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Biomedical subjects

T Katada

Publications and source records attributed to T Katada.

At least 91 records · Page 5Linked to original sources
PubMed1995

Accumulation of cyclic ADP-ribose measured by a specific radioimmunoassay in differentiated human leukemic HL-60 cells with all-trans-retinoic acid.

Cyclic adenosine diphosphoribose (cADPR) is a novel candidate for the mediator of Ca2+ release from intracellular Ca2+ stores. The formation of this cyclic nucleotide is catalyzed by not only Aplysia ADP-ribosyl cyclase but also an ecto-form enzyme of NAD+ glycohydrolase (NADase), which was previously identified as all-trans-retinoic acid (RA)-inducible CD38 in human leukemic HL-60 cells. In the present study, we developed a radioimmunoassay specific for cADPR, by which more than 100 fmol of cADPR could be detected without any interference by other nucleotides. The possible involvement of CD38 in the formation of cellular cADPR was investigated with the radioimmunoassay method. A marked increase in cellular cADPR was accompanied by all-trans-RA-induced differentiation of HL-60 cells. Moreover, a high level of cellular cADPR was observed in other leukemic cell lines, in which CD38 mRNA was expressed. Thus, CD38, which was initially identified as an NADase, appeared to be responsible for the formation of cellular cADPR.

ADP-ribosyl Cyclase↗
PubMed1995

G beta gamma directly binds to the carboxyl terminus of the G protein-gated muscarinic K+ channel, GIRK1.

beta gamma Subunits of heterotrimeric GTP-binding proteins (G beta gamma) activate the inwardly rectifying muscarinic K+ channel, GIRK1. The significant role for the carboxyl (C) terminus of GIRK1 in this interaction has been suggested. However, it is still unknown whether G beta gamma directly interacts with GIRK1. To elucidate the molecular basis of G beta gamma-activation of GIRK1, we examined the binding properties of G beta gamma to the C terminus of GIRK1 cloned from mouse brain cDNA library (MB-GIRK1). The C terminus of MB-GIRK1 fused with glutathione S-transferase directly bound to purified G beta gamma. Incubation of the C terminus with Gi pretreated with GTP gamma S, but not with GDP, resulted in the binding of Gi beta gamma to the protein. Purified G alpha-GDP, but not G alpha-GTP gamma S, inhibited the binding of G beta gamma to the fusion protein. These results indicate that G beta gamma dissociated from G alpha may directly bind to the C terminus of GIRK1.

Amino Acid Sequence↗
PubMed1995

Stimulation of mouse DNA primase-catalyzed oligoribonucleotide synthesis by mouse DNA helicase B.

Many prokaryotic and viral DNA helicases involved in DNA replication stimulate their cognate DNA primase activity. To assess the stimulation of DNA primase activity by mammalian DNA helicases, we analyzed the synthesis of oligoribonucleotides by mouse DNA polymerase alpha-primase complex on single-stranded circular M13 DNA in the presence of mouse DNA helicase B. DNA helicase B was purified by sequential chromatography through eight columns. When the purified DNA helicase B was applied to a Mono Q column, the stimulatory activity for DNA primase-catalyzed oligoribonucleotide synthesis and DNA helicase and DNA-dependent ATPase activities of DNA helicase B were co-eluted from the column. The synthesis of oligoribonucleotides 5-10 nt in length was markedly stimulated by DNA helicase B. The synthesis of longer species of oligoribonucleotides, which were synthesized at a low level in the absence of DNA helicase B, was inhibited by DNA helicase B. The stimulatory effect of DNA helicase B was marked at low template concentrations and little or no effect was observed at high concentrations. The mouse single-stranded DNA binding protein, replication protein A (RP-A), inhibited the primase activity of the DNA polymerase alpha-primase complex and DNA helicase B partially reversed the inhibition caused by RP-A.

Adenosine Triphosphatases↗
PubMed1995

Potentiation of Gi-mediated phospholipase C activation by retinoic acid in HL-60 cells. Possible role of G gamma 2.

