Mechanism of Action of Mycobacterium tuberculosis Gyrase Inhibitors: A Novel Class of Gyrase Poisons

Abstract

Tuberculosis is one of the leading causes of morbidity worldwide, and the incidences of drug resistance and intolerance are prevalent. Thus, there is a desperate need for the development of new antitubercular drugs. Mycobacterium tuberculosis gyrase inhibitors (MGIs) are napthyridone/aminopiperidine-based drugs that display activity against M. tuberculosis cells and tuberculosis in mouse models [Blanco, D., et al. (2015) Antimicrob. Agents Chemother. 59, 1868-1875]. Genetic and mutagenesis studies suggest that gyrase, which is the target for fluoroquinolone antibacterials, is also the target for MGIs. However, little is known regarding the interaction of these drugs with the bacterial type II enzyme. Therefore, we examined the effects of two MGIs, GSK000 and GSK325, on M. tuberculosis gyrase. MGIs greatly enhanced DNA cleavage mediated by the bacterial enzyme. In contrast to fluoroquinolones (which induce primarily double-stranded breaks), MGIs induced only single-stranded DNA breaks under a variety of conditions. MGIs work by stabilizing covalent gyrase-cleaved DNA complexes and appear to suppress the ability of the enzyme to induce double-stranded breaks. The drugs displayed little activity against type II topoisomerases from several other bacterial species, suggesting that these drugs display specificity for M. tuberculosis gyrase. Furthermore, MGIs maintained activity against M. tuberuclosis gyrase enzymes that contained the three most common fluoroquinolone resistance mutations seen in the clinic and displayed no activity against human topoisomerase IIα. These findings suggest that MGIs have potential as antitubercular drugs, especially in the case of fluoroquinolone-resistant disease.

Mechanistic and Structural Basis for the Actions of the Antibacterial Gepotidacin against Staphylococcus aureus Gyrase

“…65–67 This mechanism is consistent with the single-stranded DNA cleavage induced by Mycobacterium tuberculosis gyrase inhibitors (MGIs), which constitute a subclass of NBTIs optimized for activity against M. tuberculosis gyrase. 44…”

“…7, 25, 36–42 However, in contrast to fluoroquinolones, which induce primarily double-stranded DNA breaks, these NBTIs reportedly stabilize primarily enzyme-mediated single stranded breaks. 25, 44…”

Host Bioenergetic Parameters Reveal Cytotoxicity of Antituberculosis Drugs Undetected Using Conventional Viability Assays

“…S3) and do not have similar mechanisms of action on M. tuberculosis ( Table 1 ), which, importantly, suggests that cytotoxic effects cannot be predicted from structure-activity relationships. EMB is thought to inhibit the biosynthesis of the cell wall, by inhibiting arabinosyltransferase required for the synthesis of arabinogalactan and lipoarabinomannan ( 94 ), whereas MXF is a fluoroquinolone that inhibits DNA gyrase that allows the untwisting required to synthesize two DNA helices from one DNA double helix ( 95 ). This is further supported by the effects of INH and RIF on the bioenergetic parameters clustering together in both the THP-1 and hMDM cells, although they are not chemically related (Fig.…”

Host bioenergetic parameters reveal cytotoxicity of anti-tuberculosis drugs undetected using conventional viability assays

“…EMB is thought to inhibit the biosynthesis of the cell wall, by inhibiting arabionsyltransferase required for the synthesis of arabinogalactan and lipoarabinomannan(83), whereas MXF is a fluoroquinolone that inhibits DNA gyrase that allows the untwisting required to synthesize two DNA helices from one DNA double helix (84). This is further supported by the effects of INH and RIF on the bioenergetic parameters clustering together in both the THP-1 and hMDM cells, although they are not chemically related nor have similar mechanisms of action.…”