Chemoproteomics Reveals the Pan-HER Kinase Inhibitor Neratinib To Target an Arabidopsis Epoxide Hydrolase Related to Phytohormone Signaling.

Plant phytohormone pathways are regulated by an intricate network of signaling components and modulators, many of which still remain unknown. Here, we report a forward chemical genetics approach for the identification of functional SA agonists in Arabidopsis thaliana that revealed Neratinib (Ner), a covalent pan-HER kinase inhibitor drug in humans, as a modulator of SA signaling. Instead of a protein kinase, chemoproteomics unveiled that Ner covalently modifies a surface-exposed cysteine residue of Arabidopsis epoxide hydrolase isoform 7 (AtEH7), thereby triggering its allosteric inhibition. Physiologically, the Ner application induces jasmonate metabolism in an AtEH7-dependent manner as an early response. In addition, it modulates PATHOGENESIS RELATED 1 (PR1) expression as a hallmark of SA signaling activation as a later effect. AtEH7, however, is not the exclusive target for this physiological readout induced by Ner. Although the underlying molecular mechanisms of AtEH7-dependent modulation of jasmonate signaling and Ner-induced PR1-dependent activation of SA signaling and thus defense response regulation remain unknown, our present work illustrates the powerful combination of forward chemical genetics and chemical proteomics for identifying novel phytohormone signaling modulatory factors. It also suggests that marginally explored metabolic enzymes such as epoxide hydrolases may have further physiological roles in modulating signaling.

Identification of the Natural Product Rotihibin†A as a TOR Kinase Signaling Inhibitor by Unbiased Transcriptional Profiling.

Bioactive natural products are important starting points for developing chemical tools for biological research. For elucidating their bioactivity profile, biological systems with concise complexity such as cell culture systems are frequently used, whereas unbiased investigations in more complex multicellular systems are only rarely explored. Here, we demonstrate with the natural product Rotihibin A and the plant research model system Arabidopsis thaliana that unbiased transcriptional profiling enables a rapid, label-free, and compound economic evaluation of a natural product's bioactivity profile in a complex multicellular organism. To this end, we established a chemical synthesis of Rotihibin A as well as that of structural analogues, followed by transcriptional profiling-guided identification and validation of Rotihibin A as a TOR signaling inhibitor (TOR=target of rapamycin). These findings illustrate that a combined approach of transcriptional profiling and natural product research may represent a technically simple approach to streamline the development of chemical tools from natural products even for biologically complex multicellular biological systems.

A Non-Competitive Inhibitor of VCP/p97 and VPS4 Reveals Conserved Allosteric Circuits in Type I and II AAA ATPases.

AAA ATPases have pivotal functions in diverse cellular processes essential for survival and proliferation. Revealing strategies for chemical inhibition of this class of enzymes is therefore of great interest for the development of novel chemotherapies or chemical tools. Here, we characterize the compound MSC1094308 as a reversible, allosteric inhibitor of the type II AAA ATPase human ubiquitin-directed unfoldase (VCP)/p97 and the type I AAA ATPase VPS4B. Subsequent proteomic, genetic and biochemical studies indicate that MSC1094308 binds to a previously characterized drugable hotspot of p97, thereby inhibiting the D2 ATPase activity. Our results furthermore indicate that a similar allosteric site exists in VPS4B, suggesting conserved allosteric circuits and drugable sites in both type I and II AAA ATPases. Our results may thus guide future chemical tool and drug discovery efforts for the biomedically relevant AAA ATPases.

Turning-ON Proteasomes.

While proteasome inhibitors are now well-established research tools and chemotherapeutics, proteasome activators are much less explored. In this issue of Cell Chemical Biology, in a study from the groups of Berkers and Ovaa (Leestemaker et al., 2017), a chemical screen was used to identify a p38 MAPK inhibitor as a proteasome activator. This compound furthermore enhanced clearance of protein aggregates, thereby implicating alternative chemotherapeutic options for treating neurodegenerative diseases.

