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D L Burns

Publications and source records attributed to D L Burns.

At least 73 records · Page 4Linked to original sources
PubMed1987

Immune response to the B oligomer of pertussis toxin.

Immunization of mice with the B oligomer of pertussis toxin induced antibodies to the native toxin as measured by an enzyme-linked immunosorbent assay. These antibodies neutralized the ability of pertussis toxin to alter the morphology of Chinese hamster ovary cells. Furthermore, mice immunized with the B oligomer, when challenged with pertussis toxin, did not exhibit the leukocytosis normally associated with exposure to the toxin. These results demonstrate that the B oligomer, which does not contain the enzymatic activity of the holotoxin, can be used to induce a neutralizing antibody response and suggest that the B oligomer might be considered for use in acellular pertussis vaccines.

Animals↗
PubMed1987

Dissociated cingulate cortical neurons: morphology and muscarinic acetylcholine receptor binding properties.

Identifiable cortical neurons were obtained from area 29c of rat cingulate cortex using enzymatic and mechanical dissociation techniques. Dissociated neurons were either analyzed morphologically with the electron microscope or processed autoradiographically to evaluate the distribution of specific 3H-propylbenzilylcholine mustard (PrBCM) binding. Ultrastructurally, neurons appeared healthy and contained a full complement of cytoplasmic organelles. Membranes were intact and no presynaptic endings adhered to cell bodies or dendrites. Dendritic spines were not observed in these dissociations and serial sections of identified neurons indicated that all dendritic processes were smooth. Receptor binding studies were conducted on small and medium-to-large pyramidal neurons and multipolar cells. Specific binding of PrBCM was determined by calculating the mean number of grains/10 micron somal perimeter or dendritic length and subtracting mean values from a matched series of neurons that were coincubated in atropine. Specific binding was to somata and dendrites of all neurons. Nonspecific binding was an average of 33% of total binding. A 2 X 2 factorial analysis of variance comparing total and nonspecific binding for pairs of processes indicated that there were no regional differences in dendritic binding, either by cell type or by order of dendritic branching. Both somatic and dendritic PrBCM binding was antagonized by pirenzepine (PZ); however, PZ appeared to be more effective at secondary dendritic, rather than at somatic and primary apical dendritic sites. Thus, the IC50 values for somata and primary apical dendrites of small pyramids were 6 X 10(-7) and 9 X 10(-7) M PZ, respectively, while that for secondary basal dendrites of the same neurons was 5.8 X 10(-8) M. Morphological and pharmacological results together suggest that (1) muscarinic receptors are present on the smooth surfaces of all pyramidal and multipolar neurons; (2) many of the binding sites are high affinity, PZ-sensitive, M1 receptors; and (3) this binding is associated with the postsynaptic specialization of symmetric, cholinergic synapses.

Animals↗
PubMed1986

Stimulation of the thiol-dependent ADP-ribosyltransferase and NAD glycohydrolase activities of Bordetella pertussis toxin by adenine nucleotides, phospholipids, and detergents.

Pertussis toxin catalyzed ADP-ribosylation of the guanyl nucleotide binding protein transducin was stimulated by adenine nucleotide and either phospholipids or detergents. To determine the sites of action of these agents, their effects were examined on the transducin-independent NAD glycohydrolase activity. Toxin-catalyzed NAD hydrolysis was increased synergistically by ATP and detergents or phospholipids; the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) was more effective than the nonionic detergent Triton X-100 greater than lysophosphatidylcholine greater than phosphatidylcholine. The A0.5 for ATP in the presence of CHAPS was 2.6 microM; significantly higher concentrations of ATP were required for maximal activation in the presence of cholate or lysophosphatidylcholine. In CHAPS, NAD hydrolysis was enhanced by ATP greater than ADP greater than AMP greater than adenosine; ATP was more effective than MgATP or the nonhydrolyzable analogue adenyl-5'-yl imidodiphosphate. GTP and guanyl-5'-yl imidodiphosphate were less active than the corresponding adenine nucleotides. Activity in the presence of CHAPS and ATP was almost completely dependent on dithiothreitol; the A0.5 for dithiothreitol was significantly decreased by CHAPS alone and, to a greater extent, by CHAPS and ATP. To determine the site of action of ATP, CHAPS, and dithiothreitol, the enzymatic (S1) and binding components (B oligomer) were resolved by chromatography. The purified S1 subunit catalyzed the dithiothreitol-dependent hydrolysis of NAD; activity was enhanced by CHAPS but not ATP. The studies are consistent with the conclusion that adenine nucleotides, dithiothreitol, and CHAPS act on the toxin itself rather than on the substrate; adenine nucleotides appear to be involved in the activation of toxin but not the isolated catalytic unit.

