Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NG108-15 neuroblastoma x glioma hybrid cells and S49 lymphoma cells exhibit an enhancement in adenylyl cyclase activity after chronic treatment with receptor agonists that acutely inhibit the enzyme. Using agonists that activate five distinct inhibitory receptors in NG108-15 cells, we have found that there is a correlation between the extent of acute inhibition of prostaglandin E1 (PGE1)-stimulated cAMP accumulation and efficacy for induction of enhanced PGE1 stimulation of cAMP accumulation after chronic treatment and withdrawal. Chronic treatment with dideoxyadenosine, which acutely inhibits adenylyl cyclase activity by a mechanism independent or cell surface receptors or pertussis toxin-sensitive G proteins, did not induce enhanced PGE1 stimulation of cAMP accumulation in NG108-15 cells or forskolin stimulation of cAMP accumulation in S49 cells. While control basal cAMP concentrations were acutely decreased by carbachol in NG108-15 cells and by somatostatin in S49 cells, when the cAMP concentrations were maintained above the control basal values with a phosphodiesterase inhibitor, chronic treatment with these inhibitory drugs nonetheless resulted in enhanced cAMP responses in both NG108-15 and S49 cells. These results provide evidence that the initial decrement in cAMP concentrations caused by inhibitory drug is not the requisite signal for inducing the subsequent sensitization of adenylyl cyclase in NG108-15 and S49 cells but that activation of a pertussis toxin-sensitive G protein is involved in the development of this important adaptation.
 ...
PMID:Adaptive increase in adenylyl cyclase activity in NG108-15 and S49 cells induced by chronic treatment with inhibitory drugs is not due to a decrease in cyclic AMP concentrations. 132 99

Many cells develop enhanced adenylate cyclase activity after prolonged exposure to drugs that acutely inhibit the enzyme and it has been suggested that this adaptation may be due to an increase in Gs alpha. We have treated wild-type and Gs alpha-deficient cyc- S49 mouse lymphoma cells with a stable analogue (SMS 201-995) of the inhibitory agonist somatostatin. After incubation with SMS for 24 h, the forskolin-stimulated cAMP synthetic rate in intact cyc- cells was increased by 76%, similar to the increase found in the wild-type cells. Forskolin-stimulated adenylate cyclase activity in the presence of Mn2+ was also increased in membranes prepared from SMS-treated cyc- cells; however, guanine nucleotide-mediated inhibition of adenylate cyclase activity was not changed despite a small decrease in inhibitory Gi alpha subunits detected by immunoblotting. Pretreatment of cyc- cells with pertussis toxin prevented SMS from inducing the enhancement of forskolin-stimulated cAMP accumulation in intact cells. After chronic incubation of cyc- cells with SMS, exposure to N-ethylmaleimide, which abolished receptor-mediated inhibition of cAMP accumulation, did not attenuate the enhanced rate of forskolin-stimulated cAMP synthesis compared to N-ethylmaleimide-treated controls. These results with cyc- cells demonstrate that an adaptive increase in adenylate cyclase activity induced by chronic treatment with an inhibitory drug can occur in the absence of expression of Gs alpha.
 ...
PMID:Prolonged activation of inhibitory somatostatin receptors increases adenylate cyclase activity in wild-type and Gs alpha-deficient (cyc-) S49 mouse lymphoma cells. 132 4

In this study, we have used photoaffinity labeling by [32P]azido-GTP as well as [32P]ADP-ribosylation by pertussis toxin (PT) and cholera toxin (CT) to identify GTP-binding proteins associated with mouse T-lymphoma plasma membranes. Our results indicate that GP85 (CD44) can be photoaffinity labeled by [32P] azido-GTP and [32P]ADP-ribosylated by both PT and CT. Using purified GP85 (CD44) obtained by Triton X-100 extraction, wheat germ agglutinin-Sepharose, and anti-GP85 (CD44) antibody affinity chromatographies, we have further characterized GP85 (CD44) as a GTP-binding protein. GP85 (CD44) is found to bind guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) in a time- and dose-dependent manner with a dissociation constant of 0.83 nM. Importantly, GP85 (CD44) appears to display a GTPase activity which hydrolyzes [gamma-32P]GTP at a rate of 0.011 mol of Pi released/mol of GP85 (CD44)/min. This GTPase activity can be readily inhibited by PT- or CT-mediated ribosylation of GP85 (CD44). Most interestingly, GTP binding significantly enhances the interaction of purified GP85 (CD44) with ankyrin, whereas ADP-ribosylation of GP85 (CD44) by PT or CT inhibits the GTP-induced increase in ankyrin binding to GP85 (CD44). In addition to GP85 (CD44) being the first reported transmembrane GTP-binding protein, these results suggest that GTP plays an important role in promoting the interaction between GP85 (CD44) and its underlying membrane cytoskeleton through ankyrin.
 ...
PMID:The lymphoma transmembrane glycoprotein GP85 (CD44) is a novel guanine nucleotide-binding protein which regulates GP85 (CD44)-ankyrin interaction. 142 59

