Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mu opiate receptor is a principal brain site for activities of morphine, other opiate drugs, and opioid peptides in modulating pain and altering mood. Recent cloning of cDNAs encoding rat and human mu receptors reveals charged amino acid residues within putative transmembrane domains (TMs) II, III, and VI, a substantial N-terminal extracellular domain, and a C-terminal intracellular domain. Deletion of 64 N-terminal amino acids produced little effect on receptor function (Wang, J.B., Imai, Y., Eppler, C.M., Gregor, P., Spivak, C.E., and Uhl, G.R. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 10230-10234). Further deletion of 33 C-terminal amino acids yielded a receptor at which morphine, but not the substituted enkephalin DAMGO ([D-Ala2,MePhe4,Glyol5]enkephalin), inhibited adenylate cyclase. Alanine substitution for each charged TM residue in the N-terminally deleted receptor reduced affinities for morphine, DAMGO, and the opiate antagonist naloxone. Replacement of TM II Asp114 with asparagine or glutamic acid increased mu receptor affinity for naloxone. TM II and TM III glutamic acid substitutions for Asp114 and Asp147 reduced agonist binding affinities but allowed full inhibition of adenylate cyclase at high agonist concentrations. TM VI histidine substitution with alanine yielded a receptor that produced almost twice the cyclase inhibition displayed by the wild type receptor in parallel transient expression assays. These findings underscore the importance of charged residues in TM II, III, and VI for different receptor functions and the modest involvement of extensive portions of N- and C-terminal receptor domains in these processes.
...
PMID:-mu opiate receptor. Charged transmembrane domain amino acids are critical for agonist recognition and intrinsic activity. 805 Nov 54

A human neuroblastoma cell line, SK-N-BE, was shown to express a substantial amount of opioid receptors (200-300 fmol/mg of protein). A ligand binding profile of these receptors revealed that they could belong to two distinct subtypes of delta-opioid receptors. Results from sucrose-gradient sedimentation experiments were compared with similar data obtained with the mu-opioid receptor of the rabbit cerebellum and the delta-opioid receptor of the hybrid NG108-15 cell line and have shown that the opioid receptor of the SK-N-BE cell line behaved hydrodynamically as an intermediate between mu- and delta-opioid receptors. Taken together, pharmacological and hydrodynamic studies suggest that the opioid receptors present in the SK-N-BE cell membranes could belong to two delta-opioid receptor subtypes interacting allosterically. Functional experiments suggest that at least one of these subtypes of delta-opioid receptor is negatively coupled to the adenylate cyclase via a Gi protein and that the opiate receptors of the SK-N-BE neuroblastoma cell line undergo a rapid down-regulation when preincubated in the presence of the high-affinity opioid, etorphine.
...
PMID:SK-N-BE: a human neuroblastoma cell line containing two subtypes of delta-opioid receptors. 811 11

Western blot analysis, using subtype-specific anti-G protein antibodies, revealed the presence of the following G protein subunits in human neuroblastoma SH-SY5Y cells: Gs alpha, Gi alpha 1, Gi alpha 2, Go alpha, Gz alpha, and G beta. Differentiation of the cells by all-trans-retinoic acid (RA) treatment (10 mumol/L; 6 days) caused substantial alterations in the abundance of distinct G protein subunits. Concomitant with an enhanced expression of mu-opioid binding sites, the levels of the inhibitory G proteins Gi alpha 1 and Gi alpha 2 were found to be significantly increased. This coordinate up-regulation is accompanied by functional changes in mu-opioid receptor-stimulated low-Km GTPase, mu-receptor-mediated adenylate cyclase inhibition, and receptor-independent guanosine 5'-(beta gamma-imido)triphosphate [Gpp(NH)p; 10 nmol/L]-mediated attenuation of adenylate cyclase activity. In contrast, increased levels of inhibitory G proteins had no effect on muscarinic cholinergic receptor-mediated adenylate cyclase inhibition. With respect to stimulatory receptor systems, a reciprocal regulation was observed for prostaglandin E1 (PGE1) receptors and Gs alpha, the G protein subunit activating adenylate cyclase. RA treatment of SH-SY5Y cells increases both the number of PGE1 binding sites and PGE1-stimulated adenylate cyclase activity, but significantly reduced amounts of Gs alpha were found. This down-regulation is paralleled by a decrease in the stimulatory activity of Gs alpha as assessed in S49 cyc- reconstitution assays.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Retinoic acid-induced differentiation of human neuroblastoma SH-SY5Y cells is associated with changes in the abundance of G proteins. 813 63

