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S An

Publications and source records attributed to S An.

At least 73 records · Page 4Linked to original sources
PubMed1994

Demonstration of a double-stranded DNA-stimulated protein kinase (DNA-PK) inhibitory activity in human HL-60 leukemia cells.

A 41,000 protein, p41, was highly purified from human promyelocytic HL-60 cells by chromatography on GTP-agarose columns. The purified p41 inhibited phosphorylation of endogenous substrates present in partially purified DNA-PK from HL-60 or HeLa cells, as well as phosphorylation of recombinant protein tau mediated by the purified HeLa DNA-PK. The ability of p41 to inhibit DNA-PK was largely abolished by heating at 95 degrees C for 30 min.

Chromatography, Affinity↗
PubMed1994

Molecular cloning of sheep lung dipeptidase: a glycosyl phosphatidylinositol-anchored ectoenzyme that converts leukotriene D4 to leukotriene E4.

Sheep lung dipeptidase was released from a plasma membrane preparation by digestion with a phosphatidylinositol-specific phospholipase C. The dipeptidase was purified to homogeneity using affinity chromatography followed by high performance liquid chromatography. The NH2-terminal sequence was determined and employed to prepare a probe to clone the c-DNA of the enzyme. The primary structure of sheep lung dipeptidase, deduced from the c-DNA exhibited a high homology to kidney dipeptidases cloned from other animal species. Northern analysis detected the m-RNA of the dipeptidase in lung, kidney, and intestinal tissues of the sheep.

Amino Acid Sequence↗
PubMed1994

Effects of IFN-beta on growth of human prostatic JCA-1 cells.

Addition of IFN-beta resulted in a dose-dependent reduction of growth, a drop in [3H]thymidine incorporation into DNA, and a concurrent 69% and 15% increase in the S and G2/M phases, of the human prostatic JCA-1 cells. No correlation existed between the antimitogenicity of IFN and increases in the double-stranded RNA-dependent protein kinase activity. Although IFN elicited a large increase in 2-5A synthetase activity, activation of the 2-5A-dependent RNase L could not be demonstrated in JCA-1 cells rendered permeable to 2-5A, implying that the 2-5A pathway is not involved in the anti-proliferative effects of IFN. Analysis of endogenous proteins phosphorylated in vitro show that some IFN-inducible phosphoproteins were dependent upon the presence of double-stranded DNA.

2',5'-Oligoadenylate Synthetase↗
PubMed1994

Cloning and expression of the EP3-subtype of human receptors for prostaglandin E2.

Prostaglandin E2 (PGE2) is a potent mediator in many human tissues that is recognized by three distinct subtypes of receptors (Rs), designated EP1, EP2 and EP3. A cDNA from a human kidney library encodes a 367 amino acid protein, of 85% homology with the mouse EP3R, that is expressed predominantly in kidney tissue. Human EP3Rs of transfectants bound [3H]-PGE2 with a mean Kd of 2.6 nM and native specificity. In contrast to the reliance of EP2Rs on increases in the intracellular concentration of cyclic AMP ([cAMP]i) for cellular signaling, EP3Rs transduce both decreases in [cAMP]i and modest increases in [Ca++]i.

Amino Acid Sequence↗
PubMed1994

Inhibition of human HL-60 cell responses to chemotactic factors by antisense messenger RNA depletion of G proteins.

Chemotactic factors bound to receptors of the seven-transmembrane domain family signal leukocytes through associated guanine nucleotide-binding (G) proteins. Human leukocytes of the HL-60 line, which express G protein-coupled receptors for leukotriene B4 (LTB4) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) after differentiation with vitamin D3 and transforming growth factor-beta, were transfected with expression plasmids containing antisense-oriented cDNAs encoding the alpha-chains of Go, Gi1, Gi2, and Gi3. Antisense mRNA for Go and Gi2 alpha-chains suppressed by over 80% the level of the respective G protein. Go-deficient HL-60 cells had depressed functional and intracellular calcium responses to LTB4 and fMLP, but no alterations in the responses of cyclic adenosine 3',5'-monophosphate (cAMP). In contrast, HL-60 cells deficient in Gi2 lost only responses of the intracellular concentration of cAMP. Antisense mRNA suppression of distinct G proteins thus may delineate some transductional requirements for cellular responses.

Cell Line↗
PubMed1994

[Observations on gingival fibers of upper premolar region--structures and functions of dentogingival fibers].

It was the purpose of this paper to observe the structural features and discuss the functions of the dentogingival fibers in the human gingiva of the upper premolar region. They were observed by a light microscope. The results are as follows: 1. There is a large number of dentogingival fibers in the lingual gingiva of the upper premolar region. 2. Ten to fifteen dentogingival fibers form a bundle. And the bundle is twisted. 3. The dentogingival fibers increase in proportion to the thickening of the gingiva, and it seems that the dentogingival fibers is one of the main functional fibers. 4. Enlargement of the epithelial attachment and the increase of the fibers in the papillae accompany the cell differentiation of the epithelial basal cells. 5. It is observed that the tension of the dentogingival fibers extend widely to the epithelial cells of the stratum spinosum.