The Nb2 node lymphoma cell line has been widely used as a model for investigating lactogen cellular actions. Both pertussis (PTX) and cholera (CTX) toxins modulate lactogen-stimulated Nb2 cell mitogenesis, suggesting G protein involvement in lactogen signal transduction. The following studies were performed to further investigate this possibility. Both PTX-sensitive (41 kDa) and CTX-sensitive substrates (42 and 45 kDa) were identified in Nb2 cell membrane and recognized by specific anti-Gi and anti-Gs antibodies, respectively. Equal numbers of Nb2 cells were then incubated with the lactogen human growth hormone (hGH, 10 ng/ml) for 0-72 h. Membrane protein prepared from each time point (50 micrograms) was compared in toxin-stimulated ADP-ribosylation studies. CTX-stimulated ADP-ribosylation was unaffected by prior hGH incubation. PTX-stimulated ADP-ribosylation increased 237 +/- 69% (X +/- S.E.) compared with 0-h controls (n = 11; p less than 0.01) after 4-7 h of hGH incubation then decreased toward 0-h samples by 24 and 72 h. No change in Gi alpha concentration was observed, but beta subunit concentration increased (145 +/- 14% at 7 h; p less than 0.01; n = 3) in a time course that paralleled the changes in PTX-stimulated ADP-ribosylation. In summary, 1) both Gi and Gs were present in Nb2 cell membrane, 2) incubation of cells with a lactogen, hGH, for 4-7 h markedly enhanced PTX-stimulated ADP-ribosylation of Gi alpha in vitro, whereas CTX-stimulated ADP-ribosylation of Gs alpha was unchanged, and 3) although no change in Gi alpha concentration was observed, beta subunit concentration increased in parallel with the increase in PTX-stimulated ADP-ribosylation of Gi alpha. These results suggest that hGH may modify PTX-stimulated ADP-ribosylation of Gi not by changing Gi alpha concentration, perhaps by increasing beta subunit concentration, enhancing association of Gi alpha by beta gamma subunits, which, in turn, is preferentially ADP-ribosylated. This may represent a late signal transduction event and may also have implications for other effectors dependent on Gi-mediated events.
 ...
PMID:Human growth hormone enhances pertussis toxin-stimulated ADP-ribosylation of Gi in Nb2 cell membrane. 158 39

S49 mouse lymphoma cells respond to swelling deformation with rapid increases in intracellular calcium and cAMP. Experiments demonstrate that these increases in calcium and cAMP concentrations are not coupled in a regulatory manner. Direct inhibition of adenylate cyclase in wild type cells with miconazole prevented swelling-induced accumulation of cAMP. No effect of swelling was observed on the activity of cAMP phosphodiesterase. Additionally, complete inhibition of cAMP phosphodiesterase did not prevent swelling-induced cAMP accumulation. Experiments involving cyc- mutants (lacking the Gs-alpha protein) and 2',5'-dideoxyadenosine indicate that increased adenylate cyclase activity with swelling is not mediated by Gs. No evidence was found for attenuation of Gi-mediated inhibition of adenylate cyclase activity following swelling. In addition, exposure to pertussis toxin or phorbol ester, which disrupts Gi inhibition of adenylate cyclase did not prevent cAMP accumulation following swelling. Disruption of the actin membrane skeleton resulted in a significant accumulation of cAMP which was not further increased by swelling. Disruption of the microtubular cytoskeleton also increased cAMP content in S49 cells which could be further increased by swelling. It is concluded that S49 cell-adenylate cyclase responds directly to mechanical forces transmitted through the actin membrane skeleton.
 ...
PMID:Direct stimulation of adenylate cyclase by mechanical forces in S49 mouse lymphoma cells during hyposmotic swelling. 169 Nov 72

