Dual-targeting GroEL/ES chaperonin and protein tyrosine phosphatase B (PtpB) inhibitors: A polypharmacology strategy for treating Mycobacterium tuberculosis infections

Current treatments for Mycobacterium tuberculosis infections require long and complicated regimens that can lead to patient non-compliance, increasing incidences of antibiotic-resistant strains, and lack of efficacy against latent stages of disease. Thus, new therapeutics are needed to improve tuberculosis standard of care. One strategy is to target protein homeostasis pathways by inhibiting molecular chaperones such as GroEL/ES (HSP60/10) chaperonin systems. M. tuberculosis has two GroEL homologs: GroEL1 is not essential but is important for cytokine-dependent granuloma formation, while GroEL2 is essential for survival and likely functions as the canonical housekeeping chaperonin for folding proteins. Another strategy is to target the protein tyrosine phosphatase B (PtpB) virulence factor that M. tuberculosis secretes into host cells to help evade immune responses. In the present study, we have identified a series of GroEL/ES inhibitors that inhibit M. tuberculosis growth in liquid culture and biochemical function of PtpB in vitro. With further optimization, such dual-targeting GroEL/ES and PtpB inhibitors could be effective against all stages of tuberculosis – actively replicating bacteria, bacteria evading host cell immune responses, and granuloma formation in latent disease – which would be a significant advance to augment current therapeutics that primarily target actively replicating bacteria.     

Hydrolysis of polyphosphates by corn roots

Summary The hydrolysis of seven linear oligomers (P₂, P₃, P₅, P₁₅, P₂₅, P₃₅ and P₆₅) and one cyclic polyphosphate, trimetaphosphate (TMP), by corn (Zea mays) roots was investigated. In these experiments, corn-root homogenate or intact roots were incubated in a polyphosphate solution containing 1 mM polyphosphate or 50 mg P/L, respectively, and the amount of orthophosphate produced was determined. Results showed that the optimal pH value for hydrolysis of P₃, P₅, and TMP by corn-root homogenate was 5.0, whereas for the hydrolysis of P₂, P₁₅, P₂₅, P₃₅ and P₆₅, it was 6.0. The rate of polyphosphate hydrolysis by cornroot homogenate was temperature dependent up to the point of enzyme inactivation (>50°C). Nonsterile intact roots showed higher rates of hydrolysis than sterile roots, especially with P₂. The hydrolysis of all oligomers by sterile and nonsterile intact roots was very slow during the first 18h at 30°C, but increased rapidly after 18h with the oligomers P≦25. The oligomers P₃₅ and P₆₅ were quite resistant to hydrolysis by sterile and nonsterile roots after 48h incubation at 30°C. An experiment with sterile intact roots in pyrophosphate solution suggested that pyrophosphatase was induced in corn roots in the presence of its substrate. The order of hydrolysis rates of the oligomers by intact sterile corn roots was: P₂>P₃>P₅> TMP>P₁₅>P₂₅>P₃₅>P₆₅.