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101.
102.
Sinha D Bannergee S Schwartz JH Lieberthal W Levine JS 《The Journal of biological chemistry》2004,279(12):10962-10972
Mouse kidney proximal tubular epithelial (MK-PT) cells die by apoptosis over 7-10 days when deprived of all survival factors. We show here that withdrawal of all survival factors from MK-PT cells is associated with a progressive increase in the activity of extracellular signal-regulated kinase-1 and -2 (ERK1/2) and a progressive decrease in phosphorylated Akt, a kinase critical to cell survival. Pharmacological inhibition of MEK1/2, the immediate upstream kinase for ERK1/2, not only prevented the decrease in phosphorylated Akt, but also prolonged MK-PT cell survival. Inhibition of ERK1/2, by itself, in the absence of any other known survival factors, was as potent as epidermal growth factor in maintaining MK-PT cell viability. ERK1/2 co-immunoprecipitated with Akt in a multimolecular assembly of signaling molecules, containing at a minimum ERK1/2, Akt, Rsk, and 3-phosphoinositide dependent kinase 1 (PDK1). We hypothesize that the kinase Rsk, whose activation requires phosphorylation by both ERK1/2 and PDK1, acts as a bridge bringing ERK1/2 into proximity with PDK1-associated Akt. Although a number of interactions between the Raf-MEK-ERK and PI3K-Akt signaling pathways have been described, our results are the first to show modulation of Akt activity by signaling events originating with ERK1/2. Spontaneous activation of ERK1/2 occurs via MEK1/2 and appears to depend on oxidant stress, accompanying induction of the default pathway of apoptosis. Together, these data suggest that the spontaneous activation of ERK1/2, in the absence of known extracellular stimuli, represents a previously unrecognized major regulatory pathway determining the fate of cells destined to die by the default pathway of apoptosis. 相似文献
103.
104.
Earlier studies described the linkage of silver to antibodies using SH groups generated by the reduction of the SS groups
using ascorbic acid (1) analogous to the Thakur and DeFulvio technique for linking technetium to antibodies. This work describes
the linkage of silver to IgG after introducing SH groups by coupling the IgG to 2-imino thiolane. The protein was dissolved
in sodium acetate buffer pH 4.5 containing 1 mM EDTA by dialysis/gel chromatography in a concentration of 20 mg/mL. 2-Imino thiolane dissolved in Tris-HCl acetate buffer,
pH 8.2, 0.2M was added to give a final dilution of 0.2 mM 2-imino thiolane. The excess of 2-imino thiolane was removed by dialysis or G-25 Sephadex gel chromatography and then the
protein was reacted with silver nitrate 0.1 mM. The unreacted SH groups were blocked by adding iodoacetamide to a concentration of 5 mM. The nonprotein reagents again were removed by dialysis or gel chromatography. The thiol groups were titrated using 1.5 mM 2 2-Py-SS-Py prior to and after addition of silver. It was observed that depending on the concentration of silver, 50–80%
of the SH groups were coupled to silver. Higher concentrations of silver led to insoluble precipitates and should be avoided. 相似文献
105.
Pyridoxal 5'-phosphate (PLP) is an inhibitor of DNA polymerase activity of Escherichia coli DNA polymerase I large fragment. Kinetic studies indicated that overall PLP inhibition was noncompetitive with respect to dNTP, and Hill plot analysis revealed that two molecules of PLP were involved in the inhibition. Reduction of the PLP-treated enzyme with sodium [3H]borohydride resulted in covalent incorporation of 3 mol of PLP/mol of enzyme. This incorporation was at lysine residues exclusively, and the PLP-modified enzyme was not capable of DNA polymerase activity. The presence of dNTP during the modification reaction blocked the incorporation of 1 mol of PLP/mol of enzyme. Similar results were obtained in the presence or absence of template-primer. These data indicate that a PLP target lysine is in or around a dNTP binding site that is essential for polymerase activity and that this binding site is functional in the absence of template-primer. The enzyme modified in the presence of dNTP, containing 2 mol of PLP/mol of enzyme, was capable of DNA polymerase activity but was unable to conduct elongation of product molecules beyond a short oligonucleotide length. 相似文献
106.
107.
Laboratory and greenhouse experiments were conducted with two soilsviz., laterite and alluvial to study the transformation of applied Zn in soil fractions under submerged condition in the presence
and absence of added organic matter and its relationship with Zn nutrition of rice plants.
The results showed that application of organic matter caused a decrease in the concentration of Zn in shoot and root of rice
plants and helped in translocating the element from root to shoot. The per cent utilization of applied Zn by plants was also
found to increase by the application of organic matter. The transformation of applied Zn in different fractions in soils showed
that a major portion (53.6–72.6%) of it found its way to mineral fractions leaving only 1.0–3.3, 6.6–18.9, 11.0–21.6 and 2.3–8.8%
of the applied amounts in water soluble plus exchangeable, organic complexed, amorphous sesquioxides and crystalline sesquioxides
bound fractions respectively. Application of organic matter favoured such transformation of applied Zn into these fractions
except the mineral and crystalline sesquioxides bound ones.
