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T Katada

Publications and source records attributed to T Katada.

At least 19 recordsLinked to original sources
PubMed2001

Association of FcgammaRII with low-density detergent-resistant membranes is important for cross-linking-dependent initiation of the tyrosine phosphorylation pathway and superoxide generation.

IgG immune complexes trigger humoral immune responses by cross-linking of FcRs for IgG (FcgammaRs). In the present study, we investigated role of lipid rafts, glycolipid- and cholesterol-rich membrane microdomains, in the FcgammaR-mediated responses. In retinoic acid-differentiated HL-60 cells, cross-linking of FcgammaRs resulted in a marked increase in the tyrosine phosphorylation of FcgammaRIIa, p58(lyn), and p120(c-cbl), which was inhibited by a specific inhibitor of Src family protein tyrosine kinases. After cross-linking, FcgammaRs and tyrosine-phosphorylated proteins including p120(c-cbl) were found in the low-density detergent-resistant membrane (DRM) fractions isolated by sucrose-density gradient ultracentrifugation. The association of FcgammaRs as well as p120(c-cbl) with DRMs did not depend on the tyrosine phosphorylation. When endogenous cholesterol was reduced with methyl-beta-cyclodextrin, the cross-linking did not induce the association of FcgammaRs as well as p120(c-cbl) with DRMs. In addition, although the physical association between FcgammaRIIa and p58(lyn) was not impaired, the cross-linking did not induce the tyrosine phosphorylation. In human neutrophils, superoxide generation induced by opsonized zymosan or chemoattractant fMLP was not affected or increased, respectively, after the methyl-beta-cyclodextrin treatment, but the superoxide generation induced by the insoluble immune complex via FcgammaRII was markedly reduced. Accordingly, we conclude that the cross-linking-dependent association of FcgammaRII to lipid rafts is important for the activation of FcgammaRII-associated Src family protein tyrosine kinases to initiate the tyrosine phosphorylation cascade leading to superoxide generation.

Cells, Cultured↗
PubMed2001

The stress kinase mitogen-activated protein kinase kinase (MKK)7 is a negative regulator of antigen receptor and growth factor receptor-induced proliferation in hematopoietic cells.

The dual specificity kinases mitogen-activated protein kinase (MAPK) kinase (MKK)7 and MKK4 are the only molecules known to directly activate the stress kinases stress-activated protein kinases (SAPKs)/c-Jun N-terminal kinases (JNKs) in response to environmental or mitogenic stimuli. To examine the physiological role of MKK7 in hematopoietic cells, we used a gene targeting strategy to mutate MKK7 in murine T and B cells and non-lymphoid mast cells. Loss of MKK7 in thymocytes and mature B cells results in hyperproliferation in response to growth factor and antigen receptor stimulation and increased thymic cellularity. Mutation of mkk7 in mast cells resulted in hyperproliferation in response to the cytokines interleukin (IL)-3 and stem cell factor (SCF). SAPK/JNK activation was completely abolished in the absence of MKK7, even though expression of MKK4 was strongly upregulated in mkk7(-/-) mast cell lines, and phosphorylation of MKK4 occurred normally in response to multiple stress stimuli. Loss of MKK7 did not affect activation of extracellular signal-regulated kinase (ERK)1/2 or p38 MAPK. mkk7(-/-) mast cells display reduced expression of JunB and the cell cycle inhibitor p16INK4a and upregulation of cyclinD1. Reexpression of p16INK4a in mkk7(-/-) mast cells abrogates the hyperproliferative response. Apoptotic responses to a variety of stimuli were not affected. Thus, MKK7 is an essential and specific regulator of stress-induced SAPK/JNK activation in mast cells and MKK7 negatively regulates growth factor and antigen receptor-driven proliferation in hematopoietic cells. These results indicate that the MKK7-regulated stress signaling pathway can function as negative regulator of cell growth in multiple hematopoietic lineages.

Animals↗
PubMed2001

Ski7p G protein interacts with the exosome and the Ski complex for 3'-to-5' mRNA decay in yeast.

