Adaptor protein Shc is an isoform-specific direct activator of the tyrosine kinase c-Src

The activity of c-Src protein-tyrosine kinase is up-regulated under a number of receptor signaling pathways. However, the activation mechanism of c-Src under physiological conditions has remained unclear. We show here that the Shc adaptor protein is a novel direct activator of c-Src in epidermal growth factor receptor signaling in A431 human epidermoid carcinoma cells. Among the three Shc isoforms, P66 and P52, but not P46, were found to interact with and activate c-Src in vitro and in vivo. Activation of c-Src accompanied autophosphorylation of c-Src in the activation segment, but the carboxyl-terminal dephosphorylation was not observed. We have identified the interaction sites between Shc and c-Src and constructed a point mutant of Shc that abolishes the c-Src activation. Using this mutant, we have confirmed that the Shc-mediated c-Src activation triggers Stat-p21/WAF1/Cip1 pathway that has been implicated in the cell cycle arrest and apoptosis of epidermal growth factor-stimulated A431 cells.     

Yersinia pseudotuberculosis infection in breeding monkeys: detection and analysis of strain diversity by PCR

In the last three decades, several monkeys reared in outdoor/indoor-outdoor breeding colonies and cages of the Primate Research Institute, Kyoto University, died of yersiniosis caused by Yersinia pseudotuberculosis, necessitating introduction of a method to detect the bacteria rapidly and thus allow preventive measures to be undertaken. A rapid nested polymerase chain reaction (PCR) method for identification of Y. pseudotuberculosis in fecal samples and a random amplified polymorphic DNA (RAPD)-PCR approach for distinguishing between bacterial strains were therefore developed. Yersinia pseudotuberculosis isolates from monkey specimens were found to be classifiable into several types. To determine the source of infection, hundreds of fecal samples of wild rats, pigeons, and sparrows were collected from around the breeding colonies and cages, and subjected to PCR analyses. Yersinia pseudotuberculosis was detected in 1.7% of the fecal samples of wild rats. The DNA fingerprints of the bacteria revealed by RAPD-PCR were the same as that of one strain isolated from macaques, suggesting the wild rat to be a possible source of infection.     

NADPH oxidase is involved in prostaglandin F2alpha-induced hypertrophy of vascular smooth muscle cells: induction of NOX1 by PGF2alpha

Prostaglandin (PG) F(2alpha), one of the primary prostanoids generated in vascular tissue, is known to cause hypertrophy in vascular smooth muscle cells. To clarify the molecular mechanisms underlying PGF(2alpha)-induced hypertrophy, the involvement of reactive oxygen species was examined in a rat vascular smooth muscle cell line, A7r5. PGF(2alpha) and (+)-fluprostenol, a selective agonist of the PGF receptor, significantly increased intracellular O(2)(-) in A7r5. The PGF(2alpha)-induced O(2)(-) increase was suppressed by diphenyleneiodonium (DPI), an inhibitor of NADPH oxidase that has been reported to be the major source of O(2)(-) in vascular cells. The augmented synthesis of the protein induced by PGF(2alpha) or (+)-fluprostenol was suppressed in the presence of DPI. In PGF(2alpha) or (+)-fluprostenol-treated cells, a dose-dependent increase in the expression of NOX1, a homolog of the catalytic subunit of the phagocyte NADPH oxidase gp91(phox), was demonstrated by Northern blot analysis. Finally, depletion of NOX1 mRNA in the cells transfected with ribozymes targeted for three independent cleavage sites on the mRNA sequence significantly reduced the PGF(2alpha)-induced increase in protein synthesis. Taken together, these results suggest that hypertrophy of vascular smooth muscle cells caused by PGF(2alpha) is mediated by NOX1 induction and the resultant overproduction of O(2)(-) by NADPH oxidase.     

Structure and electrochemistry of the bridging-ligand mono-substituted diruthenium compound, [Ru2(II,III)(O2CCH3)3(admpym)(Cl)(MeOH)] (Hadmpym=2-amino-4,6-dimethylpyrimidine)

The ligand substitution reaction of Ru₂(O₂CCH₃)₄Cl with 2-amino-4,6-dimethylpyrimidine (Hadmpym) under gentle refluxing conditions in methanol led to the formation of a bridging-ligand mono-substituted compound, [Ru₂(O₂CCH₃)₃(admpym)(Cl)(MeOH)] (1). Compound 1 crystallized in monoclinic space group P2₁/n (no. 14) with a=8.3074(8) Å, b=12.3722(8) Å, c=18.913(1) Å, β=95.559(3)°, V=1934.8(3) ų, and Z=4. Temperature dependence of the magnetic susceptibility of 1 revealed it to be in a spin ground state S=3/2 arising from the electronic configuration of σ²π⁴δ²(δ*π*)³. Compound 1 undergoes three metal-centered redox reactions in electrochemistry: E_1/2 ^(ox)=+0.72 V (I_a/I_c<1, ΔE_p=0.17 V); E_1/2 ^(1,red)=−0.65 V (I_a/I_c≈1, ΔE_p=0.10 V); and E_1/2 ^(2,red)=−1.80 V (I_a/I_c?1, ΔE_p=0.16 V). Then, the redox species produced by electrolysis were characterized by spectroscopic studies.     

