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The signaling pathway in the postsynaptic CA1 pyramidal neuron causes long-term potentiation (LTP) of the slow inhibitory postsynaptic current (sIPSC) mediated by merabotropic GABA(sub B) receptors and G protein-activated inwardly rectifying K+ channels, both residing in dendritic spines as well as shafts. Significant differences were observed in the regulatory mechanisms for excitatory and inhibitory synaptic plasticity.

Five immobilizing materials were investigated for the catalytic efficiency of whole cells of Penicillium purpurogenum Li-3 (w-PGUS) and alginate gel was found the best polymer for the biotransformation of glycyrrhizin (GL) into glycyrrhetic acid 3-O-mono-β-d-glucuronide (GAMG). The activity of compositionally optimized w-PGUS alginate beads was examined in different ionic liquids (ILs). The 30% (v/v) hydrophilic IL [BMIM]BF4 in reaction mixture exhibited an explicit biocompatibility with alginate support; consequently aggrandized the catalytic efficiency of the immobilized w-PGUS compared with pure buffer and ILs media. The optimal biotransformation conditions of the immobilized w-PGUS were evaluated and compared with buffer and IL co-solvent media: including w-PGUS beads concentration (70g/l vs. 80g/l), substrate concentration (5mM vs. 4mM), temperature (45°C vs. 45°C), pH (5.4 vs. 5.6), and shaking speed (180rpm vs. 160rpm). Under the optimized conditions; the yield of GAMG was 2.62g/l after 62h in IL co-solvent medium compared to 2.34g/l after 72h in buffer medium. The immobilized w-PGUS also retained 45.80% and 18.13% of their original activity in IL co-solvent and buffer media respectively; after ten repeated batches displaying high operational stability for GL biotransformation. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus is a marine foodborne pathogenic bacterium commonly found in seawater or seafood. This bacterium often encounters low salinity stress when the contaminated seafood is washed with fresh water during food processing. This study was conducted to investigate the response of exponential- and stationary-phase cells of V. parahaemolyticus ST550 to lethal or sublethal low salinity. Tolerance to lethal low salinity (0.25% NaCl) was enhanced in V. parahaemolyticus cells in the exponential phase by previous adaptation in sublethal low salinity (0.6% NaCl). Low salinity-adapted cells in the exponential phase were also cross-protected against the challenge of lethal low pH, indifferent to heat, and sensitized to bile, acetic acid, and lactic acid stress. The adapted cells in the stationary phase were significantly protected against heat treatment at 44°C for 10 and 15 min, sensitized to bile and acetic acid treatment, and indifferent to low pH and lactic acid. [ABSTRACT FROM AUTHOR]

The majority of the BCR-ABL-negative myeloproliferative disorders express the mutant JAK2, JAK2V617F. Previously we showed that constitutive activation of this oncogenic JAK2 mutant in Ba/F3 or 32D cells requires coexpression of a cognate homodimeric cytokine receptor, such as the EpoR. However, overexpression of JAK2V617F in Ba/F3 cells renders them cytokine-independent for growth in the absence of an exogenous cytokine receptor. Here, we demonstrated that JAK2V617F domains required for receptor association are essential for cytokine-independent growth by overexpressed JAK2V617F, suggesting JAK2V617F is binding to an unknown endogenous cytokine receptor(s) for its activation. We further showed that disruption of EpoR dimerization by coexpressing a truncated EpoR disrupted JAK2V617F-mediated transformation, indicating that EpoR dimerization plays an essential role in the activation of JAK2V617F. Interestingly, coexpression of JAK2V617F with EpoR mutants that retain JAK2 binding but are defective in mediating Epo-dependent JAK2 activation due to mutations in a conserved juxtamembrane motif does lead to cytokine-independent activation of JAK2V617F. Overall, these findings confirm that JAK2V617F requires binding to a dimerized cytokine receptor for its activation, and that the key EpoR juxtamembrane regulatory motif essential for Epo-dependent JAK2 activation is not essential for the activation of JAK2V617F. The structure of the activated JAK2V617F is thus likely to be different from that of the activated wild-type JAK2, raising the possibility of developing a specifically targeted therapy for myeloproliferative disorders. [ABSTRACT FROM AUTHOR]