Two cytoplasmic mRNA-decay pathways have been characterized in yeast, and both are initiated by shortening of the 3'-poly(A) tail. In the major 5'-to-3' decay pathway, the deadenylation triggers removal of the 5'-cap, exposing the transcript body for 5'-to-3' degradation. An alternative 3'-to-5' decay pathway also follows the deadenylation and requires two multi-complexes: the exosome containing various 3'-exonucleases and the Ski complex consisting of the RNA helicase Ski2p, Ski3p and Ski8p. In addition, Ski7p, which has an N-terminal domain and a C-terminal elongation factor 1alpha-like GTP-binding domain, is involved in the 3'-to-5' decay. However, physical interaction between the exosome and the Ski complex, together with the function of Ski7p, has remained unknown. Here we report that the N domain of Ski7p is required and sufficient for the 3'-to-5' decay. Furthermore, the exosome and the Ski complex interact with the different regions of Ski7p N domain, and both interactions are required for the 3'-to-5' decay. Thus, Ski7p G protein appears to function as a signal-coupling factor between the two multi-complexes operating in the 3'-to-5' mRNA-decay pathway.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Impaired synergistic activation of stress-activated protein kinase SAPK/JNK in mouse embryonic stem cells lacking SEK1/MKK4: different contribution of SEK2/MKK7 isoforms to the synergistic activation.

Stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK), which is a member of the mitogen-activated protein kinase (MAPK) family, plays an important role in a stress-induced signaling cascade. SAPK/JNK activation requires the phosphorylation of Thr and Tyr residues in its Thr-Pro-Tyr motif, and SEK1 (MKK4) and MKK7 (SEK2) have been identified as the upstream MAPK kinases. Here we examined the activation and phosphorylation sites of SAPK/JNK and differentiated the contribution of SEK1 and MKK7alpha1, -gamma1, and -gamma2 isoforms to the MAPK activation. In SEK1-deficient mouse embryonic stem cells, stress-induced SAPK/JNK activation was markedly impaired, and this defect was accompanied with a decreased level of the Tyr phosphorylation. Analysis in HeLa cells co-transfected with the two MAPK kinases revealed that the Thr and Tyr of SAPK/JNK were independently phosphorylated in response to heat shock by MKK7gamma1 and SEK1, respectively. However, MKK7alpha1 failed to phosphorylate the Thr of SAPK/JNK unless its Tyr residue was phosphorylated by SEK1. In contrast, MKK7gamma2 had the ability to phosphorylate both Thr and Tyr residues. In all cases, the dual phosphorylation of the Thr and Tyr residues was essentially required for the full activation of SAPK/JNK. These data provide the first evidence that synergistic activation of SAPK/JNK requires both phosphorylation at the Thr and Tyr residues in living cells and that the preference for the Thr and Tyr phosphorylation was different among the members of MAPK kinases.

Animals↗
PubMed2001

Complex gangliosides as cell surface inhibitors for the ecto-NAD+ glycohydrolase of CD38.

Leukocyte cell surface antigen CD38 is a single-transmembrane protein whose extracellular domain has catalytic activity for NAD(+) glycohydrolase (NADase). We previously reported that b-series gangliosides inhibit the NADase activity of the extracellular domain of CD38 expressed as a fusion protein [Hara-Yokoyama, M., Kukimoto, I., Nishina, H., Kontani, K., Hirabayashi, Y., Irie, F., Sugiya, H., Furuyama, S., and Katada, T. (1996) J. Biol. Chem. 271, 12951-12955]. In the present study, we examined the effect of exogenous gangliosides on the NADase activity of CD38 on the surface of retinoic acid-treated human leukemic HL60 cells and CD38-transfected THP-1 cells. After incubation of the cells with G(T1b), inhibition of NADase activity was observed. The time course of inhibition was slower than that of the incorporation of G(T1b) into the cells, suggesting that incorporation into the cell membranes is a prerequisite for inhibition. Inhibition occurred efficiently when G(T1b) and CD38 were present on the same cells (cis interaction) rather than on different cells (trans interaction). Although gangliosides may affect localization of cell surface proteins, indirect immunofluorescence intensity due to CD38 was not affected after G(T1b) treatment. Comparison of the effect of G(T1b) and G(D1a) indicates that the tandem sialic acid residues linked to the internal galactose residue of the gangliotetraose core are crucial to the inhibition. These results suggest a novel role of complex gangliosides for the first time as cell surface inhibitors of CD38 through specific and cis interaction between the oligosaccharide moiety and the extracellular domain.

