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S Takasawa

Publications and source records attributed to S Takasawa.

At least 19 recordsLinked to original sources
PubMed1995

Nicotinamide inhibits IRF-1 mRNA induction and prevents IL-1 beta-induced nitric oxide synthase expression in pancreatic beta cells.

Nitric oxide produced by inducible nitric oxide synthase in islets exerts inhibitory and cytotoxic effects on pancreatic beta cells and is therefore thought to be a potent mediator in the pathogenesis of Type I diabetes mellitus. Here, using isolated rat pancreatic islets, we show that high-concentration nicotinamide (20 mM), but not low-concentration nicotinamide (5 mM), attenuates the interleukin-1 beta-evoked inhibition of glucose-induced insulin secretion by preventing the induction of interferon regulatory factor-1, a transcriptional factor which plays an essential role in inducible nitric oxide synthase gene expression, and the interleukin-1 beta-induced nitric oxide formation. High-concentration nicotinamide also restored an interleukin-1 beta-induced decrease in ATP content in pancreatic beta cells, suggesting that interleukin-1 beta-induced nitric oxide inhibits the mitochondrial function. The present results show the molecular basis of the preventive effect of high-dose nicotinamide on Type I diabetes mellitus.

Adenosine Triphosphate↗
PubMed1995

NAD(+)-glycohydrolase from Streptococcus pyogenes shows cyclic ADP-ribose forming activity.

NAD(+)-glycohydrolase from Streptococcus pyogenes was purified by successive chromatography on CM Sepharose CL-6B, Sephacryl S-200 HR and hydroxyapatite. The purified enzyme possessed synthesis and hydrolysis activities of cyclic ADP-ribose (cADPR), a newly found second messenger for Ca2+ mobilisation, along with cleavage activity of the ribose-nicotinamide bond in NAD+.

Adenosine Diphosphate Ribose↗
PubMed1995

The structure of the Aplysia kurodai gene encoding ADP-ribosyl cyclase, a second-messenger enzyme.

The complete nucleotide (nt) sequences of the cDNA and gene encoding the marine mollusk Aplysia kurodai (Ak) ADP-ribosyl cyclase (ADRC) which synthesizes cyclic ADP-ribose (cADP-ribose), a second messenger for Ca2+ mobilization from endoplasmic reticulum, were determined. Ak ADRC consists of 258 amino acids (aa) (29 kDa). It shares 86% aa sequence homology with that from A. californica, and 31-32% homology with the human, rat and mouse cluster of differentiation 38 (CD38) that has both ADRC and cADP-ribose hydrolase activities. The Ak ADRC-encoding gene (ADRC) spans approx. 7 kb and contains eight exons and seven introns. The transcription start point (tsp) determined by primer extension analysis and S1 mapping is 28 bp downstream from the TATA box. This gene is expressed specifically in the ovotestis, although the mammalian CD38-encoding gene is expressed in many kinds of tissues and cells. The 5'-flanking region contains several consensus sequences responsible for the germ-cell-specific expression of the mouse zona pellucida 3 (ZP3) and Drosophila melanogaster chorion genes. The existence of the consensus sequences located at nt -1649, -1161, -234 and -90 may account for the ovotestis-specific expression of the Ak ADRC gene.

ADP-ribosyl Cyclase↗
PubMed1995

Nicotinamide-adenine dinucleotide regulates muscarinic receptor-coupled K+ (M) channels in rodent NG108-15 cells.

1. The possible role of nicotinamide-adenine dinucleotide (NAD+) and cyclic adenosine diphosphate ribose (cADPR) as regulators of M-type K+ currents (IK(M)) has been studied in whole-cell patch-clamped NG108-15 mouse neuroblastoma x rat glioma cells that had been transformed to express m1 muscarinic acetylcholine receptors (mAChRs). 2. Pre-incubation of NG108-15 cells for 6-8 h with streptozotocin (2-5 mM) reduced NAD+ levels by 40-50%. Nicotinamide (2-5 mM) increased NAD+ levels and prevented depletion by streptozotocin. 3. Streptozotocin pretreatment reduced the inhibition of IK(M) produced by 100 microM acetylcholine (ACh) from 51.6 +/- 7.0 to 29.1 +/- 7.5%. This was prevented by simultaneous pre-incubation with 2 mM nicotinamide or by adding 2 mM NAD+ to the pipette solution. Neither procedure significantly affected the initial amplitude of IK(M). 4. Inclusion of 2 microM cADPR in the pipette solution induced a slow loss of IK(M) with a time constant of about 20 min. 5. It is concluded that mAChR-induced inhibition of IK(M) requires intracellular NAD+. This might be needed for the formation of cADPR as a regulator or messenger for IK(M) inhibition.