Differentiated HL-60 cells acquire responsiveness to fMet-Leu-Phe (fMLP), which activates phospholipase C and O2- generation in a pertussis toxin-sensitive manner. Addition of retinoic acid (RA) for the last 24 h during dimethyl sulfoxide (Me2SO)-induced differentiation enhanced fMLP-dependent signals and interaction between fMLP receptor and G(i). RA modifies both the function and subunit composition of G(i)2, the predominant G(i) of HL-60 membranes, as shown by comparing purified G(i)2 from membranes of Me2SO-treated cells (D-G(i)2) to G(i)2 from membranes of cells treated with both Me2SO and RA (DR-G(i)2). As compared to D-G(i)2, DR-G(i)2 induced more fMLP binding when added to membranes of pertussis toxin-treated HL-60 cells and, in the presence of GTP gamma S, stimulated beta gamma-sensitive phospholipase C in extracts of HL-60 cells to a much greater extent at a lower concentrations. Immunoblasts revealed that RA induced expression of the gamma 2 subunit, which was otherwise undetectable in G(i)2 purified from HL-60 cells or in HL-60 membranes. Possibly by inducing expression of gamma 2, RA alters two functions of the G(i) beta gamma subunit, modulation of fMLP receptor-G(i)2 coupling and activation of the effector, Phospholipase C.

Cell Differentiation↗
PubMed1995

A subtype of opioid kappa-receptor is coupled to inhibition of Gi1-mediated phospholipase C activity in the guinea pig cerebellum.

PLC activity was stimulated either by 1-100 microM of GTP or by 100-3,000 microM Ca2+ in lysed synaptosomal membranes of the guinea pig cerebellum. The kappa-opioid receptor agonist selectively inhibited the PLC activity stimulated by 100 microM GTP, but not by 100-3,000 microM Ca2+. Pretreatment of membranes with PTX abolished such a kappa-agonist-induced inhibition of PLC activity. The reconstitution of Gi1, but not of Go purified from porcine brains with PTX-treated membranes showed a complete recovery of the kappa-agonist-inhibition of PLC activity. These findings suggest that a novel subtype kappa-receptor mediates inhibition of PLC through inhibiting the intrinsic activity of PTX-substrate G-proteins.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1995

A periodic network of G protein beta gamma subunit coexisting with cytokeratin filament in starfish oocytes.

Heterotrimeric G proteins are membrane-bound and carry signals from activated receptors on plasma membranes to cytoplasmic effector enzymes and channels. In starfish oocytes, the beta gamma subunit of G protein mediates 1-methyladenine stimulation of oocyte maturation. In order to investigate the localization of beta gamma subunits in starfish oocytes during oocyte maturation, we raised a monoclonal antibody against the beta subunit. By immunofluorescence microscopy using the antibody, immature oocytes show a network of fibers in the cytoplasm. The staining of fibers is beaded with a periodicity of 0.7 microns. The same staining pattern is obtained by anti-gamma subunit antibody. In addition, the fibers are stained by anti-cytokeratin antibody. These results indicate that the G protein beta gamma subunit coexists with cytokeratin filaments in starfish oocytes. Stimulation of oocyte maturation by 1-methyladenine causes the beta gamma subunit to be disassembled.

Animals↗
PubMed1995

Significance of Thr182 in the nucleotide-exchange and GTP-hydrolysis reactions of the alpha subunit of GTP-binding protein Gi2.

The crystal structures of the GTP- and GDP-bound alpha subunits of heterotrimeric GTP-binding proteins were recently determined, and a conserved Thr residue in the G2 (linker 2) region of the alpha subunits, which corresponds to Thr182 in Gi2 alpha, was deduced to interact with the gamma-phosphate of GTP and Mg2+. To investigate biochemically the significance of the Thr residue, we produced a mutant Gi2 alpha, in which Thr182 was substituted for Ala (T182A), in Escherichia coli. The rate of guanosine 5'-(gamma-thio)tri-phosphate (GTP gamma S) binding to T182A was higher than that to the wild-type Gi2 alpha, especially with a high concentration (10 mM) of Mg2+. The rate of dissociation of bound GDP from T182A was also much faster than that from the wild-type with the high Mg2+ concentration. Moreover, T182A had much lower GTPase activity than the wild-type, like the gip mutant (R179C) of Gi2 alpha found in human endocrine tumors. The ability of T182A to interact with beta gamma subunits and membrane-bound receptors was the same as that of the wild-type alpha subunit. T182A could take on a GTP-bound active conformation, as judged from its sensitivity to tryptic digestion. These results indicated that Thr182 plays an important role not only in the Mg(2+)-sensitive GDP-GTP exchange reaction but also in the GTPase activity of Gi2 alpha. The T182A mutant of Gi2 alpha, characterized by the faster GDP release and the slower GTP hydrolysis, would be a novel mutant that retains the ability to interact with receptors and beta gamma subunits.

Alanine↗
PubMed1995

Enzyme properties of Aplysia ADP-ribosyl cyclase: comparison with NAD glycohydrolase of CD38 antigen.