ADP-ribosyl Cyclase↗
PubMed2001

Association of phosphatidylinositol 3-kinase composed of p110beta-catalytic and p85-regulatory subunits with the small GTPase Rab5.

A family of phosphatidylinositol 3-kinases (PI 3-kinase), comprising three major classes (I-III) in terms of substrate specificity and regulation, play important roles in a variety of cell functions. We previously reported that the class-I heterodimeric PI 3-kinase consisting of p110beta-catalytic and p85-regulatory subunits is synergistically activated by two different types of membrane receptors, one possessing tyrosine kinase activity and the other activating trimeric G proteins. Here we report an additional unique feature of the p110beta/p85 PI 3-kinase. The small GTPase Rab5 was identified as a binding protein for the p110beta-catalytic subunit in a yeast two-hybrid screening system. The interaction appears to require at least two separated amino-acid sequences present specifically in the beta isoform of p110 and the GTP-bound form of Rab5. The expressions of constitutively active and dominant negative mutants of Rab5 in THP-1 cells induce the stimulation and inhibition, respectively, of protein kinase B activity, which is dependent on the PI 3-kinase product phosphatidylinositol 3,4,5-triphosphate. These results suggest that there is a specific interaction between GTP-bound Rab5 and the p110beta/p85 PI 3-kinase, leading to efficient coupling of the lipid kinase product to its downstream target, protein kinase B.

Amino Acid Sequence↗
PubMed2001

Increase of cGMP, cADP-ribose and inositol 1,4,5-trisphosphate preceding Ca(2+) transients in fertilization of sea urchin eggs.

Transient increases, or oscillations, of cytoplasmic free Ca(2+) concentration, [Ca(2+)](i), occur during fertilization of animal egg cells. In sea urchin eggs, the increased Ca(2+) is derived from intracellular stores, but the principal signaling and release system involved has not yet been agreed upon. Possible candidates are the inositol 1,4,5-trisphosphate receptor/channel (IP(3)R) and the ryanodine receptor/channel (RyR) which is activated by cGMP or cyclic ADP-ribose (cADPR). Thus, it seemed that direct measurements of the likely second messenger candidates during sea urchin fertilization would be essential to an understanding of the Ca(2+) signaling pathway. We therefore measured the cGMP, cADPR and inositol 1,4,5-trisphosphate (IP(3)) contents of sea urchin eggs during the early stages of fertilization and compared these with the [Ca(2+)](i) rise in the presence or absence of an inhibitor against soluble guanylate cyclase. We obtained three major experimental results: (1) cytosolic cGMP levels began to rise first, followed by cADPR and IP(3) levels, all almost doubling before the explosive increase of [Ca(2+)](i); (2) most of the rise in IP(3) occurred after the Ca(2+) peak; IP(3) production could also be induced by the artificial elevation of [Ca(2+)](i), suggesting the large increase in IP(3) is a consequence, rather than a cause, of the Ca(2+) transient; (3) the measured increase in cGMP was produced by the soluble guanylate cyclase of eggs, and inhibition of soluble guanylate cyclase of eggs diminished the production of both cADPR and IP(3) and the [Ca(2+)](i) increase without the delay of Ca(2+) transients. Taken together, these results suggest that the RyR pathway involving cGMP and cADPR is not solely responsible for the initiating event, but contributes to the Ca(2+) transients by stimulating IP(3) production during fertilization of sea urchin eggs.

Adenosine Diphosphate Ribose↗
PubMed2000

Possible association of BLM in decreasing DNA double strand breaks during DNA replication.

