Eicosapentaenoic acid attenuates statin-induced ER stress and toxicity in myoblast

T cell activation requires both antigen specific and co-stimulatory signals that include the interaction of CD28 with its ligands CD80 and CD86. These signals are delivered by antigen presenting cells (APC) in the context of the immunological synapse (IS). Reorganization of the cytoskeleton is required for the formation and maintenance of the IS. Our results show that a highly conserved polylysine motif in CD86 cytoplasmic tail, herein referred to as the K4 motif, is responsible for the constitutive association of CD86 to the cytoskeleton in primary human APC as well as in a murine APC model. This motif is not involved in initial APC:T cell conjugate formation but mutation of the K4 motif affects CD86 reorientation at the IS. Importantly, APCs expressing CD86 with mutated K4 motif are severely compromised in their capacity to trigger complete T cell activation upon peptide presentation as measured by IL-2 secretion. Altogether, our results reveal the critical importance of the cytoskeleton-dependent CD86 polarization to the IS and more specifically the K4 motif for effective co-signaling.     

Environment of TyrZ in photosystem II from Thermosynechococcus elongatus in which PsbA2 is the D1 protein

The main cofactors that determine the photosystem II (PSII) oxygen evolution activity are borne by the D1 and D2 subunits. In the cyanobacterium Thermosynechococcus elongatus, there are three psbA genes coding for D1. Among the 344 residues constituting D1, there are 21 substitutions between PsbA1 and PsbA3, 31 between PsbA1 and PsbA2, and 27 between PsbA2 and PsbA3. Here, we present the first study of PsbA2-PSII. Using EPR and UV-visible time-resolved absorption spectroscopy, we show that: (i) the time-resolved EPR spectrum of Tyr_Z^• in the (S₃Tyr_Z^•)′ is slightly modified; (ii) the split EPR signal arising from Tyr_Z^• in the (S₂Tyr_Z^•)′ state induced by near-infrared illumination at 4.2 K of the S₃Tyr_Z state is significantly modified; and (iii) the slow phases of P₆₈₀^+⋅ reduction by Tyr_Z are slowed down from the hundreds of μs time range to the ms time range, whereas both the S₁Tyr_Z^• → S₂Tyr_Z and the S₃Tyr_Z^• → S₀Tyr_Z + O₂ transition kinetics remained similar to those in PsbA(1/3)-PSII. These results show that the geometry of the Tyr_Z phenol and its environment, likely the Tyr-O···H···Nϵ-His bonding, are modified in PsbA2-PSII when compared with PsbA(1/3)-PSII. They also point to the dynamics of the proton-coupled electron transfer processes associated with the oxidation of Tyr_Z being affected. From sequence comparison, we propose that the C144P and P173M substitutions in PsbA2-PSII versus PsbA(1/3)-PSII, respectively located upstream of the α-helix bearing Tyr_Z and between the two α-helices bearing Tyr_Z and its hydrogen-bonded partner, His-190, are responsible for these changes.     

Interaction between FliI ATPase and a flagellar chaperone FliT during bacterial flagellar protein export

FliT is a flagellar type III export chaperone specific for the filament-capping protein FliD. The FliT/FliD complex binds to the FliI ATPase of the flagellar export apparatus. The C-terminal α4 helix of FliT controls its interaction with FliI but it remains unknown how it does so. Here, we analysed the FliI-FliT interaction by pull-down assays using GST affinity chromatography. FliT94, missing the C-terminal α4 helix, bound to the extreme N-terminal region of FliI (FliI(EN)) with high affinity and to the C-terminal ATPase domain (FliI(CAT)) with low affinity. The C-terminal α4 helix of FliT suppressed the interaction with FliI(EN). FliH and FliT94 bound to a common binding site on FliI(EN) and hence FliH induced the release of FliI from FliT94 in an ATP-independent manner. FliD increased the binding affinity of FliI(CAT) for FliT. These results raise a possible hypothesis that the FliH/FliI complex binds to the FliT/FliD complex through FliI(CAT) to escort it from the cytoplasm to the export gate made up of six integral membrane proteins and that, upon dissociation of FliD from FliT, FliT94 may bind to FliI(EN) and then FliI may transfer from FliT94 to FliH by the direct competition of FliT94 and FliH for FliI(EN).     