Simple correlation and multiple regression analyses between applied Zn in different soil fractions and fertilizer Zn content
in plants showed that organic matter application increased the predictability of fertilizer Zn content in plants which has
been attributed to the higher per cent recovery of applied Zn in plant available fractions in soils in presence of added organic
matter. 相似文献
108.
Saswati?Banerjee Gopal?Chandra?MajumderEmail author 《Cellular & molecular biology letters》2010,15(2):356-364
Many studies have implicated cell-surface lectins in heterologous cell-cell adhesion, but little is known about the participation
of lectins in cellular adhesion in homologous cells. Here, we show the development of a cell model for investigating the direct
role of a cell-surface lectin in homologous cell-cell adhesion. Parenchymal cells were isolated from caprine liver using a
perfusion buffer, and dispersed in a chemically defined modified Ringer’s solution. These cells undergo autoagglutination
in the presence of Ca2+. The autoagglutinated cells can be dissociated specifically with D-galactose (50 mM), which also inhibits the liver cell
autoagglutination event. The blood serum protein fetuin has no effect on liver cell autoagglutination, whereas desialylated
fetuin (100 μM), with its terminal D-galactose residue, showed a high affinity for blocking the autoagglutination event. The
data demonstrates the occurrence of a Ca2+-dependent D-galactose-specific lectin and a lectin receptor on the parenchymal cells. Furthermore, it shows that the observed
autoagglutination event is caused by the interaction of the cell-surface lectin with its receptor on the neighbouring homologous
cells. The data supports the view that homologous cell-cell contact in mammalian tissues is triggered by such lectin-receptor
interaction and that the previously reported cell-surface adhesive proteins serve as a secondary force to strengthen cell
adhesion. This cell model could be extremely useful for investigating the direct role of cell-surface lectin and its receptor
in homologous cell adhesion in a variety of tissues under normal and pathological conditions. 相似文献
109.
Das A Wiederhold L Leppard JB Kedar P Prasad R Wang H Boldogh I Karimi-Busheri F Weinfeld M Tomkinson AE Wilson SH Mitra S Hazra TK 《DNA Repair》2006,5(12):1439-1448
DNA glycosylases/AP lyases initiate repair of oxidized bases in the genomes of all organisms by excising these lesions and then cleaving the DNA strand at the resulting abasic (AP) sites and generate 3' phospho alpha,beta-unsaturated aldehyde (3' PUA) or 3' phosphate (3' P) terminus. In Escherichia coli, the AP-endonucleases (APEs) hydrolyze both 3' blocking groups (3' PUA and 3' P) to generate the 3'-OH termini needed for repair synthesis. In mammalian cells, the previously characterized DNA glycosylases, NTH1 and OGG1, produce 3' PUA, which is removed by the only AP-endonuclease, APE1. However, APE1 is barely active in removing 3' phosphate generated by the recently discovered mammalian DNA glycosylases NEIL1 and NEIL2. We showed earlier that the 3' phosphate generated by NEIL1 is efficiently removed by polynucleotide kinase (PNK) and not APE1. Here we show that the NEIL2-initiated repair of 5-hydroxyuracil (5-OHU) similarly requires PNK. We have also observed stable interaction between NEIL2 and other BER proteins DNA polymerase beta (Pol beta), DNA ligase IIIalpha (Lig IIIalpha) and XRCC1. In spite of their limited sequence homology, NEIL1 and NEIL2 interact with the same domains of Pol beta and Lig IIIalpha. Surprisingly, while the catalytically dispensable C-terminal region of NEIL1 is the common interacting domain, the essential N-terminal segment of NEIL2 is involved in analogous interaction. The BER proteins including NEIL2, PNK, Pol beta, Lig IIIalpha and XRCC1 (but not APE1) could be isolated as a complex from human cells, competent for repair of 5-OHU in plasmid DNA. 相似文献
110.
This work evaluated the effect of bioremediation treatments including natural attenuation, bioaugmentation, biostimulation as well as combined biostimulation and bioaugmentation on degradation of 4-nitrotoluene (4-NT), 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) in soil microcosms. Bioaugmentation with a previously isolated NTs-degrading bacterium, Rhodococcus pyridinivorans NT2, showed an 86–88% decrease in 4-NT, 2,4-DNT or 2,6-DNT after 60 days. Irrespective of the substrate types, least degradation (6–6.5%) was observed in abiotic control. The addition of β-cyclodextrin or rhamnolipid significantly improved NTs degradation efficiency in soil (18.5–74%) than natural attenuation (22–25%). Exogenous addition of preselected bacterial isolate NT2 along with β-cyclodextrin/rhamnolipid resulted in the greatest number (1.8× and 2.5× high) of total heterotrophic aerobic bacteria and NT degraders, respectively, compared to natural attenuation. Irrespective of the treatment types, the population of NT degraders increased steadily in the first 5 weeks of incubation followed by a plateau within the next few weeks. The treatment BABS2 (Soil + rhamnolipid + NT2) yielded highest microbial-C and -N and dehydrogenase activity, consistent with results of NTs degradation and microbial counts in combined bioaugmentation and biostimulation. Thus the results of this study suggest that bioaugmentation by R. pyridinivorans NT2 may be a promising bioremediation strategy for nitroaromatics-contaminated soils. 相似文献