An ecto-enzyme of NAD glycohydrolase (NADase) induced by retinoic acid in HL-60 cells is attributed to the molecule of CD38 antigen [Kontani, K., Nishina, H., Ohoka, Y., Takahashi, K., and Katada, T. (1993) J. Biol. Chem. 268, 16895-16898]. CD38 antigen has an amino acid sequence homologous to Aplysia ADP-ribosyl cyclase which generates cyclic adenosine diphosphoribose (cADPR) and nicotinamide (NA) from beta-NAD+. On the basis of this sequence homology, we compared enzyme properties between CD38 NADase expressed as a fusion protein in Escherichia coli and ADP-ribosyl cyclase purified from the ovotestis of Aplysia kurodai. 1) beta-NAD+ analogs, nicotinamide 1, N6-ethenoadenine dinucleotide, and nicotinamide hypoxanthine dinucleotide, did not serve as good substrates for the ADP-ribosyl cyclase, suggesting that the intact adenine ring of beta-NAD+ was required for the cyclase-catalyzed reaction. On the other hand, CD38 NADase utilized the NAD analogs to form ADP-ribose and NA. 2) Kinetic analyses of the ADP-ribosyl cyclase reaction revealed that NA was first released from the substrate (beta-NAD+)-enzyme complex, followed by the release of another product, cADPR, which was capable of interacting with the free enzyme. 3) The enzyme reaction catalyzed by the ADP-ribosyl cyclase was fully reversible; beta-NAD+ could be formed from cADPR and NA with a velocity similar to that observed in the degradation of beta-NAD+. However, CD38 NADase did not catalyze the reverse reaction to form beta-NAD+ from ADP-ribopase and NA. 4) The CD38 NADase activity was, but the ADP-ribosyl cyclase activity was not, inhibited by dithiothreitol.(ABSTRACT TRUNCATED AT 250 WORDS)

ADP-ribosyl Cyclase↗
PubMed1995

Involvement of pertussis toxin-sensitive mechanism in retinoic acid-induced differentiation of human leukemic HL-60 cells.

Retinoic acid-induced differentiation of human leukemic HL-60 cells is accompanied with the early induction of an ecto-enzyme of NAD+ glycohydrolase (NADase), which has recently been identified as human leukocyte cell surface antigen CD38 [Kontani, K. et al. (1993) J. Biol. Chem. 268, 16895-16898]. The terminal cell differentiation attendant upon the cell growth arrest was, but the early induction of CD38 NADase activity was not, inhibited by prior treatment of HL-60 cells with pertussis toxin, which catalyzed ADP-ribosylation of the membrane-bound alpha beta gamma-trimeric GTP-binding proteins. The prior treatment was, however, not essential for the toxin-induced inhibition of the cell differentiation; the inhibition by the addition of pertussis toxin was still observed even after retinoic acid-induced expression of CD38 antigen. This suggested that a pertussis toxin-sensitive mechanism was involved in a late process of cell differentiation. Indeed, HL-60 cells appeared to secrete a differentiation-supporting factor in response to retinoic acid, since the cell differentiation was accelerated and potentiated upon culture of the cells in a conditioned medium prepared from retinoic acid-treated cells. The action of the differentiation-supporting factor was destroyed by heating and markedly attenuated in pertussis toxin-pretreated HL-60 cells. Thus, the whole process of the retinoic acid-induced cell differentiation appeared to consist of two distinguishable periods in terms of sensitivity to pertussis toxin; the toxin-insensitive early period characterized by the induction of CD38 NADase activity and the toxin-sensitive late period in which the secretion of a differentiation-supporting factor might be involved.

ADP-ribosyl Cyclase↗
PubMed1995

Purification and characterization of the G203T mutant alpha i-2 subunit of GTP-binding protein expressed in baculovirus-infected Sf9 cells.