The Root Growth-Regulating Brevicompanine Natural Products Modulate the Plant Circadian Clock.

Plant growth regulating properties of brevicompanines (Brvs), natural products of the fungus Penicillium brevicompactum, have been known for several years, but further investigations into the molecular mechanism of their bioactivity have not been performed. Following chemical synthesis of brevicompanine derivatives, we studied their activity in the model plant Arabidopsis by a combination of plant growth assays, transcriptional profiling, and numerous additional bioassays. These studies demonstrated that brevicompanines cause transcriptional misregulation of core components of the circadian clock, whereas other biological read-outs were not affected. Brevicompanines thus represent promising chemical tools for investigating the regulation of the plant circadian clock. In addition, our study also illustrates the potential of an unbiased -omics-based characterization of bioactive compounds for identifying the often cryptic modes of action of small molecules.

Negative pressure wound therapy: a vacuum of evidence?

OBJECTIVE: To systematically examine the clinical effectiveness and safety of negative pressure wound therapy (NPWT) compared with conventional wound therapy. DATA SOURCES: MEDLINE, EMBASE, CINAHL, and the Cochrane Library were searched. Manufacturers were contacted, and trial registries were screened. STUDY SELECTION: Randomized controlled trials (RCTs) and non-RCTs comparing NPWT and conventional therapy for acute or chronic wounds were included in this review. The main outcomes of interest were wound-healing variables. After screening 255 full-text articles, 17 studies remained. In addition, 19 unpublished trials were found, of which 5 had been prematurely terminated. DATA EXTRACTION: Two reviewers independently extracted data and assessed methodologic quality in a standardized manner. DATA SYNTHESIS: Seven RCTs (n = 324) and 10 non-RCTs (n = 278) met the inclusion criteria. The overall methodologic quality of the trials was poor. Significant differences in favor of NPWT for time to wound closure or incidence of wound closure were shown in 2 of 5 RCTs and 2 of 4 non-RCTs. A meta-analysis of changes in wound size that included 4 RCTs and 2 non-RCTs favored NPWT (standardized mean difference: RCTs, -0.57; non-RCTs, -1.30). CONCLUSIONS: Although there is some indication that NPWT may improve wound healing, the body of evidence available is insufficient to clearly prove an additional clinical benefit of NPWT. The large number of prematurely terminated and unpublished trials is reason for concern.

Applying evidence-based surgery in daily clinical routine: a feasibility study.

BACKGROUND: Although the word evidence-based medicine (EBM) has gained wide popularity, only a few studies have evaluated how EBM works in clinical practice. METHODS: We have prospectively evaluated the feasibility of evidence-based trauma surgery. Orthopaedic trauma surgeons were asked to produce clinical questions related to the treatment of current patients. An informaticist searched the literature (Medline, Cochrane Library, practice guidelines and textbooks) and reported the findings on every following day. The study's main endpoints were the rate of questions for which relevant evidence (>level V) was available and the time necessary to find and critically appraise medical evidence. RESULTS: In total, 44 EBM questions were formulated, mainly concerning treatment options. PubMed was searched for 39 questions, textbooks for 14, the Cochrane Library for 11, online guidelines for 9 and other sources were used for 4 questions. On average, 157 text items (three per questions) were identified as potentially relevant. Journal articles predominated (83%) over textbooks (10%). Sixty-eight percent of the questions (30 of 44) were answered, either on the basis level 1 (n=13 questions), level 2 (n=6), or level 4 evidence (n=14). Trying to answer a question required 53 min on average, split up between 39 min of database searches and 25 min of obtaining full text articles. In four cases, the evidence suggested a change in clinical management. The physicians were very appreciative of our project and found the provided evidence very helpful for their clinical decisions. CONCLUSIONS: Time will be the main barrier against the introduction of clinical EBM. It is likely that clinicians reduce EBM to those situations where evidence is likely to be found. Although the impact of EBM on patient-care was limited, the concept of EBM was successfully implemented.