Bloom's syndrome (BS) is a rare genetic disorder and the cells from BS patients show genomic instability and an increased level of sister chromatid exchange (SCE). We generated BLM(-/-) and BLM(-/-)/RAD54(-/-) DT40 cells from the chicken B-lymphocyte line DT40. The BLM(-/-) DT40 cells showed higher sensitivity to methyl methanesulfonate and elevated levels of SCE as expected. The targeted integration frequency was also increased remarkably in BLM(-/-) cells. The SCE frequency increase in BLM(-/-) cells was considerably reduced and the enhanced targeted integration observed in BLM(-/-) cells was almost completely abolished in BLM(-/-)/RAD54(-/-) cells, indicating that a large portion of the SCE in BLM(-/-) cells occurs via homologous recombination, and homologous recombination events increase with the defect of BLM function. The BLM(-/-)/RAD54(-/-) cells showed a slow growth phenotype and an increased incidence of chromosome-type breaks/gaps while each single mutant showed relatively small numbers of chromosome-type breaks/gaps.

Adenosine Triphosphatases↗
PubMed2000

Expression and characterization of Xenopus type I collagen alpha 1 (COL1A1) during embryonic development.

A cDNA encoding Xenopus type I collagen alpha 1 (Xenopus COL1A1) has been isolated from an ovary cDNA library. The COL1A1 cDNA is approximately 5.7 kb pairs and encodes 1447 amino acids. The putative COL1A1 polypeptide shares high identities of amino acid sequence with other vertebrate COL1A1 proteins. The level of Xenopus COL1A1 transcripts was increased markedly in the posterior region of the embryo at the tail-bud stage, then gradually spread to the anterior region. Histological observations of the tail-bud embryos showed that COL1A1 was mainly expressed in the inner layer of the posterior dorsal epidermis exposed to the somite mesoderm, except for in the dorsal fin. Less intense signals were also detected in the outer layer of the dorsal epidermis and dermatome. The expression of COL1A1 was increased in posteriorized embryos resulting from treatment with retinoic acid but decreased in hyper-dorsalized embryos resulting from lithium chloride treatment. These results suggest that COL1A1 is a major component of the dorsal dermis exposed to the somite in Xenopus embryos, but its expression is not related to the temporal sequence of somite segregation.

Amino Acid Sequence↗
PubMed2000

Crystallization and preliminary X-ray diffraction analysis of the extracellular domain of the cell surface antigen CD38 complexed with ganglioside.

The cell surface antigen CD38 is a multifunctional ectoenzyme that acts as an NAD(+) glycohydrolase, an ADP-ribosyl cyclase, and also a cyclic ADP-ribose hydrolase. The extracellular catalytic domain of CD38 was expressed as a fusion protein with maltose-binding protein, and was crystallized in the complex with a ganglioside, G(T1b), one of the possible physiological inhibitors of this ectoenzyme. Two different crystal forms were obtained using the hanging-drop vapor diffusion method with PEG 10,000 as the precipitant. One form diffracted up to 2.4 A resolution with synchrotron radiation at 100 K, but suffered serious X-ray damage. It belongs to the space group P2(1)2(1)2(1) with unit-cell parameters of a = 47.9, b = 94.9, c = 125.2 A. The other form is a thin plate, but the data sets were successfully collected up to 2.4 A resolution by use of synchrotron radiation at 100 K. The crystals belong to the space group P2(1) with unit-cell parameters of a = 57.4, b = 51.2, c = 101.1 A, and beta = 97.9 degrees, and contain one molecule per asymmetric unit with a VM value of 2.05 A(3)/Da.

ADP-ribosyl Cyclase↗
PubMed1999

Enhancement by adenosine of insulin-induced activation of phosphoinositide 3-kinase and protein kinase B in rat adipocytes.

The role of adenosine receptor in regulation of insulin-induced activation of phosphoinositide 3-kinase (PI 3-kinase) and protein kinase B was studied in isolated rat adipocytes. Rat adipocytes are known to spontaneously release adenosine, which in turn binds and stimulates the adenosine A1 receptors on the cells. In the present study, we observed that degradation of this adenosine by adenosine deaminase attenuated markedly the insulin-induced accumulation of phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), a product of PI 3-kinase. p-Aminophenylacetyl xanthine amine congener (PAPA-XAC), an inhibitor of the adenosine A1 receptor, also inhibited the insulin-induced PtdIns(3,4,5)P3 accumulation. When extracellular adenosine was inactivated by adenosine deaminase, phenylisopropyladenosine, an adenosine A1 receptor agonist, potentiated the insulin-induced accumulation of PtdIns(3,4,5)P3. Insulin-induced activation of protein kinase B, the activity of which is controlled by the lipid products of PI 3-kinase, was also potentiated by adenosine. Prostaglandin E2, another activator of a pertussis toxin-sensitive GTP-binding protein in these cells, potentiated the insulin actions. Thus, the receptors coupling to the GTP-binding protein were found to positively regulate the production of PtdIns(3,4,5)P3, a putative second messenger for insulin actions, in physiological target cells of insulin.