Abstract: Phorbol-12-myristate-13-acetate (PMA) induces megakaryocytopoeisis in human erythroleukemia (HEL) cells which is characterized by the increase in cell size, increase in nuclear polyploidization and expression of megakaryocyte marker, CD41. However, upon treatment with 100nM of selective prostacyclin (IP) agonist beraprost inhibits the induced differentiation. Moreover, selective non-prostanoid IP agonist, BMY 45778 prevents PMA induced megakaryocytopoeisis in HEL cells similarly, while prostaglandin E2 and specific EP3 agonist sulprostone have no effect. Thus, IP receptor is involved. Furthermore, adenylate cyclase activator forskolin and cAMP analog dibutyryl-cAMP also prevented PMA induced megakaryocytopoeisis in HEL cells. Thus, IP agonists inhibition of PMA induced megakaryocytopoeisis in HEL cells may involve a cAMP dependent pathway. [Copyright &y& Elsevier]

Carbonaceous matter (CM) is one of the main reasons for the decrease of gold recovery in refractory gold ores. Bio-pretreatment of carbonaceous gold ores makes the reduction the preg-robbing of gold, and has attracted significant attention recently due to its economic feasibility and environmental friendliness. In this study, the graphite was used as surrogate material to investigate the effect of Acidithiobacillus ferrooxidans (A. ferrooxidans) and Leptospirillum ferrooxidans (L. ferrooxidans) on the gold adsorption by graphite in thiourea system. The results showed that graphite had a significant inhibitory effect on the growth of A. ferrooxidans and L. ferrooxidans. After bio-oxidation, the lamellar structure of graphite surface was blurred, and there was the formation of jarosite. In addition, some oxygen-containing groups such as O–H, S O and Fe–O appeared on the surface, but the C C bond cleaved. The adsorption capacity of graphite to gold decreased from 35.8% to 16.6% (A. ferrooxidans) and 18.4% (L. ferrooxidans) respectively. It can be concluded that the bio-oxidation by A. ferrooxidans and L. ferrooxidans can passivate and erode graphite, and contribute to decrease preg-robbing of gold from thiourea leaching solution. • The reduction of preg-robbing of gold by bio-oxidizing graphite was investigated. • Graphite can inhibit the growth of A. ferrooxidans and L. ferrooxidans. • The effect of A. ferrooxidans and L. ferrooxidans for deactivating CM was testified. • Preg-robbing of gold from thiourea leaching solution was reduced by bio-oxidization. [ABSTRACT FROM AUTHOR]

Glycoside hydrolases (GHs) have attracted special attention in research aimed at modifying natural products by partial removal of sugar moieties to manipulate their solubility and efficacy. However, these modifications are challenging to control because the low substrate specificity of most GHs often generates undesired by-products. We previously identified a GH2- type fungal β-glucuronidase from Aspergillus oryzae (PGUS) exhibiting promiscuous substrate specificity in hydrolysis of triterpenoid saponins. Here, we present the PGUS structure, representing the first structure of a fungalβ-glucuronidase, and that of an inactive PGUS mutant in complex with the native substrate glycyrrhetic acid 3-O-mono-β-glucuronide (GAMG). PGUS displayed a homotetramer structure with each monomer comprising three distinct domains: a sugar-binding, an immunoglobulin-likeβ-sandwich, and aTIMbarrel domain. Two catalytic residues, Glu414 and Glu505, acted as acid/base and nucleophile, respectively. Structural and mutational analyses indicated that the GAMG glycan moiety is recognized by polar interactions with nine residues (Asp162, His332, Asp414, Tyr469, Tyr473, Asp505, Arg563, Asn567, and Lys569) and that the aglycone moiety is recognized by aromatic stacking and by a π interaction with the four aromatic residues Tyr469, Phe470, Trp472, and Tyr473. Finally, structure-guided mutagenesis to precisely manipulate PGUS substrate specificity in the biotransformation of glycyrrhizin into GAMG revealed that two amino acids, Ala365 and Arg563, are critical for substrate specificity. Moreover, we obtained several mutants with dramatically improved GAMG yield (>95%). Structural analysis suggested that modulating the interaction of β-glucuronidase simultaneously toward glycan and aglycone moieties is critical for tuning its substrate specificity toward triterpenoid saponins. [ABSTRACT FROM AUTHOR]