Adenine Nucleotides↗
PubMed1986

Adenine nucleotides promote dissociation of pertussis toxin subunits.

Pertussis toxin is composed of an enzymatically active A subunit and a binding component (B oligomer). Both the holotoxin and the isolated A subunit have previously been shown to exhibit NAD glycohydrolase activity although the A subunit is more active on a molar basis than the holotoxin. We have investigated the mechanism by which ATP stimulates the activity of this toxin. Since dissociation of pertussis toxin subunits would result in increased NAD glycohydrolase activity, the ability of ATP to promote release of the A subunit from the B oligomer was examined. In the presence of the zwitterionic detergent 3-(3-cholamidopropyldimethyl)-1-ammonio)-propanesulfonate, concentrations of ATP as low as 1 microM promoted subunit dissociation. The concentration of ATP required for release of the A subunit was similar to that required for stimulation of NAD glycohydrolase activity. Both ATP and ADP promoted subunit dissociation and stimulated NAD glycohydrolase activity. In contrast, AMP and adenosine did not alter NAD glycohydrolase activity or affect subunit structure. The ability of ATP to decrease the affinity of the A subunit for the B oligomer may play a role in nucleotide stimulation of pertussis toxin activity.

Adenine Nucleotides↗
PubMed1985

ADP-ribosylation of transducin by pertussis toxin.

Transducin, the guanyl nucleotide-binding regulatory protein of retinal rod outer segments that couples the photon receptor, rhodopsin, with the light-activated cGMP phosphodiesterase, can be resolved into two functional components, T alpha and T beta gamma. T alpha (39 kDa), which is [32P]ADP-ribosylated by pertussis toxin and [32P]NAD in rod outer segments and in purified transducin, was also labeled by the toxin after separation from T beta gamma (36 kDa and approximately 10 kDa); neither component of T beta gamma was a pertussis toxin substrate. Labeling of T alpha was enhanced by T beta gamma and was maximal at approximately 1:1 molar ratio of T alpha : T beta gamma. Limited proteolysis by trypsin of T alpha in the presence of guanyl-5'-yl imidodiphosphate (Gpp(NH)p) resulted in the sequential appearance of proteins of 38 and 32 kDa. The amino terminus of both 38- and 32-kDa proteins was leucine, whereas that of T alpha could not be identified and was assumed to be blocked. The 32-kDa peptide was not a pertussis toxin substrate. Labeling of the 38-kDa protein was poor and was not enhanced by T beta gamma. Trypsin treatment of [32P]ADP-ribosyl-T alpha produced a labeled 37-38-kDa doublet followed by appearance of radioactivity at the dye front. It appears, therefore, that, although the 38-kDa protein was poor toxin substrate, it contained the ADP-ribosylation site. Without rhodopsin, labeling of T alpha (in the presence of T beta gamma) was unaffected by Gpp(NH)p, guanosine 5'-O-(thiotriphosphate) (GTP gamma S), GTP, GDP, and guanosine 5'-O-(thiodiphosphate) (GDP beta S) but was increased by ATP. When photolyzed rhodopsin and T beta gamma were present, Gpp(NH)p and GTP gamma S decreased [32P]ADP-ribosylation by pertussis toxin. Thus, pertussis toxin-catalyzed [32P]ADP-ribosylation of T alpha was affected by nucleotides, rhodopsin and light in addition to T beta gamma. The amino terminus of T alpha, while it does not contain the pertussis toxin ADP-ribosylation site, appeared critical to its reactivity.