Activation of T lymphocytes leads to the production of the T cell growth factor IL-2 that regulates T cell proliferation. This activation is associated with several potential intracellular signalling events including increased activity of phospholipase C (PLC) and resultant increases in production of inositol phosphates and diacylglycerols. In addition, phosphorylation of specific intracellular proteins on serine, threonine, and tyrosine residues increases. The role of each of these events in IL-2 production is unclear. Using Western blotting with antiphosphotyrosine antibodies, we demonstrate that activation of murine T cells with mitogenic lectins or anti-CD3 antibodies leads to a rapid increase in tyrosine phosphorylation of proteins of 120, 72, 62, 55, and 40 kDa. Similar patterns of antiphosphotyrosine antibodies reactivity were observed in splenocytes, a T cell hybridoma, and a T lymphoma. Tyrosine phosphorylation was detectable within minutes of addition of mitogenic lectins and persisted for at least 6 h. Pretreatment of the cells with pertussis toxin did not inhibit tyrosine phosphorylation indicating that a pertussis toxin-sensitive G protein is not involved in signal transduction. Neither increasing cytosolic-free calcium nor activating protein kinase C mimicked the effects of mitogenic lectins suggesting that tyrosine phosphorylation was not a consequence of activation of PLC. This was confirmed by demonstrating that mitogenic lectins induced similar patterns of tyrosine phosphorylation in cells in which activation of the TCR leads to increased PLC activity and in cells in which PLC is not stimulated. To test whether tyrosine phosphorylation is linked to IL-2 secretion, we determined the effect of three specific tyrosine kinase inhibitors (tyrphostins) on tyrosine phosphorylation, IL-2 secretion, and cellular proliferation. The concentration dependence of inhibition of tyrosine phosphorylation and IL-2 production were similar. However, higher concentrations of the tyrphostins were required to inhibit constitutive proliferation of the T cell line indicating that inhibition of IL-2 secretion was not secondary to nonspecific toxic effects of the tyrphostins. Addition of the tyrphostins after mitogenic lectin decreased the amount of tyrosine phosphorylation and IL-2 secretion in parallel. This indicates that both tyrosine kinases and phosphatases are activated and that continuous tyrosine phosphorylation is likely required for IL-2 secretion. Therefore, tyrosine phosphorylation appears to represent an obligatory event in the transmembrane signaling processes that lead to IL-2 secretion.
 ...
PMID:Tyrosine phosphorylation is an obligatory event in IL-2 secretion. 169 78

Ontogeny of trimeric GTP-binding regulatory proteins (G-proteins) and their subunits in rabbit liver during neonatal development was studied, by using bacterial-toxin-catalysed ADP-ribosylation of membrane proteins, immunoblot analysis to quantify the alpha-subunit (alpha s and alpha i) of stimulatory (Gs) and inhibitory (Gi) G-protein and the beta-subunit, and reconstitution assay with cyc- membranes (from Gs-deficient variant of S49 lymphoma cell) to measure Gs activity. Under optimal conditions of ADP-ribosylation, little cholera-toxin substrate (alpha s) was detected in membranes from liver of neonatal animals up to 24 h of age. Thereafter ribosylatable alpha s proteins, i.e. 45 kDa (alpha s-1) and 52 kDa (alpha s-2) proteins, were increasingly evident, reaching maximal levels in membranes from animals aged 4-6 weeks. The concentrations of alpha s-1 and alpha s-2, as determined by immunoblotting, were 6.1 +/- 0.8 and 2.7 +/- 0.4 pmol/mg of protein respectively at birth, and did not change during 0-24 h after birth. Thereafter they gradually increased to maximal levels of 22.1 +/- 1.3 and 10.5 +/- 0.7 pmol/mg of protein for alpha s-1 and alpha s-2 respectively, within 6 weeks. The beta-subunit also showed a similar 3-4-fold increase during the same age span. In contrast, the pertussis-toxin substrate (alpha i) was clearly evident even in membranes from term animals and in all age groups studied. Its developmental pattern, as assessed by ADP-ribosylation, was the same as that determined by immunoblot analysis. The functional activity of Gs in cholate extracts of membranes exhibited similar developmental pattern to that of cholera-toxin-mediated labelling. This activity also paralleled the concentrations of alpha s as measured by immunoblotting. These results suggest differential expression of G-protein subunits in liver during neonatal development.
 ...
PMID:Ontogeny of guanine-nucleotide-binding regulatory proteins in rabbit liver. 190 Sep 88

