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.     

Eutrophication of mountain lakes in Japan due to increasing deposition of anthropogenically produced dust

Atmospheric dust has wide-reaching effects, not only influencing climate conditions, but also ecosystems. The eastern region of the Asian continent is one of the largest emitters of dust in the world, and recent economic growth in the region has been accompanied by an increase in anthropogenic emissions. However, the effects of increased Asian dusts on aquatic ecosystems are not well understood. We examined fossil pigments and zooplankton remains from ²¹⁰Pb-dated sediments taken from high mountain lakes of Hourai-Numa and Hachiman-Numa, located in the Towada-Hachimantai National Park of Japan Islands, to uncover historical changes in the phyto- and zooplankton community over the past 100?years. Simultaneously, we measured the geochemical variables of TOC, TN, TP, ??¹³C, ??¹⁵N, and lead isotopes (²⁰⁷Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁶Pb) in the sediments to identify environmental factors causing such changes. As a result, despite few anthropogenic activities in the watersheds, alpine lakes in Japan had increased algal and herbivore plankton biomasses by 3?C6 fold for recent years depending on the surrounding terrestrial vegetation and landscape conditions. Biological and biogeochemical proxies recorded from the lake sediments showed that this eutrophication occurred after the 1990s when P deposition increased as a result of atmospheric loading of dust transported from the Asian continent. The continued increase of anthropogenically produced dust may therefore impart damaging impacts on mountain ecosystems even if they are protected from direct anthropogenic disturbances.     

A novel factor FLOURY ENDOSPERM2 is involved in regulation of rice grain size and starch quality

Rice (Oryza sativa) endosperm accumulates a massive amount of storage starch and storage proteins during seed development. However, little is known about the regulatory system involved in the production of storage substances. The rice flo2 mutation resulted in reduced grain size and starch quality. Map-based cloning identified FLOURY ENDOSPERM2 (FLO2), a member of a novel gene family conserved in plants, as the gene responsible for the rice flo2 mutation. FLO2 harbors a tetratricopeptide repeat motif, considered to mediate a protein-protein interactions. FLO2 was abundantly expressed in developing seeds coincident with production of storage starch and protein, as well as in leaves, while abundant expression of its homologs was observed only in leaves. The flo2 mutation decreased expression of genes involved in production of storage starch and storage proteins in the endosperm. Differences between cultivars in their responsiveness of FLO2 expression during high-temperature stress indicated that FLO2 may be involved in heat tolerance during seed development. Overexpression of FLO2 enlarged the size of grains significantly. These results suggest that FLO2 plays a pivotal regulatory role in rice grain size and starch quality by affecting storage substance accumulation in the endosperm.     

Evidence for Conservation of the Calcitonin Superfamily and Activity-regulating Mechanisms in the Basal Chordate Branchiostoma floridae: INSIGHTS INTO THE MOLECULAR AND FUNCTIONAL EVOLUTION IN CHORDATES*

The calcitonin (CT)/CT gene-related peptide (CGRP) family is conserved in vertebrates. The activities of this peptide family are regulated by a combination of two receptors, namely the calcitonin receptor (CTR) and the CTR-like receptor (CLR), and three receptor activity-modifying proteins (RAMPs). Furthermore, RAMPs act as escort proteins by translocating CLR to the cell membrane. Recently, CT/CGRP family peptides have been identified or inferred in several invertebrates. However, the molecular characteristics and relevant functions of the CTR/CLR and RAMPs in invertebrates remain unclear. In this study, we identified three CT/CGRP family peptides (Bf-CTFPs), one CTR/CLR-like receptor (Bf-CTFP-R), and three RAMP-like proteins (Bf-RAMP-LPs) in the basal chordate amphioxus (Branchiostoma floridae). The Bf-CTFPs were shown to possess an N-terminal circular region typical of the CT/CGRP family and a C-terminal Pro-NH₂. The Bf-CTFP genes were expressed in the central nervous system and in endocrine cells of the midgut, indicating that Bf-CTFPs serve as brain and/or gut peptides. Cell surface expression of the Bf-CTFP-R was enhanced by co-expression with each Bf-RAMP-LP. Furthermore, Bf-CTFPs activated Bf-CTFP-R·Bf-RAMP-LP complexes, resulting in cAMP accumulation. These results confirmed that Bf-RAMP-LPs, like vertebrate RAMPs, are prerequisites for the function and translocation of the Bf-CTFP-R. The relative potencies of the three peptides at each receptor were similar. Bf-CTFP2 was a potent ligand at all receptors in cAMP assays. Bf-RAMP-LP effects on ligand potency order were distinct to vertebrate CGRP/adrenomedullin/amylin receptors. To the best of our knowledge, this is the first molecular and functional characterization of an authentic invertebrate CT/CGRP family receptor and RAMPs.     