Adenosine Diphosphate Ribose↗
PubMed1995

Assignment of CD38, the gene encoding human leukocyte antigen CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase), to chromosome 4p15.

CD38 has been used as a phenotype marker of lymphocyte differentiation. Recently, we have demonstrated that cyclic ADP-ribose can be synthesized and hydrolyzed by CD38 and acts as a second messenger in insulin secretion from pancreatic beta-cells. We have mapped the CD38 gene to human chromosome 4p15 by fluorescence in situ hybridization.

ADP-ribosyl Cyclase↗
PubMed1994

ADP ribosyl cyclase activity of a novel bone marrow stromal cell surface molecule, BST-1.

Human BST-1, a bone marrow stromal cell surface molecule, is a GPI-anchored protein that facilitates the growth of pre-B cells. The deduced amino acid sequences of human and mouse BST-1 show around 30% homology with those of CD38 and Aplysia ADP ribosyl cyclase. Therefore, like CD38, BST-1 might possess ADP ribosyl cyclase activity. Here, we report the establishment of a stable transformant CHO cell line, which secretes truncated human soluble BST-1, and show that purified soluble BST-1 displays both ADP ribosyl cyclase and cADPR hydrolase activities.

ADP-ribosyl Cyclase↗
PubMed1994

Essential cysteine residues for cyclic ADP-ribose synthesis and hydrolysis by CD38.

We have recently demonstrated that cyclic ADP-ribose (cADPR) serves as a second messenger for glucose-induced insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373) and that human leukocyte antigen CD38 has both ADP-ribosyl cyclase and cADPR hydrolase activities (Takasawa, S., Tohgo, A., Noguchi, N., Koguma, T., Nata, K., Sugimoto, T., Yonekura, H., and Okamoto, H. (1993) J. Biol. Chem. 268, 26052-26054). Although the amino acid sequence of Aplysia ADP-ribosyl cyclase exhibits a high degree of amino acid sequence identity with that of CD38, the Aplysia enzyme shows only ADP-ribosyl cyclase but not cADPR hydrolase. In the present study, we introduced site-directed mutations to CD38 and found that C119K- and/or C201E-CD38 exhibited only ADP-ribosyl cyclase activity. Furthermore, Aplysia ADP-ribosyl cyclase into which we introduced the mutations K95C and E176C, which correspond to residues 119 and 201 of human CD38, exhibited not only ADP-ribosyl cyclase activity but also cADPR hydrolase. These results indicate that cysteine residues 119 and 201 in CD38 have crucial roles in the synthesis and hydrolysis of cADPR.

ADP-ribosyl Cyclase↗
PubMed1994

Characterization of the 5'-regulatory region of rat Reg I gene.

We report here the characterization of the 5'-regulatory region of rat Reg I gene encoding a growth stimulating factor for pancreatic beta-cells. Transient expression assays of the 5'-flanking region/luciferase fusion gene in AR4-2J cells showed that the -304/-237 region contained positive cis-acting elements. Gel shift assays using AR4-2J and rat pancreas nuclear extracts showed the formation of a specific complex with the -256/-237 oligonucleotide.

Animals↗
PubMed1994

Transgenic mice overexpressing human vasoactive intestinal peptide (VIP) gene in pancreatic beta cells. Evidence for improved glucose tolerance and enhanced insulin secretion by VIP and PHM-27 in vivo.

