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 family of serotonin 5-HT2 receptors stimulates the phospholipase C second messenger pathway via the alpha subunit of the Gq GTP-binding protein. Here, we show that agonist stimulation of the 5-HT2B receptor subtype stably expressed in the mouse fibroblast LMTK- cell line causes a rapid and transient activation of the proto-oncogene product p21ras as measured by an increase in GTP-bound Ras in response to serotonin. Furthermore, 5-HT2B receptor stimulation activates p42mapk/p44mapk (ERK2/ERK1) mitogen-activated protein kinases as assayed by phosphorylation of myelin basic protein. Antibodies against p21ras, Galphaq, -beta, or -gamma2 subunits of the GTP-binding protein inhibit MAP kinase-dependent phosphorylation. The MAP kinase activation is correlated with a stimulation of cell division by serotonin. In addition to this mitogenic action, transforming activity of serotonin is mediated by the 5-HT2B receptor since its expression in LMTK- cells is absolutely required for foci formation and for these foci to form tumors in nude mice. Finally, we detected expression of the 5-HT2B receptor in spontaneous human and Mastomys natalensis carcinoid tumors and, similar to the 5-HT2B receptor transfected cells, the Mastomys tumor cells are also responsive to serotonin with similar coupling to p21ras activation.
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PMID:Ras involvement in signal transduction by the serotonin 5-HT2B receptor. 862 13

Clinical disorders associated with increased serotonin [5-hydroxytryptamine (5-HT)] levels, such as carcinoid syndrome, and the use of serotonin agonists, such as fenfluoramine have been associated with a valvulopathy characterized by hyperplastic valvular and endocardial lesions with increased extracellular matrix. Furthermore, 5-HT has been demonstrated to up-regulate transforming growth factor (TGF)-beta in mesangial cells via G-protein signal transduction. We investigated the hypothesis that increased exposure of heart valve interstitial cells to 5-HT may result in increased TGF-beta1 expression and activity because of serotonin receptor-mediated signal transduction with activation of Galphaq, and subsequently up-regulation of phospholipase C. Thus, in the present study we performed a clinical-pathological investigation of retrieved carcinoid and normal valve cusps using immunohistochemical techniques to detect the presence of TGF-beta1 and other proteins associated with TGF-beta expression, including TGF-beta receptors I and II, latent TGF-beta-associated peptide (LAP), and alpha-smooth muscle actin. Carcinoid valve cusps demonstrated the unusual finding of widespread smooth muscle actin involving the interstitial cells in the periphery of carcinoid nodules; these same cells were also positive for LAP. Normal valve cusps were only focally positive for smooth muscle actin and LAP. In sheep aortic valve interstitial cell cultures 5-HT induced TGF-beta1 mRNA production and increased TGF-beta1 activity. 5-HT also increased collagen biosynthesis at the dosages studied. Furthermore, TGF-beta1 added to SAVIC cultures increased the production of sulfated glycan and hyaluronic acid. In addition, overexpression of Galphaq using an adenoviral expression vector for a constitutively active Galphaq mutant (Q209L-Galphaq) resulted in increased phospholipase C activity as well as up-regulation of TGF-beta expression and activity. These results strongly support the view that G-protein-related signal transduction is involved in 5-HT up-regulation of TGF-beta1. In conclusion, 5-HT-associated valve disease may be, in part, because of TGF-beta1 mechanisms.
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PMID:Serotonin mechanisms in heart valve disease I: serotonin-induced up-regulation of transforming growth factor-beta1 via G-protein signal transduction in aortic valve interstitial cells. 1246 27

Serotonin [5-hydroxytryptamine (5-HT)]-mediated cardiac valvular disease has been commonly observed in patients with carcinoid tumors. Previous research by others using reverse transcriptase-polymerase chain reaction demonstrated that aortic valve cells expressed predominantly 5-HT(2A/2B) receptors (5-HT(2A)R). Related investigations by our group using sheep aortic valve interstitial cell (SAVIC) cultures demonstrated that 5-HT both up-regulates transforming growth factor (TGF)-beta1 expression and activity, and also results in increased phospholipase C (PLC) activity. Thus, the present study investigated the hypothesis that the 5-HT signaling pathway in SAVICs involves 5-HT(2)Rs with associated G-protein signal transduction. The objectives were to functionally characterize in SAVIC cultures the native serotonin receptor subtypes using specific agonists and antagonists, and to delineate the serotonin-signaling pathway. 5-HT administration caused a marked stimulation of PLC activity. SAVIC studies of specific agents that target the 5-HT(2)R subtypes indicate that this response seemed to be mediated predominantly by 5-HT(2A)Rs. Furthermore, the sheep 5-HT(2A)R was identified by reverse transcriptase-polymerase chain reaction with sequence confirmation including comparisons to pig and human 5-HT(2A)R. Extracellular signal-regulated kinase (Erk 1/2) is a signaling molecule downstream from the 5-HT(2A)R. Both a protein kinase C inhibitor, GF109203X, and a Src inhibitor, PP1, attenuated 5-HT-stimulated Erk 1/2 activation. However, a 5-HT(2A)R antagonist, MDL 100907, inhibited 5-HT up-regulation of PLC and TGF-beta1, while having far less pronounced effects on Erk 1/2. In conclusion, these studies of the signal transduction activity of SAVICs in response to 5-HT have demonstrated that the 5-HT(2A)Rs are the most functionally active of the 5-HT(2)Rs in this cell type. Furthermore, 5-HT(2A)Rs are also involved in 5-HT up-regulation of active TGF-beta. 5-HT also mediated strong Erk 1/2 signaling via the MAP-kinase pathway, which was only in part because of 5-HT(2A)R activity. Thus, major 5-HT Erk 1/2 signaling beyond that controlled by 5-HT(2)Rs must involve other serotonin receptor types and/or secondary signaling events.
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PMID:Serotonin mechanisms in heart valve disease II: the 5-HT2 receptor and its signaling pathway in aortic valve interstitial cells. 1246 35

G-protein-coupled receptor 100 (GPR100) was discovered by searching the human genome database for novel G-protein-coupled peptide receptors. Full-length GPR100 was amplified from a cDNA library of the neuroendocrine cell line BON, which is derived from a human pancreas carcinoid. The open-reading frame, present on a single exon, coded for a protein of 374 amino acids with highest sequence identity (43%) to the human orphan somatostatin- and angiotensin-like peptide receptor. The analysis of chromosomal localisation mapped the GPR100 gene to chromosome 1q21.2-q21.3. The stable expression of GPR100 in Chinese hamster ovary cells together with aequorin as calcium sensor and the promiscuous G-protein subunit alpha16 as signal transducer revealed bradykinin and kallidin as effectors to elicit a calcium response. Dose-response curves yielded EC50 values for both ligands in the low nanomolar range, while the respective analogues without arginine at the carboxy-terminus were inactive. Calcium mobilisation was inhibited by the phospholipase C blocker U73122, but not by pertussis toxin, suggesting the involvement of the G-protein subunit alphaq and not alphai or alphao in signal transduction. In line with the main function of kinins as peripheral hormones, we found that GPR100 was expressed predominantly in tissues like pancreas, heart, skeletal muscle, salivary gland, bladder, kidney, liver, placenta, stomach, jejunum, thyroid gland, ovary, and bone marrow, but smaller amounts were also detected in the brain and in cell lines derived from tumours of various origins.
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PMID:Identification and characterisation of GPR100 as a novel human G-protein-coupled bradykinin receptor. 1453 Feb 18