Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In an attempt to determine the mechanism by which the tripeptide l-prolyl-l-leucyl-glycine amide (PLG, MIF-I) exerts its antiparkinsonian effect, the action of this substance on various postsynaptic components of striatal dopaminergic nerves was studied. It was shown that injection of rats with MIF-I (1 mg/kg, IPX5, 24 hr intervals) did not alter tyrosine hydroxylase, dopa decarboxylase, choline acetyltransferase and glutamic acid decarboxylase activities in the striatum under the conditions tested. The activities of adenylate cyclase, dopamine-stimulated adenylate cyclase, and guanylate cyclase were not altered in vitro by various concentrations of MIF-I (0.1 to 1000 micrometer), although VIP and neurotensin had some effect. Also the rate of uptake of 3H-dopamine by rat striatal synaptosomes was unchanged, as was the binding of 3H-dopamine and 3H-spiperone to beef caudate membranes. This series of studies indicates that MIF-I does not act directly on the striatal dopamine postsynaptic receptor under the conditions tested, although it is possible that MIF-I could act indirectly at this or another site in vivo by releasing or activating some other factor.
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PMID:MIF-I and postsynaptic receptor sites for dopamine. 3 65

Endothelial cells (ECs) from brain microvessels respond to exogenous nitric oxide (NO) donor molecules (N-ethoxycarbonyl-3-morpholinosydnonimine and sodium nitroprusside) with large (greater than 15-fold) increases in cyclic GMP (cGMP) levels. Comparable actions of sodium nitroprusside were observed in vascular smooth muscle cells and in neuroblastoma cells. Coculturing brain capillary ECs in the presence of N1E-115 neuroblastoma cells increased their cGMP levels fourfold. A further increase was observed in the presence of 50 nM neurotensin, although brain capillary ECs lack receptor sites for neurotensin. The neuroblastoma cell-dependent formation of cGMP was suppressed by 0.1 mM L-NG-monomethylarginine, indicating that NO, produced by N1E-115 cells in response to neurotensin, activated guanylate cyclase in brain capillary ECs. Similarly, culturing brain capillary ECs in the presence of aortic ECs increased their cGMP content in a manner that was amplified by bradykinin and that was inhibited by L-NG-monomethylarginine. Bradykinin had no action in pure cultures of brain capillary ECs. It is concluded that brain capillary ECs express high levels of guanylate cyclase activity that could be activated by exogenous NO donor molecules and by NO produced by neuroblastoma cells and by aortic ECs in response to specific agonists. Brain capillary ECs are thus potential target cells for brain-derived NO.
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PMID:Activation by nitric oxide of guanylate cyclase in endothelial cells from brain capillaries. 135 91

Rat neurotensin (NT) receptor (NTR) cDNA was subcloned into the pRC-CMV expression vector and transfected into 293 cells, and cellular clones that stably expressed the NTR were isolated and characterized. [3H]NT binding to membranes prepared from the NTR cDNA-transfected cells displayed specificity and saturability, with an apparent Kd of 1.25 nM and a Bmax of 43.4 pmol/mg of protein (approximately 3.5 x 10(6) binding sites/cell). NT stimulated an increase in [3H]inositol phosphate levels in the NTR-expressing cells up to 2500% of basal levels. The response was time and dose dependent, with an EC50 of 10.4 nM. NT also stimulated cAMP formation in these cells, with an EC50 of 27.0 nM. In addition, NT evoked an increase in the level of intracellular calcium. Approximately 60% of the calcium rise was attributable to the release of intracellular stores and 40% was attributable to calcium influx. Although NTR occupancy has been shown to stimulate cGMP formation in several brain preparations and cell lines, NT was unable to mediate cGMP synthesis in the NTR-expressing 293 cells. We found that 293 cells have guanylate cyclase activity but have undetectable levels of nitric oxide synthase (NOS) activity. Because it was possible that the production of nitric oxide is required as the mediator of NT-induced cGMP synthesis, we subcloned NOS cDNA into the pCEP4 expression vector and transiently expressed it in the NTR cells. We report that NT increased cGMP levels up to 375% of basal levels when NOS cDNA was coexpressed and that the increase was completely inhibited by the NOS inhibitor N omega-nitro-L-arginine. NT-induced cGMP accumulation was time and dose dependent, with an EC50 of 1.7 nM. To our knowledge, this is the first report of NT mediating cGMP formation with a cloned receptor and the first evidence that NT-induced cGMP accumulation requires the production of nitric oxide.
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PMID:The cloned neurotensin receptor mediates cyclic GMP formation when coexpressed with nitric oxide synthase cDNA. 752 Jan 23