Bicuspid↗
PubMed1994

mRNA levels and methylation patterns of the 2-5A synthetase gene in control and Alzheimer's disease (AD) fibroblasts.

We have examined the mRNA levels and methylation patterns of the interferon-inducible 2',5'-oligoadenylate (2-5A) synthetase gene in skin fibroblasts derived from AD and age/sex-matched control subjects. Northern or slot hybridization analysis of total RNA showed a 63% and 46% decrease in the steady state level of 2-5A synthetase mRNA in AD cells as compared to controls, following a 24 h and 48 h treatment with IFN-beta ser. The 2-5A synthetase gene as studied by Southern analysis using the methylation-sensitive restriction enzymes HpaII and Msp I was found to be hypomethylated in AD cells. No difference in methylation patterns of the actin gene existed between control and AD fibroblasts.

2',5'-Oligoadenylate Synthetase↗
PubMed1994

Regulation of cell growth and the c-myc proto-oncogene expression by phorbol ester 12-0-tetradecanoyl phorbol-13-acetate (TPA) in the androgen-independent human prostatic JCA-1 cells.

The proliferation of the human prostatic cancer JCA-1 cells showed a complex response to different concentrations of TPA. Whereas cells exposed for 24 h had growth reduction which was proportional to the concentration of TPA added to the culture media, they showed resistance to low (0.016 and 0.16 nM) but not high (> or = 1.6 nM) doses of TPA after 72 h. Growth-inhibited, treated cells also displayed a distinct cell morphology compared with the controls. Since c-myc expression has previously been shown to be correlated with cellular proliferation, we determined changes in its steady-state level in control and treated cells by Northern analysis. Following a 24h, 48h, and 72h treatment, with 16 nM TPA, c-myc mRNA was suppressed by 91%, 83%, and 78%, respectively, in good agreement with the extent of growth reduction observed. At the low dose of TPA (0.16 nM), however, the c-myc mRNA expression remained inhibited by 85% even though cell growth was only reduced by 10-14%. No difference in the total amount of c-myc protein could be detected between control and treated cells by Western analysis.

Androgens↗
PubMed1994

Comparative study of 2',5'-oligoadenylate (2-5A) synthetase in control and Alzheimer's disease (AD) cells.

The properties of 2-5A synthetase, an interferon (IFN)-inducible enzyme that catalyzes the synthesis of a natural nucleic acid with 2',5'-phosphodiester linkage, were investigated using extracts prepared from fibroblasts derived from AD and age/sex-matched controls. Significant differences were found in kinetic parameters as well as activator requirements for the synthetase from the two sources. Fractionation of control and AD total lysates, the postribosomal supernatants, and the ribosomal salt washes, by gel filtration or by glycerol gradient centrifugation, also revealed a substantially different profile of elution of the enzyme. These results further support an altered 2-5A synthetase gene expression in AD cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1993

Cloning and expression of the EP2 subtype of human receptors for prostaglandin E2.

Prostaglandin E2 (PGE2) is a potent mediator in many human tissues, that is recognized by three distinct subtypes of receptors, designated EP1, EP2 and EP3. A cDNA from a human lung library encodes a 53 kDa protein of 88% homology with the mouse EP2 receptor. Human EP2 receptors in COS-7 cell transfectants bound [3H]-PGE2 with a mean Kd of 2.2 nM and native specificity, and transduced increases in the intra-cellular concentration of cyclic AMP, but not of Ca++. That most EP2 receptor mRNA is in lung, kidney, intestinal, glandular and immune tissues, is consistent with functional responses.

Amino Acid Sequence↗
PubMed1993

Variants of vasoactive intestinal peptide in mouse mast cells and rat basophilic leukemia cells.

Radioimmunoassays for neuroendocrine vasoactive intestinal peptide (VIP1-28) detected 30-120 fmol of structurally related peptides in extracts of 10(7) mouse peritoneal mast cells, bone marrow-derived mast cells, cultured PT-18 and C1.MC/C57.1 lines of mast cells, and rat basophilic leukemia (RBL) cells. No VIP was found in peritoneal cells of mast cell-deficient WBB6F1-W/Wv mice, whereas the amounts extracted from peritoneal cells of the congenic normal (WBB6F1-+/+) mice were similar to those from cultured mouse mast cells. Sephadex G-25 gel filtration resolved two different-sized variants of VIP from mouse mast cells and RBL cells. Amino acid sequence analyses showed that the smaller variant is VIP10-28. The principal amino-terminally larger variant of VIP from C1.MC/C57.1 mouse mast cells and RBL cells exhibited amino acid sequence homology with VIP(-6)-28, and this sequence was established for the corresponding larger VIP from PT-18 mast cells. Polymerase chain reaction amplification of two different substituent sequences of prepro VIP in RBL cell RNA identified the VIP message. VIP10-28 was released from mouse mast cells concurrently with histamine by IgE-dependent stimulation. Rodent mast cell-derived VIP thus consists of both the truncated VIP10-28 and amino-terminally larger forms that appear to be generated by peptidolysis of a preproVIP similar to that found in neural cells.