Ubiquitination is a common mechanism of down-regulation of mitogenic receptors. Here, we show that ubiquitination of the erythropoietin receptor (EpoR) at Lys256 is necessary and sufficient for efficient Epo-induced receptor internalization, whereas ubiquitination at Lys428 promotes trafficking of activated receptors to the lysosomes for degradation. Interestingly, EpoR that cannot be ubiquitinated has reduced mitogenic activities and ability to stimulate the STAT5, Ras/MAPK, and PI3K/AKT signaling pathways. We therefore propose that ubiquitination of the EpoR critically controls both receptor down-regulation and downstream signaling. [ABSTRACT FROM AUTHOR]

JAK2 (Janus kinase 2) is essential for cytokine receptor signaling, and several lines of evidence support a causal role of an activating JAK2 mutation in myeloproliferative disorders. JAK2 activity is autoinhibited by its pseudokinase domain in the basal state, and the inhibition is released by cytokine stimulation; how engagement of the cognate receptor triggers this release is unknown. From a functional screen for gain-of-function JAK2 mutations, we discovered 13 missense mutations, nine in the pseudokinase domain and four in the Src homology 2 (SH2)-pseudokinase domain linker. These mutations identified determinants for autoinhibition and inducible activation in JAK2. Two of the mutants, K539I and N622I, resulted in erythrocytosis in mice. Scanning mutagenesis of the SH2-pseudokinase domain linker indicated that its N-terminal part was essential for interaction of JAK2 with the Epo receptor, whereas certain mutations in the C-terminal region conferred constitutive activation. We further showed that substitutions for Glu543-Asp544 in this linker or Leu611, Arg683, or Phe694 in the hinge proximal region of the pseudokinase domain resulted in activated JAK2 mutants that could not be further stimulated by Epo. These results suggest that the SH2-pseudokinase domain linker acts as a switch that relays cytokine engagement to JAK2 activation by flexing the pseudokinase domain hinge. [ABSTRACT FROM AUTHOR]

Janus tyrosine kinase 2 (JAK2) is essential for signaling by the thrombopoietin (TpoR) and erythropoietin (EpoR) receptors. In the absence of JAK2 most EpoR molecules are retained in the endoplasmic reticulum in an Endo H-sensitive form. In contrast, we show that in the absence of JAK2 a large fraction of the TpoR is processed to the mature Endo H-resistant form and reaches the cell surface. By studying chimeras of the TpoR and EpoR we show that high surface expression of the TpoR is entirely conferred by the membrane-proximal region of the intracellular domain that includes the juxtamembrane, Box 1, and Box 2 regions. The TpoR intracellular domain shows similar effects on receptor endocytosis rate as that of the EpoR, but does stabilize the mature receptor isoform from degradation. Co-expression of JAK2 further stabilizes mature TpoR and thus further increases its surface expression. This JAK2 effect depends on the Box 1 region, the only JAK2 interacting site in the TpoR. By contrast, EpoR requires Box 1 as well as the flanking 20 residues on the C-terminal side for JAK2 interaction and JAK2-dependent surface expression. Our study suggests that whereas cell surface expression of type I cytokine receptors requires their cognate JAKs, the mechanisms governing receptor-JAK interactions differ among receptors interacting with the same JAK protein. [ABSTRACT FROM AUTHOR]