
authors.initials: K
authors.lastname: Dobos
mesh_terms: D000818:Animals; D000995:Antitubercular Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000235:genetics*; D002460:Cell Line; D012321:DNA-Directed RNA Polymerases; D024881:Drug Resistance, Bacterial; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008055:Lipids / Q000096:biosynthesis*; D008264:Macrophages / Q000382:microbiology; D055442:Metabolome; D051379:Mice; D008826:Microbial Sensitivity Tests; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D012293:Rifampin / Q000494:pharmacology*; D014376:Tuberculosis / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D008055:Lipids; D050505:Mutant Proteins; D020543:Proteome; C505805:rpoB protein, Mycobacterium tuberculosis; C008901:phthiocerol dimycocerosate; D012321:DNA-Directed RNA Polymerases; D012293:Rifampin