Murine neuroblastoma clone N1E-115 cells possess neurotensin receptors that are coupled to polyphosphoinositide hydrolysis and cyclic guanosine 3',5'-monophosphate (cGMP) formation. These responses rapidly desensitize and these receptors rapidly down-regulate nearly completely in about 15 min. Although neurotensin is rapidly degraded by peptidases, in this study we show that at 37 degrees neurotensin (100 nM) in the absence of peptidase inhibitors caused this rapid desensitization and down-regulation (32 +/- 5 and 24 +/- 2% of control, respectively) of neurotensin receptors in N1E-115 cells. In addition, we demonstrated that this desensitization, resensitization, down-regulation and recovery of binding sites were temperature dependent. These data suggest that a certain degree of phospholipid fluidity or activity of some enzymes is required for these processes to occur. After addition of sodium nitroprusside or ionomycin to cells, cGMP increased in desensitized cells to the same degree as in control cells. Additionally, desensitization and down-regulation occurred in the absence of a change in the affinity of neurotensin for the remaining sites. These data suggest that desensitization is not caused by changes in nitric oxide synthesis, guanylyl cyclase activity or receptor affinity, but predominantly by a decrease in receptor number.
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PMID:Further characterization of neurotensin receptor desensitization and down-regulation in clone N1E-115 neuroblastoma cells. 839 Feb 62

Smooth muscle cells isolated from the gastric muscle layers of the guinea pig were used to determine whether neurotensin can inhibit the contractile response produced by 10(-6) M carbachol by exerting a direct action on muscle cells. In addition, the inhibitory effect of 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, and methylene blue, an inhibitor of guanylate cyclase, on the neurotensin-induced relaxation of gastric smooth muscle cells were examined. Neurotensin inhibited the contractile response produced by carbachol in a dose-dependent manner, with an IC50 value of 5 nM. 2',5'-Dideoxyadenosine did not have any significant effect on the neurotensin-induced relaxation. On the other hand, methylene blue significantly inhibited the relaxation produced by neurotensin. These results strongly suggest that the action of neurotensin is mediated by cyclic GMP.
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PMID:Direct inhibitory effect of neurotensin on isolated gastric smooth muscle cells of guinea pig via the cyclic GMP system. 839 31

The recently cloned new subtype of G protein-coupled neurotensin receptor (NTRL) was stably expressed in the HEK 293 cell line in order to investigate its binding and internalization properties. The expressed receptor exhibited the typical binding characteristics of the low affinity, levocabastine-sensitive binding site previously described in rat and mouse brain and was detected as a protein with an apparent MW of 45 kDa by photoaffinity labeling. Although intracellular modulation of adenylate cyclase, guanylate cyclase and phospholipase C was not detected after application of neurotensin or levocabastine on NTRL-transfected cells, this receptor was able to internalize iodinated neurotensin. The internalization process was followed by recycling of receptors to the cell membrane. By contrast, no recycling was observed with the high affinity neurotensin receptor (NTRH). The differential intracellular routing of NTRH and NTRL after internalization is most probably the consequence of their divergent carboxy-terminal sequences.
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PMID:Stable expression of the mouse levocabastine-sensitive neurotensin receptor in HEK 293 cell line: binding properties, photoaffinity labeling, and internalization mechanism. 948 Aug 52

Research is currently underway worldwide into the development of receptor-specific radiopharmaceuticals for the imaging and treatment of cancer. The successful clinical development of radiolabeled somatostatin analogs for imaging and treatment of cancers overexpressing somatostatin receptors has catalyzed further preclinical investigation of other radiolabeled peptides for molecular imaging and peptide-receptor radiotherapy, including such well-studied peptide vectors as cholecystokinin, neurotensin, bombesin and RGD peptides. Within this larger context, this article will focus on the current status of two more recent additions to the list of molecular imaging targets - guanylate cyclase C, a specific marker for colorectal cancer, and the urokinase plasminogen activator receptor, a cell-surface receptor overexpressed in diverse cancer types.
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PMID:Radiometallated peptides targeting guanylate cyclase C and the urokinase-type plasminogen activator receptor. 2079 77