Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The highly conserved aspartate residue in the second transmembrane domain of G protein-coupled receptors is present in position 113 in the type 1 neurotensin receptor (NTR1) but is replaced by an Ala residue in position 79 in the type 2 neurotensin receptor (NTR2). NTR1 couples to Galphaq to stimulate phospholipase C and its binding affinity for neurotensin is decreased by sodium ions and GTP analogs. By contrast, NTR2 does not seem to couple to any G protein in eukaryotic cells, and its binding of neurotensin is insensitive to sodium and GTP analogs. By using site-directed mutagenesis, we substituted Asp113 of the NTR1 by alanine and the homologous residue Ala79 of NTR2 by aspartate. Both mutant receptors display similar affinity for neurotensin as compared with their respective wild type. We demonstrate that the presence of the Asp residue determines by itself the occurrence of the sodium effect on neurotensin affinity for both wild-type and mutated NTR1 and -2. The introduction of an Asp in the second transmembrane domain of NTR2 is not enough to restore a functional coupling to G proteins. In contrast, replacement of Asp113 by Ala residue in NTR1 strongly decreases its ability to activate inositol turnover, indicating that the functionally active conformation of NTR1 is maintained by interaction of sodium ions with aspartate 113.
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PMID:Pivotal role of an aspartate residue in sodium sensitivity and coupling to G proteins of neurotensin receptors. 992 10

Three members of the ghrelin receptor family were characterized in parallel: the ghrelin receptor, the neurotensin receptor 2 and the orphan receptor GPR39. In transiently transfected COS-7 and human embryonic kidney 293 cells, all three receptors displayed a high degree of ligand-independent signaling activity. The structurally homologous motilin receptor served as a constitutively silent control; upon agonist stimulation, however, it signaled with a similar efficacy to the three related receptors. The constitutive activity of the ghrelin receptor and of neurotensin receptor 2 through the G(q), phospholipase C pathway was approximately 50% of their maximal capacity as determined through inositol phosphate accumulation. These two receptors also showed very high constitutive activity in activation of cAMP response element-driven transcription. GPR39 displayed a clear but lower degree of constitutive activity through the inositol phosphate and cAMP response element pathways. In contrast, GPR39 signaled with the highest constitutive activity in respect of activation of serum response element-dependent transcription, in part, possibly, through G(12/13) and Rho kinase. Antibody feeding experiments demonstrated that the epitope-tagged ghrelin receptor was constitutively internalized but could be trapped at the cell surface by an inverse agonist, whereas GPR39 remained at the cell surface. Mutational analysis showed that the constitutive activity of both the ghrelin receptor and GPR39 could systematically be tuned up and down depending on the size and hydrophobicity of the side chain in position VI:16 in the context of an aromatic residue at VII:09 and a large hydrophobic residue at VII:06. It is concluded that the three ghrelin-like receptors display an unusually high degree of constitutive activity, the structural basis for which is determined by an aromatic cluster on the inner face of the extracellular ends of TMs VI and VII.
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PMID:Common structural basis for constitutive activity of the ghrelin receptor family. 1538 39

G-protein-coupled receptors (GPCR) are now regarded as being able to acquire heterodimer conformations affecting their pharmacology, signaling and trafficking. In co-immunoprecipitation studies using differentially epitope-tagged receptors, we herein provide direct evidence for heterodimerization of human neurotensin type 1 receptor (hNTR1) and type 2 receptor (hNTR2). Using chimeric constructs, we also identified the hNTR2 transmembrane 2 (TM2) to TM4 region as crucial for the formation of the dimerization interface. At the functional level, we demonstrated that the co-expression of hNTR2 suppressed hNTR1-mediated adenylate cyclase/cAMP and phospholipase C activation. Finally, confocal microscopy revealed that whereas tagged hNTR1 expressed alone were localized to the plasma membrane, co-expression of hNTR2 caused the retention of hNTR1 in sub-cellular compartments, indicating that heterodimerization with hNTR2 interferes with the proper recruitment of hNTR1 to the plasma membrane. Overall, this study proposes a novel function of NTR2 in the regulation of NTR1 activity.
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PMID:Intermolecular cross-talk between NTR1 and NTR2 neurotensin receptor promotes intracellular sequestration and functional inhibition of NTR1 receptors. 1996 61

This study assessed the expression, distribution and function of neurotensin (NTs) and two main neurotensin receptors (NTSR), NTSR1 and NTSR2 in normal rat urinary bladders. NTs is primarily located in the suburothelium and the interstitium of smooth muscle bundles. The NTSR1 and NTSR2 receptor subtypes are found to co-localize with smooth muscle cells (SMCs). NTs not only can directly act on bladder SMCs to induce intracellular calcium mobilization by activating the phospholipase C/inositol triphosphate (PLC/IP3) pathway, promoting extracellular calcium influx through a non-selective cation channels, but may be also involved in the modulation of the cholinergic system. Nowadays, the selective antimuscarinic drugs (solifenacin) and the selective beta 3-adrenergic agonist (mirabegron) are used as the first-line pharmacotherapy for overactive bladder (OAB), but without satisfactory treatment benefits in some patients. This study provided evidence suggesting that bladder NTs may play an important role in the regulation of micturition. Further research is needed to investigate the effects of NTs on bladder contractility and the underlying mechanism, which might reveal that the administration of NTSR antagonists can potentially relieve the symptoms of OAB by coordination with antimuscarinic pharmacotherapy.
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PMID:The actions of neurotensin in rat bladder detrusor contractility. 2605 52