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T Katada

Publications and source records attributed to T Katada.

At least 109 records · Page 6Linked to original sources
PubMed1994

G proteins activate ATP-sensitive K+ channels by antagonizing ATP-dependent gating.

To determine whether G proteins activate cardiac ATP-sensitive K+ (KATP) channels by regulating intracellular ATP (ATPi)-dependent gating, currents were measured in inside-out patches. When ATPi closed KATP channels, activators of endogenous G proteins, GTP (plus adenosine or acetylcholine), GTP gamma S, or AlF-4 stimulated channels, an effect prevented by GDP beta S. In the absence of ATPi, G protein activators were ineffective. Intracellular nucleoside diphosphates restored KATP channel openings after the "rundown" of spontaneous activity. Only when ATPi suppressed nucleoside diphosphate-induced openings, GTP gamma S or AlF-4 enhanced KATP channel activity. Active forms of exogenous G protein subunits (G alpha i-1, G alpha i-2, or G alpha o) activated only KATP channels closed by ATPi. G proteins stimulate cardiac KATP channels apparently by antagonizing ATPi-dependent inhibitory gating. Regulation of ligand-dependent gating represents a distinct type of G protein modulation of ion channels.

Acetylcholine↗
PubMed1994

Association of the beta gamma subunits of trimeric GTP-binding proteins with 90-kDa heat shock protein, hsp90.

GTP-binding proteins (G proteins), predominantly located at the inner surface of the plasma membranes of mammalian cells, dissociate into their constituent alpha and beta gamma subunits upon stimulation of G protein-coupled receptors by agonists. In the present studies, cytoplasmic proteins which might have an affinity for the dissociated beta gamma subunits were investigated by means of beta gamma subunit-immobilized affinity-column (beta gamma-immobilized column) chromatography. When soluble fractions obtained from various materials including rat liver, bovine brain, and HL-60 cells were applied to a beta gamma-immobilized column, some proteins were specifically eluted from the column with high-salt and detergent-containing solutions. One of the beta gamma subunit-binding proteins, of which the molecular weight was approximately 93,000 on SDS-PAGE, appeared to be commonly present in all tissues tested. The 93-kDa beta gamma-binding protein was identified as 90-kDa heat shock protein, hsp90, based on the findings of its partial amino acid sequences and its immunoreactivity to a monoclonal anti-hsp90 antibody. The brain hsp90 inhibited beta gamma-supported pertussis toxin-catalyzed ADP-ribosylation of alpha subunits. The hsp90 was also capable of binding to beta gamma subunits which had been reconstituted into phospholipid vesicles. The binding of hsp90 to beta gamma subunits was inhibited by the addition of GDP-bound alpha subunits, but not by GTP gamma S-bound ones. These results suggested that hsp90 could associate functionally with free beta gamma subunits dissociated from trimeric G proteins in vitro.

Adenosine Diphosphate Ribose↗
PubMed1994

Possible involvement of a pertussis toxin-sensitive GTP-binding protein in protein transport into nuclei isolated from rat liver.

Nuclear protein transport was inhibited in permeabilized HeLa cells which had been prepared after culture with pertussis toxin, suggesting that the pertussis toxin-sensitive protein(s) might be involved in the nuclear protein transport. To investigate the mechanism whereby pertussis toxin inhibited the nuclear protein transport, an accumulation of proteins containing a nuclear localization signal sequence (NLS) into isolated rat liver nuclei was investigated. The NLS-containing protein accumulation required ATP and cytosolic proteins, and was temperature- and wheat germ agglutinin-sensitive as had been observed in permeabilized cells. Non-hydrolyzable GTP analogues, such as guanosine 5'-(gamma-thio)triphosphate and guanosine 5'-(beta, gamma-methylene)triphosphate, but not ATP analogues, inhibited the NLS-containing protein accumulation in the isolated nuclei. The NLS-containing protein accumulation was also inhibited by prior treatment of the nuclei with pertussis toxin plus NAD, and the effect of pertussis toxin was blocked when guanosine 5'-(gamma-thio)triphosphate was simultaneously added during the pretreatment with pertussis toxin. The inhibition induced by pertussis toxin and the blockage by guanosine 5'-(gamma-thio)triphosphate were well correlated to ADP-ribosylation of 40-kDa protein in nuclear fraction. These results suggested that the nuclear pertussis toxin-sensitive GTP-binding protein is involved in a pathway of nuclear protein transport.

Adenosine Diphosphate Ribose↗
PubMed1994

ADP-ribosylarginine glycohydrolase catalyzing the release of ADP-ribose from the cholera toxin-modified alpha-subunits of GTP-binding proteins.

