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)

Parameters of ligand binding, stimulation of low-Km GTPase, and inhibition of adenylate cyclase were determined in intact human neuroblastoma SH-SY5Y cells and in their isolated membranes, both suspended in identical physiological buffer medium. In cells, the mu-selective opioid agonist [3H]Tyr-D-Ala-Gly(Me)Phe-Gly-ol ([3H]DAMGO) bound to two populations of sites with KD values of 3.9 and 160 nM, with less than 10% of the sites in the high-affinity state. Both sites were also detected at 4 degrees C and were displaced by various opioids, including quaternary naltrexone. The opioid antagonist [3H]naltrexone bound to a single population of sites, and in cells treated with pertussis toxin the biphasic displacement of [3H]naltrexone by DAMGO became monophasic with only low-affinity binding present. The toxin specifically reduced high-affinity agonist binding but had no effect on the binding of [3H]naltrexone. In isolated membranes, both agonist and antagonist bound to a single population of receptor sites with affinities similar to that of the high-affinity binding component in cells. Addition of GTP to membranes reduced the Bmax for [3H]DAMGO by 87% and induced a linear ligand binding component; a low-affinity binding site, however, could not be saturated. Compared with results obtained with membranes suspended in Tris buffer, agonist binding, including both receptor density and affinity, in the physiological medium was attenuated. The results suggest that high-affinity opioid agonist binding represents the ligand-receptor-guanine nucleotide binding protein (G protein) complex present in cells at low density due to modulation by endogenous GTP.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Opioid signal transduction in intact and fragmented SH-SY5Y neural cells. 156 Feb 22

Alterations in brain opioid binding and opioid pharmacodynamics following chronic (8-day) naltrexone (NTX) treatment were determined in pertussis toxin (PTX)-treated mice. Intrathecal (IT) and intracerebroventricular (ICV) PTX produced a time-dependent, long-lasting inhibition of morphine (SC) analgesia without modifying basal nociception. Inhibition was maximal 16 days following PTX treatment, and was still observed at 40 days. Relative to placebo controls, NTX treatment produced supersensitivity to morphine analgesia in all control mice and in mice pretreated with PTX 1 day before NTX. Supersensitivity was not observed in 7-day PTX-pretreated mice. [3H][D-Ala2-D-Leu5]enkephalin ([3H]DADLE) and [3H][D-Ala2-MePhe4-Gly(ol)5]enkephalin ([3H]DAMGO) binding sites were increased by NTX treatment in saline- and PTX-pretreated groups. KDs were unchanged. These results indicate that PTX does not alter opioid antagonist-induced receptor upregulation. However, PTX treatment can diminish morphine potency in upregulated and control mice. Therefore, opioid analgesia in control and upregulated mice appears to be mediated by receptors linked to a common PTX-sensitive G-protein. Furthermore, in 7-day PTX-pretreated mice, NTX increased binding sites without altering morphine potency, which suggests that new binding sites can appear without being functionally coupled.
 ...
PMID:Dissociation of opioid receptor upregulation and functional supersensitivity. 165 19

There is accumulating evidence that pertussis toxin-sensitive G proteins are associated with the transduction of opioid-mediated antinociception in mammals. The present study examined the effects of hemocel injections of pertussis toxin (0.10 microgram) on the day-night rhythm of nociception and mu and kappa opioid-mediated antinociception in a mollusc, the land snail, Cepaea nemoralis. Five days after treatment, pertussis toxin significantly reduced the naloxone-sensitive, opioid-mediated nocturnal peak in the day-night rhythm of nociception [as measured by the latency of response to a thermal (40 degrees C) stimulus] in Cepaea, without affecting the daytime response latency. Pertussis toxin also significantly decreased the antinociceptive effects of the mu agonist, DAMGO, and blocked those of the kappa opioid agonist, U-69,593. These results suggest that G protein substrates of pertussis toxin are associated with the transduction of opioid-mediated nociception and antinociception in the snail, Cepaea.
 ...
PMID:Pertussis toxin reduces the day-night rhythm of nociception and mu and kappa opioid peptide-mediated antinociception in the snail, Cepaea nemoralis. 166 49