Tolerance to chronic morphine treatment was studied in adult rabbits and modifications in the number and the state of coupling of the mu-opioid receptors were investigated in the cerebellum. Tolerance was induced by the subcutaneous injection of progressively increasing doses of morphine (5-100 mg/kg/injection) over 6 days and its occurrence was controlled by a nociceptive test: electrical stimulation of the dental pulp. At the end of the treatment, the rabbits were tolerant to the analgesic effects of morphine and the tolerance phenomenon correlated well with a significant decrease in the adenylate cyclase inhibition (approximately 60%). The functional uncoupling between the enzyme and the mu-opioid receptor was accompanied neither by a decrease in the number of high affinity receptors measured by equilibrium binding techniques (Kd = 0.19 +/- 0.03 in control vs. 0.11 +/- 0.04 nM in tolerant animals; Bmax = 322 +/- 62 vs. 362 +/- 58 fmol/mg of protein), nor by a modification of the physical coupling between the receptor and its G-protein. It can be concluded that desensitization, under our experimental conditions, can be clearly distinguished from down-regulation.
...
PMID:Chronic morphine induces tolerance and desensitization of mu-opioid receptor but not down-regulation in rabbit. 815 68

The apparent affinities of endogenous opioid peptides for noncompetitively interacting mu and delta receptors, inhibitorily linked to dopamine (DA) D-1 receptor-stimulated adenylate cyclase, were investigated in superfused rat striatal slices exposed to 40 microM DA in the presence of 10 microM of the selective D-2 receptor antagonist (-)sulpiride. In the presence of peptidase inhibitors, a comparison was made with the apparent affinities of opioid peptides toward independent presynaptic opioid receptors in brain slices. beta-Endorphin had an about 100-fold higher apparent affinity (EC50: 1 nM) toward presynaptic mu-opioid receptors, mediating inhibition of the electrically evoked neocortical [3H]norepinephrine release, than for the striatal adenylate cyclase-coupled mu receptors. In contrast, the kappa-opioid receptor agonist dynorphin A1-13 displayed a similar apparent affinity (EC50: 0.1 microM) toward these functionally different mu receptors. Both Leu- and Met-enkephalin showed only a 3-fold higher apparent affinity (EC50: 30 nM) for presynaptic delta-opioid receptors, mediating inhibition of striatal [14C]acetylcholine release, than for presynaptic mu receptors. However, whereas Leu-enkephalin had a similar apparent affinity for presynaptic and adenylate cyclase-coupled delta receptors, Met-enkephalin displayed a 30-fold selectivity toward the latter receptors. Studying the inhibitory effect of Met-enkephalin on striatal adenylate cyclase stimulated by endogenously released (amphetamine-induced) DA, its very high affinity appeared to be inversely related to the activation of inhibitory DA D-2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Mu- and delta-opioid receptors inhibitorily linked to dopamine-sensitive adenylate cyclase in rat striatum display a selectivity profile toward endogenous opioid peptides different from that of presynaptic mu, delta and kappa receptors. 822 47

By screening a rat brain cDNA library using a cloned mu opioid receptor cDNA as probe, a clone was identified that is very similar to both the mu and delta opioid receptor sequences. Transient expression of this clone in COS-7 cells showed that it encodes a kappa opioid receptor, designated KOR-1, which is capable of high-affinity binding to kappa-selective ligands. Treatment of transfected cell membranes with bremazocine, a kappa-selective agonist, resulted in a 53% decrease in adenylate cyclase activity, indicating that this kappa opioid receptor displays inhibitory coupling to adenylate cyclase. Thus, one member from each of the three opioid receptor types, mu, kappa and delta, has been molecularly cloned. Analysis of sequence similarities among these opioid receptors, as well as between opioid receptors and other G-protein-coupled receptors, revealed regions of sequence conservation that may underlie the ligand-binding and functional specificities of opioid receptors.
...
PMID:Molecular cloning of a rat kappa opioid receptor reveals sequence similarities to the mu and delta opioid receptors. 824 Feb 67

We report a novel agonist-induced change in delta-opioid receptor binding properties in NG108-15 cells. Pretreatment of these cells with opioid agonists substantially diminishes the binding of peptide agonists and a peptide antagonist to opioid receptors in intact cells or membrane preparations. However, similar agonist-induced changes in the binding of opiate alkaloid agonists and antagonists were not detected. The change in opioid peptide binding occurs rapidly at 37 degrees (t1/2 approximately 10 min) but is not induced by agonist treatment at 4 degrees. Because of its lability at 37 degrees, the binding change is only detected when equilibrium binding assays are performed at 4 degrees. Both alkaloid and peptide agonists induce the binding change in a dose-dependent manner, with an ED50 for etorphine of approximately 10 nM. The induction of the binding change is completely blocked by the opiate antagonist naloxone. Stimulation of muscarinic receptors (which, like opioid receptors, inhibit adenylate cyclase in these cells) does not induce or block the binding change. These data reveal the operation of a homologous regulation mechanism that rapidly diminishes the interaction of delta-subtype opioid receptors with peptide ligands but does not detectably change the interaction of receptors with alkaloid ligands.
...
PMID:Agonist-induced state of the delta-opioid receptor that discriminates between opioid peptides and opiate alkaloids. 839 18

