Identification of Aminopyrimidine-Sulfonamides as Potent Modulators of Wag31-mediated Cell Elongation in Mycobacteria

There is an urgent need to discover new anti-tubercular agents with novel mechanisms of action in order to tackle the scourge of drug-resistant tuberculosis. Here, we report the identification of such a molecule – an AminoPYrimidine-Sulfonamide (APYS1) that has potent, bactericidal activity against M. tuberculosis. Mutations in APYS1-resistant M. tuberculosis mapped exclusively to wag31, a gene that encodes a scaffolding protein thought to orchestrate cell elongation. Recombineering confirmed that a Gln201Arg mutation in Wag31 was sufficient to cause resistance to APYS1, however, neither overexpression nor conditional depletion of wag31 impacted M. tuberculosis susceptibility to this compound. In contrast, expression of the wildtype allele of wag31 in APYS1-resistant M. tuberculosis was dominant and restored susceptibility to APYS1 to wildtype levels. Time-lapse imaging and scanning electron microscopy revealed that APYS1 caused gross malformation of the old pole of M. tuberculosis, with eventual lysis. These effects resembled the morphological changes observed following transcriptional silencing of wag31 in M. tuberculosis. These data show that Wag31 is likely not the direct target of APYS1, but the striking phenotypic similarity between APYS1 exposure and genetic depletion of Wag31 in M. tuberculosis suggests that APYS1 might indirectly affect Wag31 through an as yet unknown mechanism. Here a potent anti-tuberculosis compound is described (APYS1), with resistant isolates carrying clustered mutations in the elongation scaffolding protein: Wag31. Visualisation of the impact of APYS1 on Mycobacterium tuberculosis by microscopy reveals gross malformations of the bacterial pole, a phenomenon similar to that observed upon genetic downregulation of wag31. Further validation demonstrates that APYS1 has an atypical mechanism of action, not directly targeting Wag31, but perhaps an associated protein-protein interaction. This article is protected by copyright. All rights reserved.