Adenosine Diphosphate Ribose↗
PubMed1985

Effects of pertussis toxin on cAMP and cGMP responses to carbamylcholine in N1E-115 neuroblastoma cells.

As noted previously, in N1E-115 neuroblastoma cells, carbamylcholine, a muscarinic cholinergic agonist, increased cGMP over 15-fold and decreased basal and prostaglandin E1 (PGE1)-stimulated cAMP content. In contrast to the stimulatory effects of PGE1 on cAMP, which were immediate, the carbamylcholine-induced decrease in basal and PGE1-stimulated cAMP exhibited a delay. The delay in carbamylcholine inhibition was independent of the extent of adenylate cyclase activation. Although basal cAMP content was suppressed within 30 sec after addition of carbamylcholine, inhibition was not maximal for at least 2 min following agonist addition; the delay was similar in cells exposed to PGE1 for 10 min prior to carbamylcholine but could be eliminated by incubation of the cells with muscarinic cholinergic agonist for 5 min prior to addition of prostaglandin. N1E-115 neuroblastoma cells possess a 41,000-Da membrane protein believed to be a component of the inhibitory GTP-binding protein of adenylate cyclase that is ADP ribosylated by pertussis toxin. Incubation of the cells with pertussis toxin prior to the addition of carbamylcholine reduced the maximal extent of inhibition of cAMP content and prevented the [32P]ADP-ribosylation of a 41,000-Da protein by toxin and [32P]NAD in membrane preparations from these cells. Incubation of cells with pertussis toxin, however, did not significantly alter the dose-response curve for carbamylcholine effects on cGMP. Even high concentrations of carbamylcholine, effective in stimulating cGMP, had minimal effects on cAMP content in toxin-treated cells; thus, ADP-ribosylation of Gi converts the adenylate cyclase but not the guanylate cyclase system to an agonist-insensitive state.

Adenylate Cyclase Toxin↗
PubMed1984

Inhibition of bovine rod outer segment GTPase by Bordetella pertussis toxin.

Incubation of photolyzed bovine rod outer segment (ROS) membranes with pertussis toxin led to an inhibition of GTPase activity in an NAD-dependent reaction. In the presence of [32P]NAD, pertussis toxin catalyzed the [32P]ADP-ribosylation of a 39-kDa ROS protein and the 39-kDa alpha-subunit of transducin purified from ROS membranes. The decrease in GTPase activity was paralleled by an increase in the extent of [32P]ADP-ribosylation of the 39-kDa ROS protein. [32P]ADP-ribosylation of the 39-kDa protein occurred in both photolyzed and dark ROS membranes. Neither ATP nor guanylyl imidodiphosphate were required for either ADP-ribosylation or inhibition of GTPase. It was demonstrated previously that choleragen catalyzed the NAD-dependent inhibition of ROS GTPase (Abood, M. E., Hurley, J. B., Pappone, M-C., Bourne, H. R., and Stryer, L. (1982) J. Biol. Chem. 257, 10540-10543). Choleragen-catalyzed inhibition of GTPase and [32P]ADP-ribosylation of the 39-kDa protein required guanylyl imidodiphosphate and did not occur in dark ROS membranes. The effects of choleragen and pertussis toxin were not additive. Incubation of ROS with choleragen or pertussis toxin prevented the subsequent [32P]ADP-ribosylation by the homologous but not the heterologous toxin, consistent with the hypothesis that the two toxins act at different sites on the 39-kDa protein. Pertussis toxin is known to ADP-ribosylate the inhibitory guanine nucleotide-binding subunit of adenylate cyclase (Ni) but not the stimulatory subunit (Ns); choleragen is known to ADP-ribosylate Ns but not Ni. Since both toxins ADP-ribosylate the same subunit of transducin, it appears that this protein may possess characteristics of both Ns and Ni.