The effects of prolonged morphine exposure on the mu opioid receptor in 7315c pituitary tumor cell membranes have been examined. Since a low concentration of naloxone reversed the inhibition of forskolin-stimulated adenylyl cyclase induced by the mu-selective agonist, Tyr-D-Ala-Gly-MePhe-Gly-ol (DAGO), and by high concentrations of [D-Pen2-D-Pen5]enkephalin (DPDPE), we suggest that these cells contain a homogeneous population of mu opioid receptors coupled to adenylyl cyclase via a guanyl nucleotide-binding protein. Studies measuring the ability of [D-Ala2-D-Leu5]enkephalin (DADLE), an opioid agonist, to inhibit adenylyl cyclase in cells that had been exposed to 100 microM morphine for varying periods of time, indicated that the agonist no longer inhibited enzyme activity after 5 hr of morphine exposure. Measurements of 3H-antagonist binding in membranes from cells exposed to morphine demonstrated a decreased receptor density after 24 hr of 100 microM morphine exposure with no change in the antagonist affinity. Computer analysis indicated a 20% decrease in the number of mu receptors labeled after 24 hr of morphine exposure and a 60% decrease after 72 hr of exposure. Computer analysis of agonist competition against 3H-antagonist binding confirmed the existence of one binding site with an affinity intermediate between the high and low apparent affinity states observed in membranes from untreated cells. Addition of 10 microM GTP gamma S did not affect the agonist affinity or receptor density in membranes from morphine-treated cells, suggesting that the receptors were uncoupled from G proteins, as observed in 7315c cell membranes that have been treated with pertussis toxin. Thus chronic morphine treatment induced a rapid loss of opioid mu receptor-mediated inhibition of adenylyl cyclase (desensitization), and a more slowly developing reduction in receptor number. The desensitization was accompanied by a loss of guanyl nucleotide regulation of agonist affinity. These findings are comparable to results reported for the delta opioid receptor and the beta-adrenergic receptor upon prolonged agonist exposure.
 ...
PMID:Effects of chronic morphine exposure on opioid inhibition of adenylyl cyclase in 7315c cell membranes: a useful model for the study of tolerance at mu opioid receptors. 283 51

Incubation of SH-SY5Y neural cells with mycophenolic acid (MPA), an inhibitor of inosine monophosphate dehydrogenase (the key enzyme in purine nucleotide biosynthesis), reduced the cellular content of GTP by 94% relative to its concentration in control cells (43 nmol/mg protein) without altering the level of GDP. Although in GTP-depleted intact cells the receptor binding parameters (Kd and Bmax) of the opioid antagonist [3H]naltrexone were unchanged from those in untreated cells, the binding affinity of the mu-selective opioid agonist [3H]Tyr-D-Ala-Gly-(Me)- Phe-Gly-ol ([3H]DAMGO) was enhanced 2-fold. Furthermore, the kinetics of ligand/receptor interaction revealed that in the nucleotide-depleted cells, the dissociation rate constant for [3H]DAMGO was reduced by 44%. Initial exposure of SH-SY5Y cells to pertussis toxin reduced high-affinity ligand binding by 95% and abolished the effect of MPA treatment. Renewed incubation of the GTP-depleted cells with guanosine restored the original GTP levels and agonist binding. Neither MPA nor guanosine treatment changed the Bmax of [3H]DAMGO binding. Forskolin- and prostaglandin E1-stimulated adenylyl cyclase activities were decreased significantly in GTP-depleted cells. DAMGO and [D-Pen2,D-Pen5]enkephalin inhibitions of adenylyl cyclase were also affected with MPA treatment. Maximal inhibition of forskolin-stimulated adenylyl cyclase activity by both of the agonists was reduced, whereas MPA caused a 2-fold reduction in potency for DAMGO. The results show that reduction in endogenous GTP levels leads to noticeable changes in agonist, receptor, and G protein interactions, as measured by agonist binding, and to subsequent diminution of the signal transduction, as reflected by the cAMP levels.
 ...
PMID:Reversible modulation of opioid receptor binding in intact neural cells by endogenous guanosine triphosphate. 747 95

Intracerebroventricular (i.c.v.) administration of immune sera raised against Gi2 alpha subunits to mice, significantly reduced the supraspinal antinociceptive effect of opioids when evaluated 24 h later in the tail-flick test. Antisera directed against Gi1 alpha subunits did not modify this opioid activity. In mice injected with sera anti-Gx/z alpha, the mu-preferential agonists, DAMGO and morphine, and the endogenous mu/delta opioid peptide beta-endorphin-(1-31) displayed a reduced antinociceptive activity, whereas, the potency of the delta-selective agonists DPDPE and [D-Ala2]Deltorphin II, was not altered. This reduction was present for 3 to 7 days and returned to the control values after 10 days. Anti-Gi2 alpha and anti-Gx/z alpha, but not anti-Gi1 alpha, reduced the specific binding of [3H]DAMGO to the opioid receptor in PAG. These results suggest the ability of the mu receptor to interact in vivo with different classes of G transducer proteins (Gx/z/Gi2) to produce an effect. This work also indicates a functional role of the pertussis toxin insensitive Gx/z protein, on the mu-mediated (but not delta-mediated) supraspinal antinociception in mice.
 ...
PMID:Gx/z and Gi2 transducer proteins on mu/delta opioid-mediated supraspinal antinociception. 790 22