Role of interaction of mannan-binding protein with meprins at the initial step of complement activation in ischemia/reperfusion injury to mouse kidney

Ischemia/reperfusion (I/R) is an important cause of acute renal failure. Recent studies have shown that the complement system mediated by the mannan-binding protein (MBP), which is a C-type serum lectin recognizing mannose, fucose and N-acetylglucosamine residues, plays a critical role in the pathogenesis of ischemic acute renal failure. MBP causes complement activation through the MBP lectin pathway and a resulting complement component, C3b, is accumulated on the brush borders of kidney proximal tubules in a renal I/R-operated mouse kidney. However, the initial step of the complement activation has not been studied extensively. We previously identified both meprins α and β, highly glycosylated zinc metalloproteases, localized on kidney proximal tubules as endogenous MBP ligands. In the present study, we demonstrated that serum-type MBP (S-MBP) and C3b were co-localized with meprins on both the cortex and the medulla in the renal I/R-operated mouse kidney. S-MBP was indicated to interact with meprins in vivo in the I/R-operated mouse kidney and was shown to initiate the complement activation through the interaction with meprins in vitro. Taken together, the present study strongly suggested that the binding of S-MBP to meprins triggers the complement activation through the lectin pathway and may cause the acute renal failure due to I/R on kidney transplantation and hemorrhagic shock.     

Abiotic stress-inducible receptor-like kinases negatively control ABA signaling in Arabidopsis

Membrane-anchored receptor-like protein kinases (RLKs) recognize extracellular signals at the cell surface and activate the downstream signaling pathway by phosphorylating specific target proteins. We analyzed a receptor-like cytosolic kinase (RLCK) gene, ARCK1, whose expression was induced by abiotic stress. ARCK1 belongs to the cysteine-rich repeat (CRR) RLK sub-family and encodes a cytosolic protein kinase. The arck1 mutant showed higher sensitivity than the wild-type to ABA and osmotic stress during the post-germinative growth phase. CRK36, an abiotic stress-inducible RLK belonging to the CRR RLK sub-family, was screened as a potential interacting factor with ARCK1 by co-expression analyses and a yeast two-hybrid system. CRK36 physically interacted with ARCK1 in plant cells, and the kinase domain of CRK36 phosphorylated ARCK1 in vitro. We generated CRK36 RNAi transgenic plants, and found that transgenic plants with suppressed CRK36 expression showed higher sensitivity than arck1-2 to ABA and osmotic stress during the post-germinative growth phase. Microarray analysis using CRK36 RNAi plants revealed that suppression of CRK36 up-regulates several ABA-responsive genes, such as LEA genes, oleosin, ABI4 and ABI5. These results suggest that CRK36 and ARCK1 form a complex and negatively control ABA and osmotic stress signal transduction.     

Radionuclide analysis on bamboos following the Fukushima nuclear accident

In response to contamination from the recent Fukushima nuclear accident, we conducted radionuclide analysis on bamboos sampled from six sites within a 25 to 980 km radius of the Fukushima Daiichi nuclear power plant. Maximum activity concentrations of radiocesium (134)Cs and (137)Cs in samples from Fukushima city, 65 km away from the Fukushima Daiichi plant, were in excess of 71 and 79 kBq/kg, dry weight (DW), respectively. In Kashiwa city, 195 km away from the Fukushima Daiichi, the sample concentrations were in excess of 3.4 and 4.3 kBq/kg DW, respectively. In Toyohashi city, 440 km away from the Fukushima Daiichi, the concentrations were below the measurable limits of up to 4.5 Bq/kg DW. In the radiocesium contaminated samples, the radiocesium activity was higher in mature and fallen leaves than in young leaves, branches and culms.     