Adenosine Diphosphate Ribose↗
PubMed1984

Pertussis toxin-catalyzed ADP-ribosylation: effects on the coupling of inhibitory receptors to the adenylate cyclase system.

The adenylate cyclase system consists of stimulatory and inhibitory hormone and drug receptors coupled through different GTP-binding proteins to a catalytic unit, responsible for the synthesis of cAMP from ATP. Pertussis toxin blocks the effect of inhibitory agonists on the catalytic unit by enzymatically inactivating the inhibitory GTP-binding protein (Gi). Study of the inhibitory arm of the cyclase system has been facilitated by the dissection of the overall process of hormonal inhibition of cAMP formation into a series of reactions characteristic of the individual protein components of this complex system; pertussis toxin has proven to be a useful tool with which to study these individual reactions. Exposure of cells or membranes to pertussis toxin in the presence of NAD results in ADP-ribosylation of a 41,000 Da subunit of Gi. ADP-ribosylation of Gi has a number of effects on the overall and partial reactions of the cyclase system, including a loss of a) hormonal inhibition of cAMP formation, b) hormonal stimulation of GTPase and c) agonist-induced release of membrane-bound guanyl nucleotides. In addition, in toxin-treated membranes, the affinity of inhibitory receptors for agonist but not antagonist is decreased with no significant change in receptor number.

Adenosine Diphosphate↗
PubMed1984

NIH conference. Cyclic nucleotides: mediators of bacterial toxin action in disease.

In several bacterial diseases, the clinical, laboratory, and histologic findings result from the elaboration by the organism of a toxic product that binds to and may enter the host cell to alter its metabolism. In some cases, the intracellular mediators of toxin action are the cyclic nucleotides, cyclic adenosine 5'-monophosphate (cAMP) and cyclic guanosine 5'-monophosphate (cGMP), the ubiquitous second messengers through which numerous hormones, neurotransmitters, and drugs exert their effects. Certain toxins act by enhancing the activity of cellular enzymes that synthesize cAMP or cGMP; and others, by themselves catalyzing cAMP synthesis after entering the cell. Studies of the mechanism of action of these toxins have helped in deciphering the enzymatic components within animal cells that are responsible for cyclic nucleotide synthesis, degradation, and function as well as in understanding the pathogenesis of the diseases in which they are involved.

Adenosine Diphosphate Ribose↗
PubMed1983

Activation by thiol of the latent NAD glycohydrolase and ADP-ribosyltransferase activities of Bordetella pertussis toxin (islet-activating protein).

Pertussis toxin (islet-activating protein) activates adenylate cyclase in susceptible cells by ADP-ribosylating an inhibitory component of the cyclase system. This toxin, assayed in a cell-free system in the presence of high concentrations of thiol, catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide. This NAD glycohydrolase activity co-chromatographed on Sephacryl G-200 in 6.5 M urea, pH 3.2, 0.1 M glycine with the ADP-ribosyltransferase activity of the toxin, as monitored by the transfer of [32P]ADP-ribose from [32P]NAD to a 41,000-Da protein in NG108-15 neuroblastoma X glioma hybrid cells. In the absence of thiol, the native holotoxin was enzymatically inactive. Following addition of 250 mM dithiothreitol to the assay, maximal enzymatic activity was evident after a delay of approximately 1 h; with 20 mM thiol, the delay was longer. The Km for NAD with the fully activated enzyme was 25 microM; the Km did not appear to vary with the extent of activation. Thiol was necessary in a cell-free system to demonstrate NAD glycohydrolase activity. When extensively washed membranes were used as a source of 41,000-Da substrate, thiol was necessary to observe ADP-ribosylation in some cases (human erythrocytes) and significantly stimulated activity in others (NG108-15 cells). In contrast to the bacterial toxins choleragen and Escherichia coli heat-labile enterotoxin that ADP-ribosylate stimulatory components of the cyclase system, pertussis toxin did not transfer ADP-ribose to low molecular weight guanidino compounds, such as arginine or agmatine.