Total opioid binding in the human neuroblastoma cell line BE(2)-C has a density similar to that found in brain, with a Bmax value of 383 +/- 60 fmol/mg protein and a KD of 0.4 +/- 0.07 nM for the nonselective opioid antagonist 3H-diprenorphine. Selective assays reveal a binding distribution of mu (38%), delta (16%) and kappa 3 (43%) opioid receptors. There is no observable kappa 1 or kappa 2 binding. The sum of the Bmax values in the selective binding assays (370 +/- 39 fmol/mg protein) approximates closely that observed with 3H-diprenorphine, suggesting that mu, delta and kappa 3 sites account for most of the binding. The binding selectivities of various opiates and opioid peptides in the BE(2)-C cells are similar to those in rat brain. Delta and mu binding are defined easily by traditional selective ligands. The binding profiles also distinguish clearly mu from kappa 3 binding. The selective mu ligand DAMGO competes with mu binding over 35-fold more potently than kappa 3 binding, whereas morphine shows a 10-fold selectivity. Functionally, selective mu, delta and kappa 3 agonists inhibit forskolin-stimulated cAMP accumulation through distinct receptor mechanisms that are pertussis toxin-sensitive. In addition to demonstrating that BE(2)-C cells provide a useful model system for studying mu, kappa 3 and delta receptors, these studies confirm that kappa 3 receptors represent a pharmacologically distinct receptor class in this cell line.
 ...
PMID:Biochemical and pharmacological characterization of mu, delta and kappa 3 opioid receptors expressed in BE(2)-C neuroblastoma cells. 793 77

Both mu and delta opioid receptors are expressed in undifferentiated human neuroblastoma SHSY5Y cells and are negatively coupled to adenylate cyclase. The ability of various mu opioid, delta opioid and alpha-2 adrenergic agonists to inhibit acutely forskolin-stimulated adenylate cyclase activity in undifferentiated SHSY5Y cells after chronic administration with the selective mu opioid agonist [N-MePhe3,D-Pro4]morphiceptin (PLO17) or delta opioid agonist, [D-Pen2,D-Pen5]enkephalin (DPDPE) was assessed. In control cells, both PLO17 and DPDPE inhibited cyclic AMP (cAMP) formation with equal maximal inhibition, i.e., 60 +/- 3 and 66 +/- 2%, having IC50 values of 51.1 +/- 1.3 and 3.7 +/- 1.0 nM, respectively. The inhibition of intracellular cAMP formation by both agonists could be blocked by pertussis toxin pretreatment. After 24 hr of chronic administration of PLO17 (50 nM to 10 microM), a concentration-dependent loss of the ability of mu opioid agonists PLO17 and DAMGO, but not the delta opioid agonists DPDPE, nor alpha-2 adrenergic agonist UK-14304 (5-Bromo-N-(4,5,-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine) to inhibit adenylate cyclase activity was observed. In contrast, chronic administration of DPDPE (0.1 nM to 0.3 microM) resulted in a concentration-dependent reduction in the inhibition of cAMP formation produced by delta opioid agonists DPDPE and DSLET, but not mu opioid, nor alpha-2 adrenergic agonists tested. The observed homologous desensitization was also time-dependent. In addition, antagonist-induced increases in adenylate cyclase activity were observed only after chronic PLO17 administration.2+ Finally, chronic pretreatment of cells with PLO17 (10 microM) resulted in a significant decrease in mu opioid, but not delta opioid receptor, binding, whereas treatment with DPDPE (0.3 microM) resulted in a significant decrease in delta opioid, but not mu opioid receptor binding. Therefore, undifferentiated SHSY5Y cells may provide an excellent model system to study not only the signal transduction mechanisms of mu and/or delta opioid receptors, but also the cellular adaptations of specific opioid receptors.
 ...
PMID:Mu and delta opioid receptor desensitization in undifferentiated human neuroblastoma SHSY5Y cells. 803 14

