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

Adenosine receptors of the A1 and A2 subtypes were characterized in membranes from DDT1 MF-2 smooth muscle cells. These cells possess a high density of A1 adenosine receptors (Bmax = 0.8-0.9 pmol/mg of protein), as measured by both agonist and antagonist radioligands. Agonists compete for [125I]N6-[2-(4-amino-3-iodophenyl)ethyl]-adenosine (A1 receptor-selective radioligand) binding with the following potency series: (R)-phenylisopropyladenosine [(R)-PIA] greater than 5'-N-ethylcarboxamide adenosine (NECA) greater than (S)-PIA, indicative of their interaction with A1 adenosine receptors. Agonist competition for [3H]8-(4-[[[(2-aminoethyl)amino]carbonyl)methyl)oxy]phenyl)-1, 3-dipropylxanthine [( 3H]XAC) (an antagonist radioligand for the A1 adenosine receptor) was described by a two-state model of 1.3 nM (high affinity state, KK) and 370 nM (low affinity state, KL), with 70% of the receptors in the high affinity state (RH). Addition of guanosine 5'-[beta, alpha-imido]triphosphate (100 microM) shifted the (R)-PIA competition curves to the right to lower affinities. Photoaffinity labeling with the agonist photoprobe [125I]N6-[2-(4-amino-3-iodophenyl) ethyl]adenosine indicates that the A1 adenosine receptor binding subunit is a Mr 38,000 protein. Adenosine receptor agonists [(R)-PIA, NECA, and (S)-PIA] inhibited isoproterenol-stimulated adenylate cyclase activity in DDT1 MF-2 cell membranes with IC50 values of 62, 538, and 750 nM, respectively. Inhibition of adenylate cyclase by (R)-PIA was attenuated by the A1 receptor antagonist XAC and following inactivation of Gi with pertussis toxin (100 ng/ml). Using a recently developed A2 adenosine receptor agonist radioligand 2-[4-(2-[( 4-aminophenyl]methylcarbonyl)ethyl) phenyl]ethylamino-5'-N-ethylcarboxamido adenosine (125I-PAPA-APEC), we have demonstrated the presence of A2 adenosine receptors in this cell line. Saturation curves with 125I-PAPA-APEC indicated the Bmax and Kd values to be 0.21 pmol/mg of protein and 4.0 nM, respectively. In competition experiments, NECA was more potent at inhibiting 125I-PAPA-APEC binding than (R)-PIA, with their respective IC50 values being 5.6 and 351 nM. The photolabeled A2 adenosine receptor migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an Mr of 42,000. Finally, adenosine receptor agonists stimulated adenylate cyclase activity by approximately 2-3 fold with the following potency series: PAPA-APEC greater than or equal to NECA greater than (R)-PIA, indicative of their interaction at A2 receptors. These data represent the first demonstration of the presence of both A1 and A2 receptors in a single cell line, DDT1 MF-2 smooth muscle cells.
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PMID:Demonstration of both A1 and A2 adenosine receptors in DDT1 MF-2 smooth muscle cells. 230 50

We have studied the modulation of cyclic AMP (cAMP) accumulation by the human immunodeficiency virus type 1 (HIV 1) protein Tat in microglia and astrocyte cultures obtained from neonatal rat brain. Pretreatment of microglia with recombinant Tat resulted in a dose- and time-dependent decrease of cAMP accumulation induced by subsequent exposure to isoproterenol (1 microM). The inhibitory action of 100 ng/mL Tat approached 50% after 4 h of preincubation and reached a maximum of 70% after 24 h. The Tat-induced time- and dose-dependent decrease of cAMP accumulation was observed also when microglial cultures were stimulated with the adenylyl cyclase activator forskolin (100 microM). In both cases, Tat inhibitory action was 70% reverted by a specific monoclonal anti-Tat antibody, but was not prevented either by the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xantine (100 microM) or by a 16-h pretreatment of microglial cultures with the Gi protein inhibitor pertussis toxin (10 ng/mL). All these results suggested that the viral protein acts at a step of the cAMP transduction pathway other than receptors, G proteins and phosphodiesterases. The target of Tat appeared to be adenylyl cyclase, whose activity was markedly reduced (up to 60%) in membranes prepared from Tat-treated microglial cells, both in basal conditions and after stimulation with isoproterenol and forskolin. The inability of the competitive inhibitor of nitric oxide synthase N(G)-monometyl- L-arginine (20 and 200 microM) to revert Tat action on forskolin-induced cAMP accumulation, and of two potent nitric oxide donors, PAPA and DETA (0.1-2 m M), to alter forskolin-induced cAMP accumulation, excluded an involvement of nitric oxide in Tat-induced adenylyl cyclase inhibition. On the contrary, two inhibitors of nuclear factor kappaB activation, N-tosyl-( L)-phenylalanine chloromethyl ketone (10 microM) and SN50 (25 microM), markedly prevented the reduction of forskolin-evoked cAMP accumulation by Tat, suggesting a possible role for this nuclear transcriptional factor in the regulation of adenylyl cyclase by Tat in microglia. This assumption was strengthened by the ability of lipopolysaccharide (100 ng/mL, 4 h) to mimic the inhibitory effect of the viral protein. Conversely, astrocyte cAMP accumulation was unaffected by the viral protein, as tested at various concentrations and time points. Finally, Tat inhibition of microglial adenylyl cyclase was not due to non-specific cytotoxicity. As cAMP has been reported to exert a neuroprotective role in several in vivo and in vitro models of brain pathologies, and microglia is believed to mediate Tat-induced neurotoxicity, these results suggest that the ability of Tat to inhibit cAMP synthesis in microglia may contribute to neuronal degeneration and cell death associated with HIV infection.
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PMID:Human immunodeficiency virus type 1 Tat protein decreases cyclic AMP synthesis in rat microglia cultures. 1129 2