Vasoactive intestinal peptide (VIP), a 28-amino acid peptide hormone, plays many physiological roles in the peripheral and central nervous systems. It has been proposed that endogenous VIP released from VIP-containing nerves is involved in the regulation of the secretory function of the endocrine pancreas. To test this hypothesis in vivo, we produced transgenic mice carrying the human VIP/peptide histidine methionine 27 (PHM-27) gene under the control of insulin promoter. In immunohistochemical analyses of islets, all the islet beta cells of transgenic mice were intensely stained for both VIP and PHM-27, consistent with the fact that these two peptides are encoded in a single mRNA (Itoh, N., Obata, K., Yanaihara, N., and Okamoto, H. (1983) Nature 304, 547-549). VIP was efficiently secreted from isolated transgenic islets in vitro. The blood glucose assays in free-fed mice indicated that the transgene lowered the blood glucose levels of transgenic mice (128 +/- 4 mg/dl) by about 20% below control levels (155 +/- 6 mg/dl). In the glucose tolerance test, at 60 min after glucose administration, the transgenic blood glucose levels (129 +/- 12 mg/dl) were much lower than control levels (175 +/- 13 mg/dl). The transgenic serum insulin levels at 15 min after glucose administration were 2.5-3.0-fold higher than control levels. The transgene was also effective in ameliorating glucose intolerance of 70% depancreatized mice. These results indicate that VIP and PHM-27 produced from the transgenic beta cells efficiently enhance glucose-induced insulin secretion from beta cells by an autocrine mechanism. These results also suggest that genetic manipulation of islet beta cells by the human VIP/PHM-27 gene or delivery of VIP to beta cells may ultimately provide a valuable approach to enhancing insulin secretion in clinical diabetes.

Animals↗
PubMed1994

Structural determination and characterization of a 40 kDa protein isolated from rat 40 S ribosomal subunit.

We have purified a 40 kDa protein from the rat 40 S ribosomal subunit and determined its primary structure by amino acid and cDNA sequencing. The amino acid sequence of the 40 kDa protein shared 29-37% homology with prokaryotic ribosomal protein S2 of eubacteria and chloroplasts, indicating that the protein is a eukaryotic counterpart to prokaryotic S2. Moreover, the amino acid sequence shared 99% identity with those deduced from cDNAs for 68 kDa laminin binding proteins of human, murine and bovine origins. The cDNAs are capable of encoding polypeptides with predicted molecular mass of 33,000 which lacked typical signal sequences, N-linked glycosylation sites and putative transmembrane domains. These results indicate that the cDNAs for 68 kDa laminin binding proteins actually code for the 40 kDa ribosomal protein.

Amino Acid Sequence↗
PubMed1994

Cyclic ADP-ribose modulates Ca2+ release channels for activation by physiological Ca2+ entry in bullfrog sympathetic neurons.

Although Ca(2+)-induced Ca2+ release (CICR) via ryanodine receptors has been found to occur in intact neurons, little is known about the physiological processes that regulate it. We studied the effects of cyclic ADP-ribose (cADPR) on CICR in cultured bullfrog sympathetic neurons by fura-2 fluorescence recording and patch-clamp techniques. cADPR applied through a patch pipette augmented action potential- or depolarizing pulse-induced rises in intracellular Ca2+ without a change in Ca2+ entry initiating the responses, but not in the presence of ryanodine. Likewise, cADPR enhanced a single or oscillatory rise(s) in intracellular Ca2+ induced by caffeine. These results strongly suggest that cADPR can be an endogenous modulator of ryanodine receptors in neurons.

Adenosine Diphosphate Ribose↗
PubMed1993

Synthesis and hydrolysis of cyclic ADP-ribose by human leukocyte antigen CD38 and inhibition of the hydrolysis by ATP.

Cyclic ADP-ribose (cADPR) has been recently shown to be generated in pancreatic beta-cells by glucose stimulation, serving as a second messenger for Ca2+ mobilization in the endoplasmic reticulum in the process of insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). In the present study, we isolated a cDNA for CD38, which has been reported to be a human leukocyte antigen, from a human insulinoma and expressed the cDNA in COS-7 cells. CD38 expression was observed in the plasma membrane and the microsome fractions of the COS-7 cells. When we incubated the plasma membrane fraction with NAD+ and analyzed the reaction products by high pressure liquid chromatography, the formation of cADPR was observed in addition to the ADP-ribose (ADPR) formation. When the plasma membrane fraction was incubated with cADPR, cADPR was converted to ADPR stoichiometrically. These results suggest that CD38 has both cADPR-forming and -hydrolyzing activities. Moreover, we found that ATP (2-10 mM), generated in the glucose metabolism in beta-cells, inhibited the cADPR-hydrolyzing activity, resulting in the increased formation of cADPR. These findings indicate a role for CD38 in the synthesis and hydrolysis of cADPR in the process of insulin secretion in pancreatic beta-cells.

