ABSTRACT
The lead optimization of a series of potent azaindole IKK2 inhibitors is described. Optimization of the human whole blood activity and selectivity over IKK1 in parallel led to the discovery of 16, a potent and selective IKK2 inhibitor showing good efficacy in a rat model of neutrophil activation.
Subject(s)
I-kappa B Kinase/antagonists & inhibitors , Indoles/chemistry , Protein Kinase Inhibitors/chemistry , Animals , Biological Availability , Disease Models, Animal , Half-Life , Humans , I-kappa B Kinase/metabolism , Indoles/chemical synthesis , Indoles/pharmacokinetics , Lung/metabolism , Neutrophils/immunology , Neutrophils/metabolism , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/pharmacokinetics , Rats , Structure-Activity RelationshipABSTRACT
A high-throughput RapidFire mass spectrometry assay is described for the JMJD2 family of Fe(2+), O(2), and α-ketoglutarate-dependent histone lysine demethylases. The assay employs a short amino acid peptide substrate, corresponding to the first 15 amino acid residues of histone H3, but mutated at two positions to increase assay sensitivity. The assay monitors the direct formation of the dimethylated-Lys9 product from the trimethylated-Lys9 peptide substrate. Monitoring the formation of the monomethylated and des-methylated peptide products is also possible. The assay was validated using known inhibitors of the histone lysine demethylases, including 2,4-pyridinedicarboxylic acid and an α-ketoglutarate analogue. With a sampling rate of 7 s per well, the RapidFire technology permitted the single-concentration screening of 101 226 compounds against JMJD2C in 10 days using two instruments, typically giving Z' values of 0.75 to 0.85. Several compounds were identified of the 8-hydroxyquinoline chemotype, a known series of inhibitors of the Lys9-specific histone demethylases. The peptide also functions as a substrate for JMJD2A, JMJD2D, and JMJD2E, thus enabling the development of assays for all 3 enzymes to monitor progress in compound selectivity. The assay represents the first report of a RapidFire mass spectrometry assay for an epigenetics target.
Subject(s)
Drug Evaluation, Preclinical/methods , Enzyme Inhibitors/pharmacology , High-Throughput Screening Assays/methods , Histone Demethylases/metabolism , Jumonji Domain-Containing Histone Demethylases/metabolism , Mass Spectrometry/methods , Dose-Response Relationship, Drug , Enzyme Inhibitors/metabolism , Epigenesis, Genetic/drug effects , Histone Demethylases/antagonists & inhibitors , Jumonji Domain-Containing Histone Demethylases/antagonists & inhibitors , Kinetics , Lysine/metabolism , Oxyquinoline/metabolism , Oxyquinoline/pharmacology , Peptides/metabolism , Pyridines/metabolism , Pyridines/pharmacology , Substrate SpecificityABSTRACT
Polyether ionophores, such as monensin A, are known to be biosynthesised, like many other antibiotic polyketides, on giant modular polyketide synthases (PKSs), but the intermediates and enzymes involved in the subsequent steps of oxidative cyclisation remain undefined. In particular there has been no agreement on the mechanism and timing of the final polyketide chain release. We now report evidence that MonCII from the monensin biosynthetic gene cluster in Streptomyces cinnamonensis, which was previously thought to be an epoxide hydrolase, is a novel thioesterase that belongs to the alpha/beta-hydrolase structural family and might catalyse this step. Purified recombinant MonCII was found to hydrolyse several thioester substrates, including an N-acetylcysteamine thioester derivative of monensin A. Further, incubation with a hallmark inhibitor of such enzymes, phenylmethanesulfonyl fluoride, led to inhibition of the thioesterase activity and to the accumulation of an acylated form of MonCII. These findings require a reassessment of the role of other enzymes implicated in the late stages of polyether ionophore biosynthesis.
