Animals have evolved defense systems for surviving in a chemically diverse environment. Such systems should demonstrate plasticity, such as adaptive immunity, enabling a response to even unknown chemicals. The antioxidant transcription factor Nrf2 is activated in response to various electrophiles and induces cytoprotective enzymes that detoxify them. We report here the discovery of a multiple sensing mechanism for Nrf2 activation using zebrafish and 11 Nrf2-activating compounds. First, we showed that six of the compounds tested specifically target Cys-151 in Keap1, the ubiquitin ligase for Nrf2, while two compounds target Cys-273. Second, in addition to Nrf2 and Keap1, a third factor was deemed necessary for responding to three of the compounds. Finally, we isolated a zebrafish mutant defective in its response to seven compounds but not in response to the remaining four. These results led us to categorize Nrf2 activators into six classes and hypothesize that multiple sensing allows enhanced plasticity in the system.Nrf2 is a transcription factor that transactivates cytoprotective genes through a common DNA regulatory element, called the antioxidant response element or electrophile response element (18, 24). Nrf2 target genes are multifarious and encode phase 2 detoxifying enzymes, antioxidant proteins, enzymes for glutathione biosynthesis, ABC transporters, scavenger receptors, transcription factors, proteases, chaperone proteins, and so forth (23). Under basal conditions, Nrf2 is rapidly degraded by proteasomes, and little induction of target genes is observed. This degradation is controlled by Keap1, an Nrf2-specific adaptor protein for the Cul3 ubiquitin ligase complex (12,20). Nrf2-activating compounds block Keap1-dependent Nrf2 ubiquitination, leading to the stabilization and nuclear translocation of Nrf2 and subsequent induction of Nrf2 target genes.A number of Nrf2 activators have been found but, interestingly, no common structures were identified among them (23). Talalay and coworkers classified Nrf2-activating compounds into the following 10 distinct classes based on their chemical structures (7): diphenols, Michael reaction acceptors, isothiocyanates, thiocarbamates, trivalent arsenicals, 1,2-dithiole-3-thiones, hydroperoxides, vicinal dimercaptans, heavy metals, and polyenes. A current pursuit is unraveling how cells detect these chemical compounds and transduce their signals into the activation of Nrf2. Keap1 has many highly reactive cysteine residues that have the potential to sense electrophilic Nrf2 activators by forming covalent adducts with them. We and others have therefore proposed the model that Nrf2-activating compounds directly modify the sulfhydryl groups of Keap1 cysteines by oxidation, reduction, or alkylation, which alters the conformation of Keap1 and ceases the ubiquitination of Nrf2 (7,24). In fact, mass spectrometry (MS) studies revealed that some Nrf2-activating compounds can covalently react with cysteines in mouse or human Keap1. For example, dexamethasone 21-mesylate with ; iodo...

The generation of an excitatory receptor current in mammalian olfactory sensory neurons (OSNs) involves the sequential activation of two distinct types of ion channels: cAMP-gated Ca 2ϩ -permeable cation channels and Ca

The synthesis of large single crystals of GaN (gallium nitride) is a matter of great importance in optoelectronic devices for blue-light-emitting diodes and lasers. Although high-quality bulk single crystals of GaN suitable for substrates are desired, the standard method of cooling its stoichiometric melt has been unsuccessful for GaN because it decomposes into Ga and N(2) at high temperatures before its melting point. Here we report that applying high pressure completely prevents the decomposition and allows the stoichiometric melting of GaN. At pressures above 6.0 GPa, congruent melting of GaN occurred at about 2,220 degrees C, and decreasing the temperature allowed the GaN melt to crystallize to the original structure, which was confirmed by in situ X-ray diffraction. Single crystals of GaN were formed by cooling the melt slowly under high pressures and were recovered at ambient conditions.