We expressed the Gly203-->Thr (G203T) mutant of Gi2alpha, which was expected to show a dominant-negative phenotype in Gi2-mediated signal transduction, in baculovirus-inefected Sf9 cells and purified the mutant alpha subunit for its characterization. The rate of dissociation of GDP from G203T Gi2alpha was 3- to 4-fold faster than that from wild type Gi2alpha, but their kappacat values for GTP hydrolysis were almost the same. The affinities of the two Gi2alpha proteins for the beta gamma subunits of G proteins to form alpha beta gamma timers, which served as substrates for pertussis toxin-catalyzed ADP-ribosylation, were the same. In marked contrast, G203T Gi2alpha was unable to form a tight complex with a non- hydrolyzable analog (GTP[gammaS) of GTP; bound GTP[gammaS] was readily released from the mutant Gi2alpha even in the presence of a high concentration of Mg2+. Its susceptibility to tryptic digestion also revealed that GTP[gammaS]-bound G203T Gi2alpha formed a conformation apparently different from that of the GTP[gammaS]-bound form of wild-type Gi2alpha. Both the G203T and wild-type Gi2alpha proteins were capable of coupling with membrane-bound alpha2-adrenergic receptors, resulting in the formation of receptor-G protein complexes with high affinity for agonists. However, GTP[gammaS]-dependent uncoupling from high-affinity receptors was markedly attenuated in the case of G203T Gi2alpha. Thus, G203T-mutated Gi2alpha had a unique property in terms of coupling to membrane receptors, in addition to the previously expected defect in the active conformation of the GTP-bound form of Gi2alpha.

Animals↗
PubMed1995

Mapping of G protein coupling sites of the angiotensin II type 1 receptor.

Angiotensin II type 1 (AT1) receptors have been identified in a wide variety of tissues, including the kidney, liver, adrenal gland, cardiovascular system, and brain. AT1 receptors also mediate complex signaling mechanisms that elicit a diversity of specific physiological effects. The rat AT1A receptor has seven transmembrane domains and couples with three distinct G proteins: Gq, Gi, and Go. But it is unknown which domains of AT1A couple with and activate each type of G protein. To identify the domains responsible for the activation of various types of G protein, we studied the effect of five different synthetic peptides representing different domains of cytosolic segments of the rat AT1A receptor on the binding of the 35S-labeled stable analogue of GTP, GTP gamma S. Peptides P-3, which is located in the N-terminal region of the putative third intracellular loop of AT1A (residues 216 through 230), and P-5 (residues 306 through 320), corresponding to the N-terminal region of the C-terminal tail, were found to activate purified Gi1, Gi2, and Go proteins. These results indicate that not only the third cytosolic loop but also the C-terminal cytosolic domain of AT1A is important for Gi1, Gi2, and Go protein coupling and activation.

Amino Acid Sequence↗
PubMed1995

Antiallergic constituents from oolong tea stem.

The antiallergic constituents of oolong tea stem were examined. The stem extracts inhibited the 48 h homologous passive cutaneous anaphylaxis (PCA) reactions or rats in a dose-dependent manner and showed the same extent of inhibitory activity as ketotifen. All antiallergic constituents from the stem were concentrated into chloroform and ethyl acetate fractions, when extracted by various solvents. These fractions were treated with polyvinylpolypyrrolidone (PVPP), which resulted in the elimination of antiallergic activity in the ethyl acetate fraction, suggesting that one of the antiallergic constituents may be tea catechins. Then, six kinds of catechins, (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), -epicatechin (EC), (+)-catechin (C) and (-)-gallocatechin gallate (GCG), were isolated from the ethyl acetate fraction, and the inhibitory activity of these catechins on histamine release from rat peritoneal mast cells passively sensitized with anti-egg albumin (EA) IgE antibody was investigated. Among these catechins, significant inhibitory activity was observed in all the catechins except for EC. In addition, the inhibitory activity of GCG was greater than that of EGCG, which is well known to be an antiallergic constituent in tea. These results suggest that GCG may be a novel antiallergic constituent among tea catechins, and also the most potent.

Animals↗
PubMed1994

Cell surface antigen CD38 identified as ecto-enzyme of NAD glycohydrolase has hyaluronate-binding activity.

An ecto-enzyme of NAD glycohydrolase induced by retinoic acid in human leukemic HL-60 cells is attributed to the molecule of leukocyte cell surface antigen CD38 (Kontani, K., et al. (1993) J. Biol. Chem. 268, 16895-16898). The cell surface antigen has an amino acid sequence homologous to Aplysia ADP-ribosyl cyclase that catalyzes the conversion of NAD to cyclic ADP-ribose with a calcium-mobilizing activity. A putative hyaluronate (HA)-binding motif which has recently been identified in CD44 antigen existed in the extracellular domain and intracellular amino terminus of CD38 antigen. CD38 antigen was indeed capable of binding to HA in a manner dependent on ionic strength. By contrast, no binding activity was found in Aplysia ADP-ribosyl cyclase. Thus CD38 antigen, like CD44 antigen characterized as a HA-receptor (or binding) protein, may function as an adhesion molecule.

ADP-ribosyl Cyclase↗
PubMed1994

Differential activation of adenylyl cyclase by protein kinase C isoenzymes.