Adenosine↗
PubMed1999

The eukaryotic polypeptide chain releasing factor (eRF3/GSPT) carrying the translation termination signal to the 3'-Poly(A) tail of mRNA. Direct association of erf3/GSPT with polyadenylate-binding protein.

The mammalian GTP-binding protein GSPT, whose carboxyl-terminal sequence is homologous to the eukaryotic elongation factor EF1alpha, binds to the polypeptide chain releasing factor eRF1 to function as eRF3 in the translation termination. The amino-terminal domain of GSPT was, however, not required for the binding. Search for other GSPT-binding proteins in yeast two-hybrid screening system resulted in the identification of a cDNA encoding polyadenylate-binding protein (PABP), whose amino terminus is associating with the poly(A) tail of mRNAs presumably for their stabilization. The interaction appeared to be mediated through the carboxyl-terminal domain of PABP and the amino-terminal region of GSPT. Interestingly, multimerization of PABP with poly(A), which is ascribed to the action of its carboxyl-terminal domain, was completely inhibited by the interaction with the amino-terminal domain of GSPT. These results indicate that GSPT/eRF3 may play important roles not only in the termination of protein synthesis but also in the regulation of mRNA stability. Thus, the present study is the first report showing that GSPT/eRF3 carries the translation termination signal to 3'-poly(A) tail ubiquitously present in eukaryotic mRNAs.

Eukaryotic Cells↗
PubMed1999

G-protein betagamma subunit-dependent phosphorylation of 62-kDa protein in the early signaling pathway of starfish oocyte maturation induced by 1-methyladenine.

In starfish oocytes, maturation is induced by a hormone, 1-methyladenine (1-MA), that binds to the receptors exposed to the outer surface of the plasma membrane. The signal of 1-MA stimulates the heterotrimeric G protein, resulting in dissociation of the betagamma subunit of G protein (Gbetagamma) from a pertussis toxin-sensitive Gi-type alpha subunit. To investigate the targets for Gbetagamma, we analyzed 1-MA- or Gbetagamma-dependent phosphorylation using in vivo and in vitro systems. A 62-kDa protein was phosphorylated immediately after 1-MA treatment in intact oocytes. In the cell-free preparations, the 62-kDa protein was also phosphorylated on serine residue(s) immediately after addition of 1-MA or Gbetagamma. The Gbetagamma-dependent phosphorylation of the 62-kDa protein was inhibited by wortmannin or LY294002, which are mechanistically different inhibitors of phosphatidylinositol 3-kinase (PI3K). LY294002 also inhibited Gbetagamma- as well as 1-MA-induced maturation of oocytes. Taken together, these results indicate that the 62-kDa protein functions downstream of Gbetagamma and PI3K in the early signaling pathway of 1-MA-induced starfish oocyte maturation. The phosphorylation of the 62-kDa protein may be required for the activation of maturation-promoting factor.

Adenine↗
PubMed1999

Synergistic activation of a family of phosphoinositide 3-kinase via G-protein coupled and tyrosine kinase-related receptors.