Determination of Abundance and Biovolume of Bacteria in Sediments by Dual Staining with 4′,6-Diamidino-2-Phenylindole and Acridine Orange: Relationship to Dispersion Treatment and Sediment Characteristics

We measured the abundance and biovolume of bacteria in intertidal sediments from Tokyo Bay, Japan, by using a dual-staining technique (4′,6-diamidino-2-phenylindole and acridine orange) and several dispersion techniques (ultrasonic cleaner, ultrasonic sonicator, and tissue homogenizer). Dual staining reduced serious background fluorescence, particularly when used for silt-, clay-, and detritus-rich sediments, and allowed us to distinguish bacteria from other objects during both counting and sizing. Within the studied samples, the number of bacterial cells ranged from 0.20 × 10⁹ to 3.54 × 10⁹ g of wet sediment⁻¹. With the cleaner and sonicator treatments, the bacterial numbers for all of the sites initially increased with dispersion time and then became constant. For the homogenizer treatments, the highest bacterial numbers were observed with the shortest (0.5- to 2-min) treatments, and the counts then declined steeply as the homogenization time increased, indicating that cell destruction occurred. The cleaner treatment had the possibility of insufficient dispersion of bacteria for fine-grain sediments. Within the studied samples, the bacterial biovolume ranged from 0.07 to 0.22 μm³. With the cleaner and sonicator treatments, the biovolume peaked during the shorter dispersion time. This pattern was caused not by cell destruction but by the incremental portion of dispersed small cells. We concluded that with the cleaner and sonicator treatments, the longer dispersion time reflected the real size spectrum and was preferable for accurate estimation of mean bacterial biovolumes.     

Hesr1 and Hesr3 are essential to generate undifferentiated quiescent satellite cells and to maintain satellite cell numbers

Satellite cells, which are skeletal muscle stem cells, divide to provide new myonuclei to growing muscle fibers during postnatal development, and then are maintained in an undifferentiated quiescent state in adult skeletal muscle. This state is considered to be essential for the maintenance of satellite cells, but their molecular regulation is unknown. We show that Hesr1 (Hey1) and Hesr3 (Heyl) (which are known Notch target genes) are expressed simultaneously in skeletal muscle only in satellite cells. In Hesr1 and Hesr3 single-knockout mice, no obvious abnormalities of satellite cells or muscle regenerative potentials are observed. However, the generation of undifferentiated quiescent satellite cells is impaired during postnatal development in Hesr1/3 double-knockout mice. As a result, myogenic (MyoD and myogenin) and proliferative (Ki67) proteins are expressed in adult satellite cells. Consistent with the in vivo results, Hesr1/3-null myoblasts generate very few Pax7(+) MyoD(-) undifferentiated cells in vitro. Furthermore, the satellite cell number gradually decreases in Hesr1/3 double-knockout mice even after it has stabilized in control mice, and an age-dependent regeneration defect is observed. In vivo results suggest that premature differentiation, but not cell death, is the reason for the reduced number of satellite cells in Hesr1/3 double-knockout mice. These results indicate that Hesr1 and Hesr3 are essential for the generation of adult satellite cells and for the maintenance of skeletal muscle homeostasis.     

Enzymatic synthesis of a novel glycolipid biosurfactant, mannosylerythritol lipid-D and its aqueous phase behavior

Mannosylerythritol lipids (MELs) produced by yeasts are one of the most promising glycolipid biosurfactants. In this study, we succeeded in the preparation of a novel MEL homolog having no acetyl groups, namely MEL-D. MEL-D was synthesized by lipase-catalyzed hydrolysis of acetyl groups from a known MEL, and identified as 4-O-[2′,3′-di-O-alka(e)noyl-β-d-mannopyranosyl]-(2R,3S)-erythritol. The obtained MEL-D showed a higher critical aggregation concentration (CAC = 1.2 × 10⁻⁵ M) and hydrophilicity compared to known MELs, retaining an excellent surface tension lowering activity (the surface tension at the CAC was 24.5 mN/m). In addition, we estimated the binary phase diagram of the MEL-D–water system based on a combination of visual inspection, polarized optical microscopy, and SAXS measurement. From these results, MEL-D was found to self-assemble into a lamellar (L_α) structure over all ranges of concentration. Meanwhile, the one-phase L_α region of MEL-D was extended wider than those of known MELs. MEL-D might keep more water between the polar layers in accordance with the extension of the interlayer spacing (d). These results suggest that the newly obtained MEL-D would facilitate the application of MELs in various fields as a lamellar-forming glycolipid with higher hydrate ability.     

The systematic substitutions around the conserved charged residues of the cytoplasmic loop of Na+-driven flagellar motor component PomA

PomA, a homolog of MotA in the H+-driven flagellar motor, is an essential component for torque generation in the Na+-driven flagellar motor. Previous studies suggested that two charged residues, R90 and E98, which are in the single cytoplasmic loop of MotA, are directly involved in this process. These residues are conserved in PomA of Vibrio alginolyticus as R88 and E96, respectively. To explore the role of these charged residues in the Na+-driven motor, we replaced them with other amino acids. However, unlike in the H+-driven motor, both of the single and the double PomA mutants were functional. Several other positively and negatively charged residues near R88 and E96, namely K89, E97 and E99, were neutralized. Motility was retained in a strain producing the R88A/K89A/E96Q/E97Q/E99Q (AAQQQ) PomA protein. The swimming speed of the AAQQQ strain was as fast as that of the wild-type PomA strain, but the direction of motor rotation was abnormally counterclockwise-biased. We could, however, isolate non-motile or poorly motile mutants when certain charged residues in PomA were reversed or neutralized. The charged residues at positions 88-99 of PomA may not be essential for torque generation in the Na+-driven motor and might play a role in motor function different from that of the equivalent residues of the H+-driven motor.