Adenosine Diphosphate Ribose↗
PubMed1983

Pertussis toxin inhibits enkephalin stimulation of GTPase of NG108-15 cells.

In neuroblastoma-glioma (NG108-15) hybrid cells, opiates inhibit adenylate cyclase and stimulate a low Km GTPase. It has been postulated that the stimulation of GTPase plays a role in opiate inhibition of adenylate cyclase (Koski, G., and Klee, W. A. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 4185-4189). Treatment of NG108-15 cells with pertussis toxin attenuates receptor-mediated inhibition of adenylate cyclase. The toxin acts by catalyzing the ADP-ribosylation of a 41,000-dalton substrate believed to be a part of the receptor-adenylate cyclase complex. We have found that toxin treatment of NG108-15 results in inhibition of the opiate-stimulated GTPase. The concentration of toxin required for inhibition of this GTPase was similar to that needed for both attenuation of opiate inhibition of adenylate cyclase and ADP ribosylation of the 41,000-dalton substrate. Inhibition of the opiate-induced GTPase by pertussis toxin in isolated membranes required NAD, consistent with the hypothesis that this effect of the toxin resulted from ADP ribosylation of a protein component of the system. Since the opiate-stimulated GTPase is believed to play a role in the receptor-mediated decrease in adenylate cyclase activity, inhibition of this GTPase may be an important part of the mechanism by which the toxin interferes with opiate action on adenylate cyclase.

Adenosine Diphosphate Ribose↗
PubMed1983

Release of guanyl nucleotides from the regulatory subunit of adenylate cyclase.

Choleragen and beta-adrenergic agonists, both of which activate turkey erythrocyte adenylate cyclase, have been reported to accelerate release of bound [3H]guanyl nucleotides from turkey erythrocyte membranes. We have now obtained evidence that choleragen- or isoproterenol-stimulated release reflects a change in the affinity of the regulatory subunit (G/F) of adenylate cyclase for guanyl nucleotides. Solubilized preparations of turkey erythrocytes that had bound radiolabeled GTP were chromatographed on Ultrogel AcA 34. The protein from which guanyl nucleotide was released upon incubation with choleragen or isoproterenol was co-eluted with G/F activity. Furthermore, this protein appears to be the same size as the complex containing the 42,000-dalton peptide, ADP*-ribosylated by choleragen, which is presumably a subunit of G/F. ADP ribosylation of the 42,000-dalton subunit of G/F by choleragen occurred with a half-time of about 5 min, whereas choleragen-stimulated release of guanyl nucleotides was much slower (t1/2 greater than or equal to 60 min). When membranes were treated with choleragen and NAD, the delay in activation of adenylate cyclase by guanylyl imidodiphosphate was decreased but not abolished, a finding consistent with the idea that release of endogenously bound nucleotide (and subsequent binding of the nonhydrolyzable GTP analog) occurs only slowly following ADP ribosylation. In contrast, activation of the adenylate cyclase of either toxin-treated or untreated membranes in the presence of isoproterenol and guanylyl imidodiphosphate was very rapid. These data support the hypothesis that isoproterenol and choleragen may activate adenylate cyclase, at least in part, by increasing the rate of release of guanyl nucleotides from G/F.

Adenylyl Cyclases↗
PubMed1982

Assembly of the catalytic trimers of aspartate transcarbamoylase from unfolded polypeptide chains.