New strategies for the care of irritable bowel syndrome (IBS) are developing and several novel treatments have been globally produced. New methods of care should be customized geographically because each country has a specific medical system, life style, eating habit, gut microbiota, genes and so on. Several clinical guidelines for IBS have been proposed and the Japanese Society of Gastroenterology (JSGE) subsequently developed evidence-based clinical practice guidelines for IBS. Sixty-two clinical questions (CQs) comprising 1 definition, 6 epidemiology, 6 pathophysiology, 10 diagnosis, 30 treatment, 4 prognosis, and 5 complications were proposed and statements were made to answer to CQs. A diagnosis algorithm and a three-step treatment was provided for patients with chronic abdominal pain or abdominal discomfort and/or abnormal bowel movement. If more than one alarm symptom/sign, risk factor and/or routine examination is positive, colonoscopy is indicated. If all of them, or the subsequent colonoscopy, are/is negative, Rome III or compatible criteria is applied. After IBS diagnosis, step 1 therapy consisting of diet therapy, behavioral modification and guttargeted pharmacotherapy is indicated for four weeks. Nonresponders to step 1 therapy proceed to the second step that includes psychopharmacological agents and simple psychotherapy for four weeks. In the third step, for patients nonresponsive to step 2 therapy, a combination of gut-targeted pharmacotherapy, psychopharmacological treatments and/or specific psychotherapy is/are indicated. Clinical guidelines and consensus for IBS treatment in Japan are well suited for Japanese IBS patients; as such, they may provide useful insight for IBS treatment in other countries around the world.

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The mammalian olfactory system detects an unlimited variety of odorants with a limited set of odorant receptors. To cope with the complexity of the odor world, each odorant receptor must detect many different odorants. The demand for low odor selectivity creates problems for the transduction process: the initial transduction step, the synthesis of the second messenger cAMP, operates with low efficiency, mainly because odorants bind only briefly to their receptors. Sensory cilia of olfactory receptor neurons have developed an unusual solution to this problem. They accumulate chloride ions at rest and discharge a chloride current upon odor detection. This chloride current amplifies the receptor potential and promotes electrical excitation. We have studied this amplification process by examining identity, subcellular localization, and regulation of its molecular components. We found that the Na + /K + /2Cl − cotransporter NKCC1 is expressed in the ciliary membrane, where it mediates chloride accumulation into the ciliary lumen. Gene silencing experiments revealed that the activity of this transporter depends on the kinases SPAK and OSR1, which are enriched in the cilia together with their own activating kinases, WNK1 and WNK4. A second Cl − transporter, the Cl − /HCO 3 − exchanger SLC4A1, is expressed in the cilia and may support Cl − accumulation. The calcium-dependent chloride channel TMEM16B (ANO2) provides a ciliary pathway for the excitatory chloride current. These findings describe a specific set of ciliary proteins involved in anion-based signal amplification. They provide a molecular concept for the unique strategy that allows olfactory sensory neurons to operate as efficient transducers of weak sensory stimuli.chloride | olfaction | sensory transduction | transport | kinase M ammalian olfactory receptor neurons (ORNs) present to the air a tuft of sensory cilia equipped with odorant receptors. Upon contact with odorants, these receptors actuate a transduction cascade that leads to firing of action potentials. This cascade has an unusual, two-stage organization (1). First, the activated odorant receptors induce a rise of the second messengers cAMP and Ca 2+ in the cilia, a process that involves cAMP-gated, Ca 2+ -permeable ion channels. In the second stage, inflowing Ca 2+ opens Cl − channels. By conducting a depolarizing Cl − efflux from the cilia, these channels amplify the receptor potential approximately 10-fold, thus helping to excite the neuron even when stimulation is weak. ORNs accumulate chloride through the Na + /K + /2Cl − cotransporter NKCC1 and maintain an elevated intracellular Cl − concentration (2, 3) to support amplification. Accordingly, gene ablation of NKCC1, as well as the pharmacologic suppression of Cl − accumulation or Cl − efflux, strongly inhibits the sensory response of ORNs (3-5). Although these observations provide a robust concept for signal amplification, several points are still unclear. These concern both the Cl − accumulation process and the excitatory Cl − currents. First, ...