Biophysical Society Thematic Meeting - November 16-20, 2015

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Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Speaker Abstracts
22
Identifying Vulnerable Steps in the CoA Biosynthesis Pathway of M. Tuberculosis
Joanna Evans1, Hyungjin Eoh2, Carolina Trujillo2, Sabine Ehrt2, Dirk Schnappinger 2, Helena
Boshoff3, Clifton Barry III3, Kyu Rhee2, Valerie Mizrahi1.
1University of Cape Town, Observatory, Cape Town, South Africa, 2Weill Cornell Medical
College, New York, NY, USA, 3NIAID, Bethesda, MD, USA.
Enzymes in the pantothenate and coenzyme A (CoA) biosynthesis pathways have attracted
considerable interest as potential targets for the development of drugs against a number of human
pathogens, including M. tuberculosis. However, although potent inhibitors have been developed
against pantothenate synthase (PanC), pantothenate kinase (PanK), these have failed to translate
into compounds with significant whole-cell activity. In addition to issues of permeability,
metabolism and efflux, such target-led approaches to TB drug discovery are confounded by a
lack of understanding of target vulnerability.
In this talk, I will describe the combined genetic, physiologic and metabolomic approach we
have taken to identify vulnerable steps in the pantothenate and CoA biosynthesis pathway in M.
tuberculosis. The impact of target depletion on the viability of M. tuberculosis has been assessed
using a set of conditional mutants in various steps in the pathway. While transcriptional silencing
of panB, panC or coaE was bacteriostatic, coaBC silencing was apparently bactericidal in M.
tuberculosis in vitro, as deduced by CFU enumeration. CoaBC was similarly shown to be
required for growth and persistence of M. tuberculosis in mice, based on quantification of organ
bacillary loads. However, taking advantage of the fact that M. tuberculosisis capable of CoaBC
bypass through CoA salvage, we showed that coaBC silencing results in a ‘non-growing but
metabolically active’ (NGMA) state from which non-culturable bacilli can be partially and
transiently rescued by CoA salvage. The response of M. tuberculosis to CoA depletion is being
further explored by metabolomic analyses which have elucidated similarities and differences in
the way in which the organism adapts metabolically to depletion of different targets in the
biosynthetic pathway. These findings have significant implications for TB drug discovery, which
will be discussed.