In an effort to stimulate the in vivo formation of active enzyme from newly synthesized polypeptide chains, we have studied the in vitro assembly of the active catalytic subunits of aspartate transcarbamoylase from unfolded polypeptide chains. Hydrodynamic and spectroscopic measurements showed that incubating the catalytic trimers in 4.7 M urea for 45 min at 9 degrees C produced unfolded polypeptide chains largely devoid of the secondary and tertiary structures characteristic of native subunits. Dilution of the urea solutions led to the slow restoration of enzyme activity and the formation of trimers at a rate which could be measured quantitatively by a hybridization technique using succinylated polypeptide chains as a "chase" to "stop" the assembly. Kinetic studies showed that reactivation and assembly of trimers were coincident with a half-time for completion of about 50 min at 0 degrees C. Also, the rate-limiting reaction was first order. Although these results suggest that chain folding is the slow process, spectroscopic studies indicated that large changes in the environments of the aromatic amino acid residues occur very rapidly. Indeed the changes in the absorption spectrum are largely complete before significant reactivation and trimer formation occur. The results are consistent with an assembly mechanism in which the first step is the rapid collapse of the expanded randomly coiled chains to give partially folded monomers. These monomers are not enzymically active and cannot associate to form trimers until a rate-limiting conformational change occurs. Subsequent to this slow process, the "competent" monomers associate via a series of reactions to form active trimers.

Aspartate Carbamoyltransferase↗
PubMed1982

Choleragen-stimulated release of guanyl nucleotides from turkey erythrocyte membranes.

Choleragen stimulates adenylate cyclase by ADP ribosylating a guanyl nucleotide-binding regulatory protein (G/F). beta-Adrenergic hormones also activate the adenylate cyclase of turkey erythrocytes, and it is currently believed that they do so in part by decreasing the affinity of G/F factor for GDP, an effect which is manifested by a hormone-stimulated release of guanyl nucleotides from the membranes. Since choleragen might also activate adenylate cyclase by a similar mechanism, the effect of toxin treatment on the release of guanyl nucleotides from turkey erythrocyte membranes was examined. In the presence of NAD, choleragen was found to stimulate release of guanyl nucleotides from membranes which had been preloaded with radiolabeled GTP. No stimulation of release was observed with cAMP or when NAD was replaced by NADP, which does not serve as a substrate for choleragen-catalyzed ADP ribosylation. While either isoproterenol or choleragen can stimulate release of guanyl nucleotides from the membranes, the amount of guanyl nucleotide released in the presence of both isoproterenol and choleragen was no greater than that released by isoproterenol alone. Furthermore, when membranes were first treated with choleragen and NAD, the subsequent release of guanyl nucleotides induced by isoproterenol was reduced to approximately 15% of that observed with membranes not treated with the toxin. Therefore, choleragen may enhance release of guanine nucleotides from sites on the membranes that are also affected by beta-adrenergic agonists, sites which are thought to correspond to G/F. These data are consistent with the hypothesis that choleragen may stimulate adenylate cyclase, in part, by enhancing release of guanyl nucleotides, a mechanism similar to that of beta-adrenergic agonists.

Animals↗
PubMedDate not supplied

Prospects for a new acellular pertussis vaccine.

A number of virulence factors of Bordetella pertussis have been isolated and studied for their roles in pathogenesis and are under consideration, singly and in combinations, for inclusion in candidate acellular pertussis vaccines to be used in clinical trials to demonstrate safety and efficacy. Prospective immunogens would include lymphocytosis-promoting factor, agglutinogens, adenylate cyclase, filamentous haemagglutinin, heat-labile toxin and tracheal cytotoxin. Some of these factors are toxins and would need to be properly toxoided before being formulated into a vaccine. Clinical trials with acellular pertussis vaccines are planned or in progress in several countries.

Adenylate Cyclase Toxin↗