Multiblock Copolymers with Highly Sulfonated Blocks Containing Di‐ and Tetrasulfonated Arylene Sulfone Segments for Proton Exchange Membrane Fuel Cell Applications

Multiblock copoly(arylene ether sulfone)s with different block lengths and ionic contents are tailored for durable and proton‐conducting electrolyte membranes. Two series of fully aromatic copolymers are prepared by coupling reactions between non‐sulfonated hydrophobic precursor blocks and highly sulfonated hydrophilic precursor blocks containing either fully disulfonated diarylsulfone or fully tetrasulfonated tetraaryldisulfone segments. The sulfonic acid groups are exclusively introduced in ortho positions to the sulfone bridges to impede desulfonation reactions and give the blocks ion exchange capacities (IECs) of 4.1 and 4.6 meq. g^?1, respectively. Solvent cast block copolymer membranes show well‐connected hydrophilic nanophase domains for proton transport and high decomposition temperatures above 310 °C under air. Despite higher IEC values, membranes containing tetrasulfonated tetraaryldisulfone segments display a markedly lower water uptake than the corresponding ones with disulfonated diarylsulfone segments when immersed in water at 100 °C, presumably because of the much higher chain stiffness and glass transition temperature of the former segments. The former membranes have proton conductivities in level of a perfluorosulfonic acid membrane (NRE212) under fully humidified conditions. A membrane with an IEC of 1.83 meq. g^?1 reaches above 6 mS cm^?1 under 30% relative humidity at 80 °C, to be compared with 10 mS cm^?1 for NRE212 under the same conditions.     

Design and synthesis of novel DFG-out RAF/vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors: 2. Synthesis and characterization of a novel imide-type prodrug for improving oral absorption

As an alternative to the previously reported solid dispersion formulation for enhancing the oral absorption of thiazolo[5,4-b]pyridine 1, we investigated novel N-acyl imide prodrugs of 1 as RAF/vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors. Introducing N-acyl promoieties at the benzanilide position gave chemically stable imides. N-tert-Butoxycarbonyl (Boc) introduced imide 6 was a promising prodrug, which was converted to the active compound 1 after its oral administration in mice. Cocrystals of 6 with AcOH (6b) possessed good physicochemical properties with moderate thermodynamic solubility (19μg/mL). This crystalline prodrug 6b was rapidly and enzymatically converted into 1 after its oral absorption in mice, rats, dogs, and monkeys. Prodrug 6b showed in vivo antitumor regressive efficacy (T/C=-6.4%) in an A375 melanoma xenograft model in rats. Hence, we selected 6b as a promising candidate and are performing further studies. Herein, we report the design, synthesis, and characterization of novel imide-type prodrugs.     

LOV domain-containing F-box proteins: light-dependent protein degradation modules in Arabidopsis

Plants constantly survey the surrounding environment using several sets of photoreceptors. They can sense changes in the quantity (=intensity) and quality (=wavelength) of light and use this information to adjust their physiological responses, growth, and developmental patterns. In addition to the classical photoreceptors, such as phytochromes, cryptochromes, and phototropins, ZEITLUPE (ZTL), FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1), and LOV KELCH PROTEIN 2 (LKP2) proteins have been recently identified as blue-light photoreceptors that are important for regulation of the circadian clock and photoperiodic flowering. The ZTL/FKF1/LKP2 protein family possesses a unique combination of domains: a blue-light-absorbing LOV (Light, Oxygen, or Voltage) domain along with domains involved in protein degradation. Here, we summarize recent advances in our understanding of the function of the Arabidopsis ZTL/FKF1/LKP2 proteins. We summarize the distinct photochemical properties of their LOV domains and discuss the molecular mechanisms by which the ZTL/FKF1/LKP2 proteins regulate the circadian clock and photoperiodic flowering by controlling blue-light-dependent protein degradation.     

CADLIVE optimizer: web-based parameter estimation for dynamic models

ABSTRACT: Computer simulation has been an important technique to capture the dynamics of biochemical networks. In most networks, however, few kinetic parameters have been measured in vivo because of experimental complexity. We develop a kinetic parameter estimation system, named the CADLIVE Optimizer, which comprises genetic algorithms-based solvers with a graphical user interface. This optimizer is integrated into the CADLIVE Dynamic Simulator to attain efficient simulation for dynamic models.