Cyclic AMP production within cells is altered upon protein kinase C (PKC) activation; however, whether PKC directly modulates adenylyl cyclase (AC) catalytic activity has been controversial. Molecular studies have elucidated the existence of multiple PKC isoenzymes although the functional role of this diversity is not clear. Using purified PKC and AC isoenzymes, we demonstrate that PKC zeta directly phosphorylates type VAC, leading to an approximate 20-fold increase in its catalytic activity, a significantly larger enhancement than that achieved with forskolin (approximately 5-fold), the most potent activator of AC. When forskolin and PKC phosphorylation are combined, type V AC catalytic activity is increased 100-fold over basal levels. The two PKC isoenzymes (alpha and zeta) are additive in their capacity to activate AC, although PKC alpha is less potent than PKC zeta. Our data indicate that PKC can directly and potently regulate AC activity in an isoenzyme-specific manner, suggesting that direct cross-talk plays a major role in coordinating the activity of these two principal signal transduction pathways.

Adenylyl Cyclases↗
PubMed1994

An intrinsic guanine nucleotide exchange inhibitor in Gi2 alpha. Significance of G-protein self-suppression which antagonizes receptor signal.

The alpha subunit of Gi2 (Gi2 alpha) is a member of the heterotrimeric G protein family, which transduces receptor signals as a proto-oncogene product. We have found a novel self-suppressive region in Gi2 alpha near its C terminus. A polypeptide consisting of residues 338-352 of Gi2 alpha (Gi2 alpha-339-352) antagonizes receptor- and receptor peptide-stimulated Gi2 alpha activation, without affecting basal activity. Antagonism by Gi2 alpha-338-352 is attributable to an interaction with activated Gi2 alpha, which is not competitive with receptor polypeptides. Combined with the reports suggesting the presence of self-suppressive domains in a juxta-C-terminal portion of Gi2 alpha and G(o) alpha, this study supports the hypothesis that Gi2 alpha-338-352 constitutes an intrinsic guanine nucleotide exchange inhibitor, which in turn antagonizes receptor stimulation, suggesting that G proteins are activated by receptors through relaxation of a self-suppressive conformation.

Amino Acid Sequence↗
PubMed1994

Pertussis toxin-catalyzed ADP-ribosylation of GTP-binding proteins with digoxigenin-conjugated NAD. Identification of the proteins in plasma membranes and nuclei.

ADP-ribose moiety containing digoxigenin was transferred by pertussis toxin (IAP) to the alpha subunit of Gi (Gi alpha) from digoxigenin-conjugated NAD (DIG-NAD) in a beta gamma subunit-dependent manner. ADP-ribosylation of Gi alpha with DIG-NAD plus IAP was inhibited by native NAD. These results indicate that non-radiolabeled DIG-NAD also serves as the substrate for IAP-catalyzed ADP-ribosylation of G proteins. Using DIG-NAD and fluorescein isothiocyanate-labeled anti-digoxigenin antibody, IAP-sensitive G protein(s) was found to be exist in nuclei as well as plasma membranes of rat liver and HeLa cells. Thus, DIG-NAD is useful to identify pertussis toxin-substrate G proteins.

Adenosine Diphosphate Ribose↗
PubMed1994

Characterization of botulinum C3-catalyzed ADP-ribosylation of rho proteins and identification of mammalian C3-like ADP-ribosyltransferase.

The exoenzyme C3 produced by Clostridium botulinum catalyzes ADP-ribosylation of rho gene products which belong to a family of small molecular-weight GTP-binding proteins. The C3 enzyme-catalyzed ADP-ribosylation of rho proteins partially purified from bovine brain was markedly activated by certain types of detergents or phospholipids and by endogenous factors present in the brain cytosol. Rho A protein that had been expressed in E. coli and subsequential purified was readily ADP-ribosylated by the C3 enzyme even in the absence of the activating factors. These results suggest that partially purified rho proteins contain an inhibitor, probably rho GDI (GDP-dissociation inhibitor for rho p21), of C3-catalyzed ADP-ribosylation. The activity of an endogenous enzyme, having the same substrate as botulinum C3 enzyme, was also found in brain cytosol. The enzyme activity was partially purified and characterized. The enzyme appeared to have a molecular mass of approximately 20,000 on a gel filtration and displayed unique properties similar to those observed with the botulinum C3 enzyme. The alpha-subunits of alpha beta gamma-trimeric G proteins which served as the substrates of cholera or pertussis toxin were not ADP-ribosylated by the brain enzyme.

ADP Ribose Transferases↗