1. In this study we have investigated delta and mu opioid receptor-mediated elevation of intracellular Ca2+ concentration ([Ca2+]i) in the human neuroblastoma cell line, SH-SY5Y. 2. The Ca(2+)-sensitive dye, fura-2, was used to measure [Ca2+]i in confluent monolayers of SH-SY5Y cells. Neither the delta-opioid agonist, DPDPE ([D-Pen2,5]-enkephalin) nor the mu-opioid agonist, DAMGO (Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol enkephalin) elevated [Ca2+]i when applied alone. However, when either DPDPE or DAMGO was applied in the presence of the cholinoceptor agonist, carbachol (100 nM-1 mM) they evoked an elevation of [Ca2+]i above that caused by carbachol alone. 3. In the presence of 1 microM or 100 microM carbachol, DPDPE elevated [Ca2+]i with an EC50 of 10 nM. The elevation of [Ca2+]i was independent of the concentration of carbachol. The EC50 for DAMGO elevating [Ca2+]i in the presence of 1 microM and 100 microM carbachol was 270 nM and 145 nM respectively. 4. The delta-receptor antagonist, naltrindole (30 nM), blocked the elevations of [Ca2+]i by DPDPE (100 nM) without affecting those caused by DAMGO while the mu-receptor antagonist, CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Pen-Thr-NH2) (100 nM-1 microM) blocked the elevations of [Ca2+]i caused by DAMGO (1 microM) without affecting those caused by DPDPE. 5. Block of carbachol activation of muscarinic receptors with atropine (10 microM) abolished the elevation of [Ca2+]i by the opioids. The nicotinic receptor antagonist, mecamylamine (10 microM), did not affect the elevations of [Ca2+]i caused by opioids in the presence of carbachol. 6. Muscarinic receptor activation, not a rise in [Ca2+]i, was required to reveal the opioid response. The Ca2+ channel activator, maitotoxin (3 ng ml-1), also elevated [Ca2+]i but subsequent application of opioid in the presence of maitotoxin caused no further changes in [Ca2+]i. 7. The elevations of [Ca2+]i by DPDPE and DAMGO were abolished by pretreatment of the cells with pertussis toxin (200 ng ml-1, 16 h). This treatment did not significantly affect the response of the cells to carbachol. 8. The opioids appeared to elevate [Ca2+]i by mobilizing Ca2+ from intracellular stores. Both DPDPE and DAMGO continued to elevate [Ca2+]i when applied in nominally Ca(2+)-free external buffer or when applied in a buffer containing a cocktail of Ca2+ entry inhibitors. Thapsigargin (100 nM), an agent which discharges intracellular Ca2+ stores, also blocked the opioid elevations of [Ca2+]i. 9. delta and mu Opioids did not appear to mobilize intracellular Ca2+ by modulating the activity of protein kinases. The application of H-89 (10 microM), an inhibitor of protein kinase A, H-7 (100 microM), an inhibitor of protein kinase C, protein kinase A and cyclic GMP-dependent protein kinase, or Bis I, an inhibitor of protein kinase C, did not alter the opioid mobilization of [Ca2+]i. 10. Thus, in SH-SY5Y cells, opioids can mobilize Ca2+ from intracellular stores but they require ongoing muscarinic receptor activation. Opioids do not elevate [Ca2+]i when applied alone.
 ...
PMID:delta- and mu-opioid receptor mobilization of intracellular calcium in SH-SY5Y human neuroblastoma cells. 878 87

In C6 glioma cells stably expressing a homogeneous population of the cloned rat mu opioid receptor, the binding affinities of opioid agonists and subsequent activation of G protein were examined. Opioid receptor number in membranes of these cells was high (10-30 pmol/mg protein [3H]diprenorphine binding sites). Opioids were found to bind to the receptor with high affinity [Tyr-D-Ala-Gly-(Me)Phe-Gly-ol (DAMGO) 0.23 nM; sufentanil 0.034 nM; morphine 0.16 nM]. Activation of G protein by opioid agonists was examined by measuring the stimulation of guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTP gamma S) binding. Sufentanil increased [35S]GTP gamma S binding by 326% with an EC50 value of 2.39 nM. Agonist stimulation of [35S]GTP gamma S binding was stereoselective, naltrexone-reversible, and pertussis toxin-sensitive. The "intrinsic activity" of opioids at the mu receptor was reflected by the magnitude of agonist-mediated activation of G protein. The rank order of the stimulation of [35S]GTP gamma S binding was etonitazene = sufentanil = DAMGO = PLO17 = fentanyl > morphine > profadol > meperidine > butorphanol = nalbuphine = pentazocine > cyclazocine = nalorphine > levallorphan > naltrexone. High affinity binding of ligands to the mu opioid receptor was reduced by the addition of sodium and guanosine diphosphate at concentrations used in the [35S]GTP gamma S binding assay. Ligand affinity was reduced in a manner correlating with "intrinsic activity". DAMGO, 1229-fold, nalbuphine 35-fold, naltrexone, 3-fold. The results presented show that the stable expression of the rat mu opioid receptor in C6 cells provides an effective tool to examine opioid receptor signal transduction mechanisms and evaluate the activity of novel opioids at the mu receptor.
 ...
PMID:Characterization of opioid agonist efficacy in a C6 glioma cell line expressing the mu opioid receptor. 881 94


1 2 3 4 5 6 7 Next >>