A rat glycohydrolase which catalyzes the hydrolysis of ADP-ribosylarginine was expressed in Escherichia coli and purified to homogeneity for characterization of its enzymatic properties. The purified glycohydrolase catalyzed the hydrolysis of N-glycoside linked ADP-ribosylarginine on the alpha-subunits of stimulatory GTP-binding proteins (Gs) and cholera toxin A1-subunit that had been modified by cholera toxin and NAD. Nonmuscle actin of which an arginine residue was ADP-ribosylated by botulinum C2 toxin also served as a substrate of the glycohydrolase. On the other hand, the glycohydrolase did not hydrolyze ADP-ribosylated cysteine on the alpha-subunits of pertussis toxin-substrate GTP-binding proteins, ADP-ribosylated diphthamide on elongation factor 2, or ADP-ribosylated asparagine on rho GTP-binding proteins. The rate of the reaction catalyzed by the glycohydrolase was affected by nucleotide-binding form of the ADP-ribosylated substrate proteins; the GDP-bound form of the modified Gs-alpha was more rapidly hydrolyzed than the guanosine 5'-(3-O-thio)triphosphate-bound form. Interestingly, the glycohydrolase activity was markedly inhibited by mM order concentration of ATP in addition to ADP-ribose, the product of the enzyme reaction, though ADP had no inhibitory effect on the activity. Moreover, alpha NAD, but not beta NAD, inhibited the enzyme activity, suggesting that the glycohydrolase reaction was stereospecific for the alpha-anomer.

Adenine Nucleotides↗
PubMed1994

[Structure and function of heterotrimeric G-proteins].

In mammals, G-protein alpha, beta, gamma polypeptides are encoded by at least 16, 4 and 7 genes, respectively. G alpha-subunits bind and hydrolyze GTP and have the sites for bacterial toxin-catalyzed ADP-ribosylation. A structural model of G alpha-subunits can be defined on the basis of similarities between G alpha and other members of the GTP-binding proteins. The resulting G alpha model specifies the spatial relationship among the guanine nucleotide binding site, the binding site of the G beta gamma-subunit complex, likely regions of effector and receptor interaction, and sites of cholera or pertussis toxin-induced modification. The architecture of the G alpha core is the same as that of p21ras. Experimental evidence from immunological, molecular genetic and biochemical studies support the G alpha model. The G alpha-subunits alone were previously thought to act on the effector enzymes; However, recent evidence indicates that the G beta gamma-dimer also plays an important part in effector activation.

Amino Acid Sequence↗
PubMed1993

Opposite coupling of prostaglandin E receptor EP3C with Gs and G(o). Stimulation of Gs and inhibition of G(o).

We recently identified four isoforms of bovine prostaglandin E receptor EP3 subtype, which are coupled to different signaling pathways; EP3A is coupled to inhibition of adenylate cyclase, while EP3B and EP3C are coupled to its stimulation and EP3D is coupled to phosphatidylinositol turnover, in addition to the adenylate cyclase system (Namba, T., Sugimoto, Y., Negishi, M., Irie, A., Ushikubi, F., Kakizuka, Ito, S., A., Ichikawa, A., and Narumiya, S. (1993) Nature 365, 166-170). We examined here the identity of coupled G proteins and their regulation by one of the isoforms, EP3C, in the membranes of EP3C cDNA-transfected Chinese hamster ovary cells. M&B 28767, an EP3 agonist, stimulated the GTPase activity in the pertussis toxin (PT)-treated cell membrane, but inhibited it in the cholera toxin (CT)-treated cell membrane, while the agonist neither stimulated nor inhibited it in the both PT- and CT-treated cell membrane. In the PT- and CT-treated cell membrane reconstituted with various G proteins, M&B 28767 inhibited the GTPase activity of G(o), but stimulated that of Gs. On the other hand, M&B 28767 did not affect the GTPase activity of Gi1, Gi2, or Gi3. M&B 28767 increased the apparent affinity of G(o) for GDP without any change in that for GTP, as assessed by displacement of [35S]GTP gamma S (guanosine 5'-O-(3-thiotriphosphate)) binding to G(o). In contrast, M&B 28767 increased the apparent affinity of Gs for GTP but decreased that for GDP. These results demonstrated that the EP3 receptor isoform is coupled to two different G proteins, and oppositely regulates their activities, inhibition of G(o), and stimulation of Gs.

Alprostadil↗
PubMed1993

GK* and brain G beta gamma activate muscarinic K+ channel through the same mechanism.