Amino Acid Sequence↗
PubMed1993

Phosphorylation of protein tau by double-stranded DNA-dependent protein kinase.

Alzheimer Disease (AD) is a distinct form of dementia characterized by the occurrence of neurofibrillary tangles, neurotic plaques and loss of certain neuronal populations. The tangles are associated with the presence of abnormal proteinaceous deposits. One such protein, referred to as tau, is found to be excessively phosphorylated in AD. We demonstrate that a double-stranded DNA-stimulated protein kinase (referred to as DNA-PK) effectively catalyzes the phosphorylation of recombinant human protein tau. Moreover, in the presence of stimulatory DNA, the hyperphosphorylation of tau is accompanied by a significant shift in its mobility on SDS polyacrylamide gels. These results suggest that DNA-PK may contribute to the pathogenesis of AD.

Animals↗
PubMed1993

Stimulation of phosphorylation of a nuclear protein (NP-34) in cultured Alzheimer's disease (AD) fibroblasts by interferon response element and other double-stranded oligonucleotides.

The interferon stimulated responsive elements (IRE), which correspond to nucleotide sequences between -103 and -85 (IRE18) and between -103 and -61 (IRE42), of the human 2',5'-oligoadenylate (2-5A) synthetase gene, were found to stimulate the phosphorylation of a number of proteins when added to nuclear extracts prepared from cultured AD fibroblasts; the most significant increase being a 34-kD protein, NP-34. Such an IRE-stimulated phosphorylation was less pronounced in normal fibroblast extracts. Other oligomers tested for IRE-like activity were found to be differentially effective. The relative activity of oligomers was correlated with their ability to be organized into an IRE42-like conformation. The IRE-dependent stimulation of the phosphorylation of nuclear proteins is most likely associated with the activation of a double-stranded DNA-dependent protein kinase (DNA-PK) since the IRE-stimulated phosphorylation of NP-34 was enhanced by the addition of purified HeLa DNA-PK, but reduced by a DNA-PK-specific monoclonal antibody.

2',5'-Oligoadenylate Synthetase↗
PubMed1993

The anti-proliferative effects of nicotinamide and 3-aminobenzamide on human smooth muscle cells in vitro.

The proliferation of cultured human arterial smooth muscle cells (HASMC) was suppressed by nicotinamide and its analogue, 3-aminobenzamide, in a concentration-dependent manner, based on cell count and [3H]thymidine incorporation into DNA. The addition of 10 and 15 mM nicotinamide, or 6 mM 3-aminobenzamide, to HASMC, for 96 h, resulted in a 19.3%, 44% and 41.5% reduction of cell growth and inhibition of DNA synthesis. Since c-myc protooncogene expression has previously been correlated with cell proliferation, the steady state level of its mRNA was determined in control and treated HSMC by Northern analysis, following a 1 h treatment with the respective chemicals. Whereas c-myc mRNA was suppressed by nicotinamide in proportion to its ability to reduce HASMC growth, down regulation of c-myc by 3-aminobenzamide was much less than the observed antiproliferative effect. These results suggest that the growth regulatory properties of nicotinamide and 3-aminobenzamide in HASMC are probably unrelated to their activity in controlling c-myc gene expression.

Aorta, Thoracic↗
PubMed1993

Studies of biochemical changes in cultured skin fibroblasts derived from sporadic and familial Alzheimer's disease individuals: qualitative and quantitative changes in double-stranded DNA-stimulated phosphorylation of endogenous nucleoproteins.

Endogenous proteins phosphorylated in vitro with nuclear extracts prepared from skin fibroblasts of familial and sporadic AD subjects and age/sex-matched controls show qualitative/quantitative changes which were dependent upon the addition of natural and synthetic double-stranded DNA (dsDNA) to assay mixtures. Control and AD cell-free homogenates showed a pronounced increase in four proteins migrating with molecular weights of 180- (p180), 75-(p75), 65- (p65), and 34-kD (p34). Optimal stimulation of each protein required a different concentration of dsDNA. In AD samples, an additional dsDNA-stimulated protein, p40, was observed. In extracts prepared from sporadic AD individuals, synthetic dsDNA stimulated the phosphorylation of two additional proteins, with molecular weights of 73- and 37-kD, which were not found in familial AD or control samples. These results suggest that dsDNA-stimulated phosphoprotein changes may be used to distinguish between familial and sporadic forms of AD.

Alzheimer Disease↗