High-level expression and characterization of fully active recombinant conger eel galectins in Eschericia coli

An expression system for recombinant conger eel galectins, congerins I and II, were constructed using the pTV 118N plasmid vector and Escherichia coli. Recombinant congerins I and II could be obtained in the soluble active form with high quantitative yield. Mutation of codons for Val and Leu located in the N-terminal region of Con I increased the expression efficiency. Purification of recombinant proteins were done by only two chromatographical steps from E. coli extract. The purified recombinant congerins were found to be almost the same as the native ones except for the acetyl group at the N-terminus; that is, they showed the same structures and carbohydrate binding activities, suggesting that N-terminal acetyl groups of congerins were not significant for activity.     

Bcl-2 prevents hypoxia/reoxygenation-induced cell death through suppressed generation of reactive oxygen species and upregulation of Bcl-2 proteins

The function of bcl-2 in preventing cell death is well known, but the mechanisms whereby bcl-2 functions are not well characterized. One mechanism whereby bcl-2 is thought to function is by alleviating the effects of oxidative stress upon the cell. To examine whether Bcl-2 can protect cells against oxidative injury resulting from post-hypoxic reoxygenation (H/R), we subjected rat fibroblasts Rat-1 and their bcl-2 transfectants b5 to hypoxia (5% CO2, 95% N2) followed by reoxygenation (5% CO2, 95% air). The bcl-2 transfectants exhibited the cell viability superior to that of their parent non-transfectants upon treatment with reoxygenation after 24-, 48-, or 72-h hypoxia, but not upon normoxic serum-deprivation or upon serum-supplied hypoxic treatment alone. Thus bcl-2 transfection can prevent cell death of some types, which occurred during H/R but yet not appreciably until termination of hypoxia. The time-sequential events of H/R-induced cell death were shown to be executed via (1) reactive oxygen species (ROS) production at 1-12 h after H/R, (2) activation of caspases-1 and -3, at 1-3 h and 3-6 h after H/R, respectively, and (3) loss of mitochondrial membrane potential (DeltaPsi) at 3-12 h after H/R. These cell death-associated events were prevented entirely except caspase-1 activation by bcl-2 transfection, and were preceded by Bcl-2 upregulation which was executed as early as at 0-1 h after H/R for the bcl-2 transfectants but not their non-transfected counterpart cells. Thus upregulation of Bcl-2 proteins may play a role in prevention of H/R-induced diminishment of cell viability, but may be executed not yet during hypoxia itself and be actually operated as promptly as ready to go immediately after beginning of H/R, resulting in cytoprotection through blockage of either ROS generation, caspase-3 activation, or DeltaPsi decline.     

Phenylpropanoid amides of serotonin accumulate in witches' broom diseased bamboo

Aciculosporium take (Ascomycota; Clavicipitaceae), causes the witches' broom disease in bamboo, particularly Phyllostachys bambusoides. Since it was observed that endogenous indole-3-acetic acid is reduced in the twigs of the diseased bamboo, the symptoms (bushy appearance) may be induced by reduction in auxin levels. Furthermore, two indolic compounds accumulated in diseased twigs, these being identified as N-p-coumaroylserotonin and N-feruloylserotonin by LC-MS, 1H NMR and 13C NMR spectroscopic analyses. N-p-Coumaroylserotonin possesses antifungal activity against A. take.     

Rapid increase of vacuolar volume in response to salt stress

Suspension-cultured cells of mangrove [Bruguiera sexangula (Lour.) Poir.] showed a rapid increase in vacuolar volume under salt stress, although there was no change in the cell volume. The rapid increase in the vacuolar volume was an active process, which followed the activation of the tonoplast H(+)-ATPase and the vacuolar acid phosphatase. The same phenomenon was observed in barley (Hordeum vulgare L. cv. Doriru) root meristematic cells under salt stress but not in pea ( Pisum sativum L.). Increases in vacuolar volume could potentially protect the cytoplasm by decreasing the cytoplasmic volume during the initial phases of salt stress.