A pertussis toxin-sensitive G protein (GK) links muscarinic cholinergic and A1-purinergic receptors with an inwardly rectifying K+ (KACh) channel in cardiac atrial cell membranes. Although the beta gamma subunits of pertussis toxin-sensitive G proteins (G beta gamma) have been reported to fully activate this channel, it is not known whether exogenously applied G beta gamma interacts with the KACh channel through the same mechanism as the active subunit of endogenous GK (GK*). We examined in inside-out patches the relationship between the concentration of GTP and KACh channel activity with or without preactivation of the channels by either GTP gamma S (guanosine 5'-3-O-(thio)triphosphate) or G beta gamma purified from bovine brain. In the control, KACh channels were activated by intracellular GTP (with acetylcholine in the pipette) in a positive cooperative manner (Hill coefficient approximately 2.5). As the channels were preactivated by GTP gamma S to progressively higher levels, the GTP channel activity relationship shifted more to the left, but the Hill coefficients of the curves remained the same. The same changes were observed when KACh channels were preactivated with brain G beta gamma. These results indicate that endogenous GK* and exogenous G beta gamma share a common molecular mechanism to activate the KACh channel.

Animals↗
PubMed1993

Alterations of guanine nucleotide-binding proteins in post-mortem human brain in alcoholics.

Qualitative and quantitative alterations of G proteins in membrane preparations from parietal and temporal cortex regions in post-mortem brains obtained from alcoholics and controls matched with respect to age and post-mortem delay were investigated by Western-blotting with polyclonal antibodies against specific G protein subunits and functional photoaffinity GTP binding. Quantitative immunoblotting showed that only Gs alpha (52 kDa species) in temporal cortex was significantly decreased (30%, P < 0.05) in alcoholics compared with controls. Moreover, ethanol-stimulated photoaffinity GTP labeling of Gs alpha and Gi/o alpha was decreased in alcoholics in both cortex regions. These results suggest that disturbances of G protein-mediated signal transduction may be involved in the pathophysiology of alcoholics.

Aged↗
PubMed1993

NAD glycohydrolase specifically induced by retinoic acid in human leukemic HL-60 cells. Identification of the NAD glycohydrolase as leukocyte cell surface antigen CD38.

Human leukemic HL-60 cells are differentiated into granulocytic cells by retinoic acid, and this differentiation is preceded by the induction of an ecto-enzyme of NAD glycohydrolase (NADase). The NADase specifically induced by retinoic acid appeared to be encoded by human leukocyte cell surface antigen CD38 as follows. 1) There was an early expression of CD38 mRNA, together with the induction of the NADase activity, in the retinoic acid-treated HL-60 cells. 2) The time course of the expression of CD38 antigen on the cell surface was well correlated with that of the induction of NADase activity. 3) The NADase activity solubilized from the differentiated HL-60 cell membrane could be immunoprecipitated with an anti-CD38 monoclonal antibody. 4) Introduction of the CD38 cDNA into Escherichia coli cells resulted in the expression of an NADase, the activity of which was inhibited by dithiothreitol. The NADase activity in the differentiated cells was also inhibited by the reducing reagent. These results clearly indicated that the dithiothreitol-sensitive NADase activity induced by retinoic acid in HL-60 cells is attributed to the molecule of human leukocyte cell surface antigen CD38, which contains cysteine-rich cytoplasmic domain within its molecule.

ADP-ribosyl Cyclase↗
PubMed1993

Botulinum ADP-ribosyltransferase C3 induces elevation of the vitelline coat of ascidian eggs.

Botulinum exoenzyme C3 ADP-ribosylates a 23 kDa protein of unfertilized eggs of the ascidian, Halocynthia roretzi. Microinjection of C3 into the eggs induced elevation of the egg vitelline coat. Co-injection of heparin or EGTA with C3 inhibited the inducing effect of C3. The vitelline coat of eggs which had been previously co-injected with heparin and C3 was elevated by addition of calcium ionophore, but not by insemination. C3 also induced an increased formation of inositol 1,4,5-triphosphate (IP3) in ascidian egg membranes. Thus the ADP-ribosylation of small GTP-binding protein by C3 seems to be responsible for elevation of the vitelline coat of ascidian eggs through IP3 formation and intracellular calcium mobilization.

ADP Ribose Transferases↗
PubMed1993

Production of monoclonal antibodies that inhibit ADP-ribosylation of small GTP-binding proteins catalyzed by Clostridium botulinum ADP-ribosyltransferase C3.