Using CHO cells stably transfected with rat mu-opioid receptor cDNA, we show that the mu-agonists morphine and [D-Ala2,N-methyl-Phe4,Gly-ol5]enkephalin are negatively coupled to adenylylcyclase and inhibit forskolin-stimulated cAMP accumulation. Chronic exposure of cells to morphine leads to the rapid development of tolerance. Withdrawal of morphine or [D-Ala2,N-methyl-Phe4,Gly-ol5]enkephalin following chronic treatment (by wash or addition of the antagonist naloxone) leads to an immediate increase in cyclase activity (supersensitization or overshoot), which is gradually reversed upon further incubation with naloxone. Phosphodiesterase inhibitors do not affect the overshoot, indicating that it results from cyclase stimulation rather than phosphodiesterase regulation. Morphine's potency to inhibit cAMP accumulation is the same before and after chronic treatment, suggesting that the apparent tolerance results from cyclase activation, rather than from receptor desensitization. The similar kinetics of induction of tolerance and overshoot support this idea. Both the overshoot and acute opioid-induced cyclase inhibition are blocked by naloxone and are pertussis toxin-sensitive, indicating that both phenomena are mediated by the mu-receptor and Gi/G(o) proteins. The supersensitization is cycloheximide-insensitive, indicating that it does not require newly synthesized proteins. This is supported by the rapid development of supersensitization. Taken together, these results show that mu-transfected cells can serve as a model for investigating molecular and cellular mechanisms underlying opiate drug addiction.
...
PMID:Adenylylcyclase supersensitization in mu-opioid receptor-transfected Chinese hamster ovary cells following chronic opioid treatment. 853 Mar 63

Prolongation of the action potential duration of dorsal root ganglion (DRG) neurons by low (nM) concentrations of opioids occurs through activation of excitatory opioid receptors that are positively coupled via Gs regulatory protein to adenylate cyclase. Previous results suggested GM1 ganglioside to have an essential role in regulating this excitatory response, but not the inhibitory (APD-shortening) response to higher (microM) opioid concentrations. Furthermore, it was proposed that synthesis of GM1 is upregulated by prolonged activation of excitatory opioid receptor functions. To explore this possibility we have utilized cultures of hybrid F11 cells to carry out closely correlated electrophysiological and biochemical analyses of the effects of chronic opioid treatment on a homogeneous population of clonal cells which express many functions characteristic of DRG neurons. We show that chronic opioid exposure of F11 cells does, in fact, result in elevated levels of GM1 as well as cyclic adenosine monophosphate (AMP), concomitant with the onset of opioid excitatory supersensitivity as manifested by naloxone-evoked decreases in voltage-dependent membrane K+ currents. Such elevation of GM1 would be expected to enhance the efficacy of excitatory opioid receptor activation of the Gs/adenylate cyclase/cyclic AMP system, thereby providing a positive feedback mechanism that may account for the remarkable supersensitivity of chronic opioid-treated neurons to the excitatory effects of opioid agonists as well as antagonists. These in vitro findings may provide novel insights into the mechanisms underlying naloxone-precipitated withdrawal syndromes and opioid-induced hyperalgesia after chronic opiate addiction in vivo.
...
PMID:Chronic opioid treatment of neuroblastoma x dorsal root ganglion neuron hybrid F11 cells results in elevated GM1 ganglioside and cyclic adenosine monophosphate levels and onset of naloxone-evoked decreases in membrane K+ currents. 856 36

Signal transduction cascades initiated by the neuronal kappa opioid receptor were studied following transfection of a neuronal (hippocampal) line, HN2, and the non-neural CHOs. Retinoic-acid mediated differentiation resulted in intense staining of the HN2 cells with a neurofilament protein antibody SMI 33 but not with an antibody to GFAP, thus establishing neuronal characteristics of the HN2 cell line. The kappa opioid receptor was stably expressed in the two cell lines by electroporation mediated transfer of a Cytomegalovirus-promoter driven construct, pCMV-kappa, harboring the kappa-opioid receptor cDNA. Positive clones (HN2 kappa 24 and CHO kappa 18) from both lines showed high expression of the kappa opioid receptor, as identified by [3H] U-69,593 binding to membranes prepared from HN2 kappa 24 and CHO kappa 18. Scatchard analysis revealed the presence of high affinity kappa opioid receptors in both engineered cell lines (KD=1.3 nM for HN2 kappa 24 and 2.1 nM for CHO kappa 18). Functional coupling to adenylate cyclase was displayed by 1 microM U-69,593 mediated inhibition (55-63%) of prostaglandin E1-stimulated intracellular cAMP levels. A major difference between the two clones was observed in functional coupling of the expressed kappa opioid receptor to phospholipases C (PL-C) and D (PL-D). U-69,593 (1 microM) treatment stimulated PL-C, but not PL-D, in HN2 kappa 24 cells, whereas PL-D, but not PL-C, was stimulated following such treatment of CHO kappa 18 cells. Our results using the model neuronal system, HN2 kappa 24, demonstrate cell-type specific, positive coupling of the kappa opioid receptor to the major Ca2+ mobilizing system, the PL-C cascade, which regulates neuronal firing.
...
PMID:Stable expression and heterologous coupling of the kappa opioid receptor in cell lines of neural and nonneural origin. 861 81


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---