Allosteric Probes for Modulating Essential Bacterial Chaperone-Cofactor Interactions.

DnaK is the bacterial homolog of Hsp70, an ATP-dependent chaperone that assists cofactor proteins to catalyze nascent protein folding and salvage misfolded proteins. In the pathogen Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), DnaK and its cofactor proteins DnaJ1, DnaJ2 and GrpE are proposed drug targets. Despite the importance of chaperone function in human cancers and infectious disease, there are limited chemical probes or inhibitors that enable in vivo studies on the function of individual chaperones/cofactors. Here, we describe the discovery of small molecule inhibitors of mycobacterial DnaK from a re-purposed drug library, most notably a peptidomimetic called telaprevir, which is able to inhibit chaperone function through interactions with the peptide-binding cleft of DnaK. Binding of telaprevir leads to allosteric conformational changes that prevent ATP hydrolysis in a distal domain. We find that telaprevir also inhibits E. coli DnaK and human Hsp70 chaperones due to high conservation of Hsp70 sequences. Using in vitro and in vivo chaperone assays, we demonstrate that telaprevir modulates the function of mycobacterial DnaK and its cofactor protein DnaJ2 in cells, which disrupts cellular proteostasis. Co-treatment of mycobacteria with telaprevir and aminoglycosides, which further stress the proteome, enhances the potency of these antibiotics. In addition, telaprevir combats mycobacterial resistance to the frontline TB drug rifampin, as DnaK-DnaJ2 function is required for stabilization of protein mutants that confer drug tolerance. This work sets the stage for the design of peptide-based inhibitors with higher selectivity for bacterial chaperones to probe chaperone-protein interactions and explore resulting synergy with different classes of antibiotics.