Four monoclonal antibodies that inhibited ADP-ribosylation of 23 kDa protein(s) of ascidian eggs catalyzed by Clostridium botulinum ADP-ribosyltransferase C3 were produced. They also inhibited C3-catalyzed ADP-ribosylation of the 24 kDa protein of rat liver cytosol. By the immunoprecipitation technique, it was found that they recognized small GTP-binding proteins of ascidian eggs and mammalian brains, but did not interact with the rat brain activator of the ADP-ribosyltransferase reaction. The antibody can also immunoprecipitate recombinant Rho A irrespective as to whether the Rho A is the GDP-bound form or the GTPrS-bound form. Thus the antibodies are novel and useful tools in analyzing the physiological roles of the Rho family of GTP-binding proteins.

ADP Ribose Transferases↗
PubMed1993

Activation by G protein beta gamma subunits of beta-adrenergic and muscarinic receptor kinase.

We have shown previously that GTP-binding regulatory protein (G protein) beta gamma subunits stimulate the agonist- or light-dependent phosphorylation of muscarinic acetylcholine receptors (mAChRs) and rhodopsin by a protein kinase partially purified from porcine brain (mAChR kinase) but not the phosphorylation of rhodopsin by rhodopsin kinase (Haga, K., and Haga, T. (1992) J. Biol. Chem. 267, 2222-2227). We report here that the mAChR kinase phosphorylates beta-adrenergic receptors (beta-ARs) purified from bovine lung in an agonist-dependent manner, and the phosphorylation is also stimulated by G protein beta gamma subunits. We also report that recombinant beta-adrenergic receptor kinase 1 (beta-ARK1) expressed in COS-7 cells phosphorylates mAChRs (human m2 subtype) and rhodopsin in an agonist- or light-dependent manner, respectively, and that this phosphorylation is stimulated by G protein beta gamma subunits. By contrast, the beta gamma subunits do not stimulate the phosphorylation of mAChRs or rhodopsin by a beta-ARK1 mutant lacking a part of the carboxyl-terminal region which is present in beta-ARKs but not in rhodopsin kinase. These results indicate that the beta-ARK1 is the same as or very similar to the mAChR kinase but is distinguished from the rhodopsin kinase with respect to activation by the beta gamma subunits and that the extra carboxyl-terminal sequence in beta-ARKs is required for the stimulation by the beta gamma subunits.

Alprenolol↗
PubMed1993

Distribution of guanine nucleotide-binding protein in the brain of the reeler mutant mouse.

The localization of a GTP-binding protein (G(o)) in the cerebellar and cerebral cortex and hippocampus of the normal and reeler mutant mouse was immunohistochemically examined using affinity-purified antibody raised against the alpha subunit of G(o). Although the general distribution pattern of G(o)-immunoreactive products in the brain of the normal mouse, i.e., abundant in the neuropil but absent from neuronal cell bodies, is also seen in the reeler brain, some differences are present, as described below. Strong G(o)-immunoreactive products are found in the molecular layer of the cerebellar cortex of the normal mouse. In the reeler cerebellum, in addition to the strong G(o)-immunoreactivity of the thin molecular layer, moderate G(o)-immunoreactivities are also found in the granular cell layer and the central cerebellar mass. G(o)-immunoreactive products are distributed throughout all layers of the cerebral cortex of the normal and reeler mouse. However, layer I of the normal cerebral cortex is more strongly stained with this antibody than the underlying layers, whereas the upper third of the reeler cerebral cortex is more strongly stained than the lower two-thirds. In the hippocampus of the normal mouse, G(o)-immunoreactive products are localized in the neuropil of the stratum oriens, stratum radiatum and stratum lacunosum-moleculare, but absent from the cell bodies of the pyramidal cells and their apical dendritic shafts. Such a distribution pattern of G(o)-immunoreactive products is also seen in the hippocampus of the reeler mouse, except that G(o)-immunonegative pyramidal cells split into 2 or 3 laminae.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Somatostatin induces release of the alpha subunits of pertussis toxin-sensitive G proteins in native membranes and in intact GH4C1 rat pituitary cells.