Phosphoinositide 3-kinase (PI 3-kinase) is a key signaling enzyme implicated in a variety of receptor-stimulated cell responses. Stimulation of receptors possessing (or coupling to) protein-tyrosine kinase activates heterodimeric PI 3-kinases, which consist of an 85-kDa regulatory subunit (p85) containing Src-homology 2 (SH2) domains and a 110-kDa catalytic subunit (p110 alpha or p110 beta). Thus, this form of PI 3-kinases could be activated in vitro by a phosphotyrosyl peptide containing a YMXM motif that binds to the SH2 domains of p85. Receptors coupling to alpha beta gamma-trimeric G proteins also stimulate the lipid kinase activity of a novel p110 gamma isoform, which is not associated with p85, and thereby is not activated by tyrosine kinase receptors. The activation of p110 gamma PI 3-kinase appears to be mediated through the beta gamma subunits of the G protein (G beta gamma). In addition, rat liver heterodimeric PI 3-kinases containing the p110 beta catalytic subunit are synergistically activated by the phosphotyrosyl peptide plus G beta gamma. Such enzymatic properties were also observed with a recombinant p110 beta/p85 alpha expressed in COS-7 cells. In contrast, another heterodimeric PI 3-kinase consisting of p110 alpha and p85 in the same rat liver, together with a recombinant p110 alpha/p85 alpha, was not activated by G beta gamma, though their activities were stimulated by the phosphotyrosyl peptide. Synergistic activation of PI 3-kinase by the stimulation of the two major receptor types was indeed observed in intact cells, such as chemotactic peptide (N-formyl-Met-Leu-Phe) plus insulin (or Fc gamma II) receptors in differentiated THP-1 and CHO cells and adenosine (A1) plus insulin receptors in rat adipocytes. Thus, PI 3-kinase isoforms consisting of p110 beta catalytic and SH2-containing (p85 or its related) regulatory subunits appeared to function as a 'cross-talk' enzyme between the two signal transduction pathways mediated through tyrosine kinase and G protein-coupled receptors.

Amino Acid Sequence↗
PubMed1999

Inhibition of phosphodiesterase/pyrophosphatase activity of PC-1 by its association with glycosaminoglycans.

PC-1 is a type II membrane-bound glycoprotein consisting of a short N-terminal cytoplasmic domain and a large C-terminal extracellular domain, which contains phosphodiesterase/pyrophosphatase activity. When Jurkat T cells were cultured with dibutyryl cAMP, the membrane-bound PC-1 and its soluble form were induced. They were purified as a homodimer of a 130 kDa peptide and a 120 kDa monomer, respectively, and the same two forms could also be obtained from COS-7 cells that had been transfected with PC-1 cDNA. The membrane-bound and soluble forms of PC-1 were indistinguishable from each other in terms of their enzyme kinetics and N-glycosylated moieties. Thus, the enzymatically active and fully glycosylated form of soluble PC-1 was utilized to search for its interacting molecules. The phosphodiesterase/pyrophosphatase activity of PC-1 was competitively inhibited by glycosaminoglycans, such as heparin and heparan sulfate, which are the major components of the extracellular matrix. PC-1 was capable of binding to heparin-Sepharose and the binding was inhibited in the presence of the enzyme substrate, ATP or its nonhydrolyzable analog. The enzyme activity of PC-1 itself, however, was not required for the binding to heparin-Sepharose. These results suggest that PC-1 might function as an adhesion molecule independent of its enzyme activity to associate with glycosaminoglycans in the extracellular matrix.

Animals↗
PubMed1999

Defective liver formation and liver cell apoptosis in mice lacking the stress signaling kinase SEK1/MKK4.

The stress signaling kinase SEK1/MKK4 is a direct activator of stress-activated protein kinases (SAPKs; also called Jun-N-terminal kinases, JNKs) in response to a variety of cellular stresses, such as changes in osmolarity, metabolic poisons, DNA damage, heat shock or inflammatory cytokines. We have disrupted the sek1 gene in mice using homologous recombination. Sek1(-/- )embryos display severe anemia and die between embryonic day 10.5 (E10.5) and E12.5. Haematopoiesis from yolk sac precursors and vasculogenesis are normal in sek1(-/- )embryos. However, hepatogenesis and liver formation were severely impaired in the mutant embryos and E11.5 and E12.5 sek1(-/- )embryos had greatly reduced numbers of parenchymal hepatocytes. Whereas formation of the primordial liver from the visceral endoderm appeared normal, sek1(-/-) liver cells underwent massive apoptosis. These results provide the first genetic link between stress-responsive kinases and organogenesis in mammals and indicate that SEK1 provides a crucial and specific survival signal for hepatocytes.

Animals↗