Repurposing Hsp90 inhibitors as antibiotics targeting histidine kinases.

To address the growing need for new antimicrobial agents, we explored whether inhibition of bacterial signaling machinery could inhibit bacterial growth. Because bacteria rely on two-component signaling systems to respond to environmental changes, and because these systems are both highly conserved and mediated by histidine kinases, inhibiting histidine kinases may provide broad spectrum antimicrobial activity. The histidine kinase ATP binding domain is conserved with the ATPase domain of eukaryotic Hsp90 molecular chaperones.

A cell cycle kinase with tandem sensory PAS domains integrates cell fate cues.

All cells must integrate sensory information to coordinate developmental events in space and time. The bacterium Caulobacter crescentus uses two-component phospho-signalling to regulate spatially distinct cell cycle events through the master regulator CtrA. Here, we report that CckA, the histidine kinase upstream of CtrA, employs a tandem-PAS domain sensor to integrate two distinct spatiotemporal signals.

(p)ppGpp modulates cell size and the initiation of DNA replication in Caulobacter crescentus in response to a block in lipid biosynthesis.

Stress conditions, such as a block in fatty acid synthesis, signal bacterial cells to exit the cell cycle. Caulobacter crescentus FabH is a cell-cycle-regulated β-ketoacyl-acyl carrier protein synthase that initiates lipid biosynthesis and is essential for growth in rich media. To explore how C.

Cell fate regulation governed by a repurposed bacterial histidine kinase.

One of the simplest organisms to divide asymmetrically is the bacterium Caulobacter crescentus. The DivL pseudo-histidine kinase, positioned at one cell pole, regulates cell-fate by controlling the activation of the global transcription factor CtrA via an interaction with the response regulator (RR) DivK. DivL uniquely contains a tyrosine at the histidine phosphorylation site, and can achieve these regulatory functions in vivo without kinase activity.

Branched signal wiring of an essential bacterial cell-cycle phosphotransfer protein.

Vital to bacterial survival is the faithful propagation of cellular signals, and in Caulobacter crescentus, ChpT is an essential mediator within the cell-cycle circuit. ChpT functions as a histidine-containing phosphotransfer protein (HPt) that shuttles a phosphoryl group from the receiver domain of CckA, the upstream hybrid histidine kinase (HK), to one of two downstream response regulators (CtrA or CpdR) that controls cell-cycle progression. To understand how ChpT interacts with multiple signaling partners, we solved the crystal structure of ChpT at 2.

Kinetics of inhibitor cycling underlie therapeutic disparities between EGFR-driven lung and brain cancers.

Unlabelled: Although mutational activation of the epidermal growth factor receptor (EGFR) features prominently in glioma and non-small cell lung cancer (NSCLC), inhibitors of EGFR improve survival only in patients with NCSLC. To understand how mutations in EGFR influence response to therapy, we generated glioma cells expressing either glioma- or NSCLC-derived alleles and quantified kinase-site occupancy by clinical inhibitors with the use of a novel affinity probe and kinetic methodology. At equivalent doses, erlotinib achieved lower kinase-site occupancy in glioma-derived EGFRvIII compared with NSCLC-derived EGFR mutants.

Resiliency and vulnerability in the HER2-HER3 tumorigenic driver.

About 25% of breast cancers harbor the amplified oncogene human epidermal growth factor receptor 2 (HER2) and are dependent on HER2 kinase function, identifying HER2 as a vulnerable target for therapy. However, HER2-HER3 signaling is buffered so that it is protected against a nearly two-log inhibition of HER2 catalytic activity; this buffering is driven by the negative regulation of HER3 by Akt. We have now further characterized HER2-HER3 signaling activity and have shown that the compensatory buffering prevents apoptotic tumor cell death from occurring as a result of the combined loss of mitogen-activated protein kinase (MAPK) and Akt signaling.

Targeted polypharmacology: discovery of dual inhibitors of tyrosine and phosphoinositide kinases.

The clinical success of multitargeted kinase inhibitors has stimulated efforts to identify promiscuous drugs with optimal selectivity profiles. It remains unclear to what extent such drugs can be rationally designed, particularly for combinations of targets that are structurally divergent. Here we report the systematic discovery of molecules that potently inhibit both tyrosine kinases and phosphatidylinositol-3-OH kinases, two protein families that are among the most intensely pursued cancer drug targets.

Structure-guided development of affinity probes for tyrosine kinases using chemical genetics.

As key components in nearly every signal transduction pathway, protein kinases are attractive targets for the regulation of cellular signaling by small-molecule inhibitors. We report the structure-guided development of 6-acrylamido-4-anilinoquinazoline irreversible kinase inhibitors that potently and selectively target rationally designed kinases bearing two selectivity elements that are not found together in any wild-type kinase: an electrophile-targeted cysteine residue and a glycine gatekeeper residue. Cocrystal structures of two irreversible quinazoline inhibitors bound to either epidermal growth factor receptor (EGFR) or engineered c-Src show covalent inhibitor binding to the targeted cysteine (Cys797 in EGFR and Cys345 in engineered c-Src).

Escape from HER-family tyrosine kinase inhibitor therapy by the kinase-inactive HER3.

Oncogenic tyrosine kinases have proved to be promising targets for the development of highly effective anticancer drugs. However, tyrosine kinase inhibitors (TKIs) against the human epidermal growth factor receptor (HER) family show only limited activity against HER2-driven breast cancers, despite effective inhibition of epidermal growth factor receptor (EGFR) and HER2 in vivo. The reasons for this are unclear.