Incubation of GH4C1 rat pituitary cell membranes with the poorly hydrolyzable GTP analogue, GTP gamma S, produces a decrease in the pertussis toxin-catalyzed ADP-ribosylation of 40-kDa protein in the membrane pellet and the release of an alpha-like substrate from the membrane into the supernatant fraction; these effects do not occur with the inactive GDP analogue, GDP beta S. The resolved supernatant fraction from GTP gamma S-stimulated membranes is significantly activated to pertussis toxin-catalyzed [32P]ADP-ribosylation by the addition of purified beta gamma complex. Immunoblot analysis identifies the released pertussis toxin substrate as alpha subunits of Gi2, Gi3, and G(o) in the resolved supernatant. The physiological agonist, somatostatin, also stimulates the release of Gi2 and G(o) alpha subunits but not Gi3 from GH4C1 cell membranes in the presence of a low concentration of GTP gamma S (20 nM). The effects of somatostatin are inhibited by pretreatment of GH4C1 cells with pertussis toxin. Furthermore, the addition of somatostatin to intact GH4C1 cells decreases the level of Gi2 alpha subunits in the crude membrane whereas immunoblot analysis of the 274,000 x g supernatant (cytosolic fraction) clearly shows the presence of Gi2 alpha subunits. These data indicate that pertussis toxin-sensitive G proteins in GH4C1 cells dissociate into alpha subunits and beta gamma complex with the release of the alpha subunits from the membranes upon somatostatin activation.

Adenosine Diphosphate Ribose↗
PubMed1993

Induction of starfish oocyte maturation by the beta gamma subunit of starfish G protein and possible existence of the subsequent effector in cytoplasm.

beta gamma subunits of G proteins were purified from starfish oocytes, and their role in the induction of oocyte maturation by 1-methyladenine was investigated. When injected into starfish oocytes, the purified beta gamma subunit of the starfish G protein induced germinal vesicle breakdown (GVBD) faster than that of bovine brain G protein. Injection of the starfish beta gamma into cytoplasm near the germinal vesicle (GV) induced GVBD earlier than when injected into the GV or the cytoplasm near the plasma membrane. Fluorescent-labeled beta gamma was retained in the injected area even after GVBD. Injected beta gamma also induced the formation of maturation-promoting factor as well as an increase of histone H1 kinase activity. These results suggest that beta gamma dissociates from alpha-subunit by the stimulation of 1-methyladenine and interacts with a cytoplasmic effector, which results in formation of active cdc2 kinase.

Adenine↗
PubMed1993

[Involvement of G protein in receptor-effector coupling].

G proteins consist of three subunits, alpha, beta and gamma, and bind with GTP or GDP to mediate the transformation and amplification of the signals between receptor on the cell membrane and the intracellular effector system (enzymes or ion channels), which produces various types of messenger. Bacterial toxins such as cholera and pertussis are widely used for research of signal transduction, owing to their ability for ADP-ribosylation of some types of G proteins to modify their functions. Network of signal transduction involving G proteins expands in cells of various organs, and relationship between G protein and receptors, or effectors, has been revealed day by day. Recent information of them are reviewed here.

Animals↗
PubMed1992

A protein kinase C inhibitor, staurosporine, activates phospholipase D via a pertussis toxin-sensitive GTP-binding protein in rabbit peritoneal neutrophils.

In rabbit peritoneal neutrophils prelabeled with [3H] lyso platelet-activating factor, a protein kinase C inhibitor, staurosporine (> 1 microM), increased [3H]phosphatidylethanol ([3H]PEt) level in the presence of ethanol in a concentration- and time-dependent manner, providing evidence for staurosporine activation of phospholipase D (PLD). The staurosporine activation of the enzyme absolutely required both extracellular calcium and cytochalasin B, and was almost completely inhibited by pretreatment of the cells with pertussis toxin (IAP). In a reconstituted system where the purified Gi1 had been incorporated into phospholipid vesicles, staurosporine activated GTPase activity of Gi1 in a concentration-dependent fashion, with a maximal 4-5-fold effect. ADP-ribosylation by IAP of Gi1 in vesicles significantly suppressed the staurosporine activation. As with the GTPase activity of Gi1, GTPase activities of other purified IAP-sensitive G proteins, such as Gi2 and G(o), were significantly stimulated by staurosporine, but the cholera toxin substrate Gs was appreciably less sensitive to the staurosporine stimulation. The staurosporine activation of GTPase was also observed in rabbit neutrophil membranes from control cells, but not in membranes from IAP-treated neutrophils. From these results, we conclude that the staurosporine activation of PLD in rabbit neutrophils is attributed to the direct activation of an IAP-sensitive G protein in a similar manner to receptors occupied by agonists. By contrast, staurosporine failed to activate phosphoinositide-specific phospholipase C (PI-PLC) under the conditions in which it activated PLD, indicating that there exists a PLD activation pathway independent of PI-PLC. Furthermore, it was found that N-acetyl-beta-glucosaminidase release from the granules of intact neutrophils was evoked by staurosporine to almost the same extent as by fMLP (100 nM), but O2- generation was not affected. These results suggest a possibility that PLD pathway plays an important role in enzyme release, but is not sufficient for O2- generation, in rabbit peritoneal neutrophils.

Acetylglucosaminidase↗