ADP-ribosyl Cyclase↗
PubMed1993

Cyclic ADP-ribose in insulin secretion from pancreatic beta cells.

Inositol 1,4,5-trisphosphate (IP3) is thought to be a second messenger for intracellular calcium mobilization. However, in a cell-free system of islet microsomes, cyclic adenosine diphosphate-ribose (cADP-ribose), a nicotinamide adenine dinucleotide (NAD+) metabolite, but not IP3, induced calcium release. In digitonin-permeabilized islets, cADP-ribose and calcium, but not IP3, induced insulin secretion. Islet microsomes released calcium when combined with the extract from intact islets that had been incubated with high concentrations of glucose. Sequential additions of cADP-ribose inhibited the calcium release response to extracts from islets treated with high concentrations of glucose. Conversely, repeated additions of the islet extract inhibited the calcium release response to a subsequent addition of cADP-ribose. These results suggest that cADP-ribose is a mediator of calcium release from islet microsomes and may be generated in islets by glucose stimulation, serving as a second messenger for calcium mobilization in the endoplasmic reticulum.

Adenosine Diphosphate Ribose↗
PubMed1992

The primary structure of rat rig/ribosomal protein S15 gene.

We have isolated rat rig/ribosomal protein S15 gene from a DNA library derived from a rat insulinoma and determined the complete nucleotide sequence. The rat rig/S15 gene is composed of four exons and three introns spanning 2 kbp and exhibits distinctive structural features unique for a ribosomal protein gene.

Amino Acid Sequence↗
PubMed1992

Structural determination of Saccharomyces cerevisiae rig gene and identification of its product as ribosomal protein S21.

rig was originally isolated from a rat insulinoma-derived cDNA library. The 145 amino acid sequence of the rig protein is invariant in mammalian cDNAs. In this paper, we have isolated the cDNA and genomic clones for yeast (Saccharomyces cerevisiae) rig, determined their nucleotide sequences, and identified the gene product. The gene and the mRNA encode a basic protein of 142 amino acids which has 61.3% amino acid identity with mammalian rig protein. On two-dimensional gel electrophoresis, the in vitro transcription/translation product of yeast rig cDNA co-migrated with yeast ribosomal protein S21. These results led to the conclusion that yeast rig ribosomal protein S21 and to the determination of the previously unknown primary structure of yeast S21 protein. Unlike most ribosomal protein genes of S. cerevisiae, the gene exists as a single copy in a haploid set of the yeast genome and has no intron, locating at chromosome VII or XV.

Amino Acid Sequence↗
PubMed1991

Sequence of the chicken rig gene encoding ribosomal protein S15.

The nucleotide sequence of the chicken rig gene encoding ribosomal protein S15 was determined. The 1.6-kb gene consists of four exons and three introns. The 5'-flanking region of the gene lacks TATA- or CAAT-box sequences. Several GC-box sequences were found around the transcription start point.

Amino Acid Sequence↗
PubMed1991

rig encodes ribosomal protein S15. The primary structure of mammalian ribosomal protein S15.

rig, a gene originally isolated from a rat insulinoma cDNA library, codes for a basic 145 amino acid protein [( 1986) Diabetes 35, 1178-1180]. Here we show that the immunoreactivity to a monoclonal antibody against the deduced rig protein and the translation product of rig mRNA comigrated with ribosomal protein S15. The amino acid sequence of ribosomal protein S15 purified from rat liver coincided with that deduced from the nucleotide sequence of rig mRNA, but there were indications that the initiator methionine was removed and the succeeding alanyl residue was monoacetylated. From these results, we conclude that the product of rig is ribosomal protein S15.

Amino Acid Sequence↗