GroEL/ES inhibitors as potential antibiotics

Abstract

We recently reported results from a high-throughput screening effort that identified 235 inhibitors of the Escherichia coli GroEL/ES chaperonin system [Bioorg. Med. Chem. Lett.2014, 24, 786]. As the GroEL/ES chaperonin system is essential for growth under all conditions, we reasoned that targeting GroEL/ES with small molecule inhibitors could be a viable antibacterial strategy. Extending from our initial screen, we report here the antibacterial activities of 22 GroEL/ES inhibitors against a panel of Gram-positive and Gram-negative bacteria, including E. coli, Bacillus subtilis, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae. GroEL/ES inhibitors were more effective at blocking the proliferation of Gram-positive bacteria, in particular S. aureus, where lead compounds exhibited antibiotic effects from the low-μM to mid-nM range. While several compounds inhibited the human HSP60/10 refolding cycle, some were able to selectively target the bacterial GroEL/ES system. Despite inhibiting HSP60/10, many compounds exhibited low to no cytotoxicity against human liver and kidney cell lines. Two lead candidates emerged from the panel, compounds 8 and 18, that exhibit >50-fold selectivity for inhibiting S. aureus growth compared to liver or kidney cell cytotoxicity. Compounds 8 and 18 inhibited drug-sensitive and methicillin-resistant S. aureus strains with potencies comparable to vancomycin, daptomycin, and streptomycin, and are promising candidates to explore for validating the GroEL/ES chaperonin system as a viable antibiotic target.

Serological Testing for Mycobacterial Heat Shock Protein Hsp65 Antibody in Health and Diseases

“…Sequencing of Hsp65 genes within a family of mycobacteria can be used for sub-classification of mycobacterial species [3][4][5]. In bacterial species, Hsp65 is known as GroEL, and the human homologue is known as human Hsp60, with similar molecular functions in both bacterial and human cells [6,7]. Previous studies demonstrated the presence of anti-Hsp65 antibodies within the circulation of patients with a variety of chronic conditions, including autoimmune diseases such as multiple sclerosis (MS), systemic lupus erythematosus (SLE), and Crohn's disease (CD), as well as other chronic conditions such as heart disease, atherosclerosis, and different types of cancers [8][9][10][11].…”

Targeting the HSP60/10 chaperonin systems of Trypanosoma brucei as a strategy for treating African sleeping sickness

“…33 We have since found that several of our chaperonin inhibitors exhibit antibiotic effects against Gram-positive and Gram-negative bacteria. 35 One of the most potent GroEL/ES inhibitors that we discovered was compound 1 (Figure 3), which inhibited both the substrate refolding and ATPase functions of the chaperonin system. 33,35 Unfortunately, compound 1 was inactive against the panel of bacteria we tested against, suggesting it may not be a good candidate for antibacterial development.…”

“…35 One of the most potent GroEL/ES inhibitors that we discovered was compound 1 (Figure 3), which inhibited both the substrate refolding and ATPase functions of the chaperonin system. 33,35 Unfortunately, compound 1 was inactive against the panel of bacteria we tested against, suggesting it may not be a good candidate for antibacterial development. 35 However, we found a related analog in the PubChem database where the benzimidazole core is replaced by a benzoxazole (Figure 3, compound 2e-p, PubChem CID #1098316).…”

“…33,35 Unfortunately, compound 1 was inactive against the panel of bacteria we tested against, suggesting it may not be a good candidate for antibacterial development. 35 However, we found a related analog in the PubChem database where the benzimidazole core is replaced by a benzoxazole (Figure 3, compound 2e-p, PubChem CID #1098316). 34 While compound 2e-p has been evaluated in 285 assays, it was reported to be active in only 8 bioassays, suggesting this scaffold may be inherently selective and thus a promising candidate to explore for further drug development.…”

“…41 From our previous antibacterial testing, we found that compound 1 exhibited moderate cytotoxicity to human liver (THLE-3) and kidney (HEK 293) cell lines in an established cell culture assay that measures compound cytotoxicity over a 72 h time course. 35 Therefore, in the present study, we developed a set of analogs to try to enhance their anti-parasitic effects against T. brucei while reducing off-target cytotoxicity to human liver and kidney cells. We synthesized two series of compound 1 analogs through simple coupling of sulfonyl chlorides with the 5-amino-2-(4aminophenyl)benzoxazole core (Scheme 1).…”