Pertussis toxin is known to elicit lymphocytosis in whooping cough patients and experimental animals, by blocking the extravasation of lymphocytes and stimulating their release from lymphoid organs such as the thymus. The mechanisms responsible for these unique effects of PT are not fully understood. The effect of pertussis toxin (PT) on the invasive behavior of human CCRF-CEM T lymphoma cells has been investigated with the use of a monolayer invasion assay (MIA). We had previously found that invasion of murine T lymphoma cells in this model system was correlated with their ability to extravasate and form metastases after i.v. injection in syngeneic animals. We now show that human CEM cells can also penetrate through a precultured confluent monolayer of murine 10T1/2 fibroblast-like cells within a few hours. In a quantitative MIA run over 24 h, PT at concentrations above 10(-14) M inhibited invasion of the CEM cells. In addition, PT stimulated the release ('evasion') of CEM cells that had invaded under the monolayer before the toxin was added. The A subunit of PT was totally inactive, the B subunit had a small residual effect, and reconstitution of the AB complex partially restored the activity. The invasion-inhibiting activity of two different holotoxin preparations and of the subunits perfectly matched their activity in the Chinese hamster ovary cell clustering assay, which is known to depend on a functional AB complex. We suggest that inhibition of monolayer invasion by PT can be used as an in vitro model system to investigate the cellular and molecular mechanisms underlying the lymphocytosis-promoting action of the toxin. Furthermore, the method is sufficiently sensitive to be used for titration of toxin activity. Our data indicate that the ADP-ribosylating activity of the A subunit is indeed required, and that the promotion of lymphocytosis is not elicited by the binding of the B subunit alone.
 ...
PMID:The lymphocytosis promoting action of pertussis toxin can be mimicked in vitro. Holotoxin but not the B subunit inhibits invasion of human T lymphoma cells through fibroblast monolayers. 196 Apr 20

Some beta-adrenergic receptor (beta AR) antagonists, in addition to blocking receptor-mediated responses, possess agonistic properties or intrinsic sympathomimetic activity (ISA). In this study we describe several techniques for amplification of cAMP levels as a measure of agonistic activity, and we apply these techniques to the study of beta AR antagonists with ISA. We show that 1) a variety of beta AR antagonists with ISA, including alprenolol and cyanopindolol, enhance cyclic AMP accumulation in S49 lymphoma cells if cells are also incubated with the diterpene forskolin; 2) beta AR blockers with ISA stimulate cAMP accumulation in the presence of a water-soluble analog of forskolin but not in the presence of 9,11-dideoxyforskolin (which does not activate adenylyl cyclase); 3) the potentiation by forskolin is not unique to S49 cells but is also observed in BC3H1 smooth muscle-derived cells; 4) stimulation of cAMP accumulation by beta-blockers with ISA occurs in S49 cells in three additional settings that do not involve the use of forskolin, after pretreatment with pertussis toxin to inactivate the inhibitory guanine nucleotide binding protein, after pretreatment with [D-Trp8]-somatostatin to sensitize adenylyl cyclase, and using a radioimmunoassay to quantitate levels of cellular cAMP. We conclude that beta AR antagonists with ISA can weakly stimulate intracellular cAMP accumulation, but this stimulation is not easily detected. Elevation of cAMP levels may account for the agonistic effects of these drugs or, at least provides a measure of stimulatory guanine nucleotide-binding protein activation by these compounds.
 ...
PMID:Amplification of cyclic AMP generation reveals agonistic effects of certain beta-adrenergic antagonists. 196 18

In this study we have used several complementary techniques to isolate and characterize a lymphoma membrane-associated 41-kDa protein that shares a number of structural and functional similarities with the alpha i subunit of the guanosine 5'-triphosphate (GTP)-binding protein (e.g., Gi alpha-like protein). In addition, using permeabilized lymphoma cells, we have found that: 1) GTP or GTP-tau-S augments, and pertussis toxin inhibits, phospholipase C (PLC) activity and receptor capping; and 2) the addition of lymphoma 41-kDa Gi alpha-like protein stimulates PLC activity and receptor patching/capping, and reverses the inhibitory effect of pertussis toxin on both activity and receptor patching/capping. Additional cytochemical and biochemical data indicate that the lymphoma 41-kDa protein is closely associated with several cytoskeletal proteins (e.g., actin, myosin, and fodrin) all of which colocalize under receptor cap structures. Furthermore, both the 41-kDa-mediated phospholipase C activity and receptor patching/capping are inhibited by cytochalasin D (a microfilament disrupting drug) and W-7 drug (a calmodulin inhibitor). Together, these data provide strong evidence for a functional association between the lymphoma membrane cytoskeleton and the 41-kDa (Gi alpha-like) protein. Specifically, this association appears to be required for the activation of phospholipase C that results in inositol triphosphate production, subsequent internal Ca2+ release, and finally surface receptor patching and capping.
 ...
PMID:Interactions between a lymphoma membrane-associated guanosine 5'-triphosphate-binding protein and the cytoskeleton during receptor patching and capping. 196 26


1 2 3 4 5 6 7 8 Next >>