scholarly journals Thrombin receptors modulate insulin-stimulated phosphatidylinositol 3,4,5-trisphosphate accumulation in 1321N1 astrocytoma cells

1996 ◽  
Vol 317 (2) ◽  
pp. 347-351 ◽  
Author(s):  
Ian H. BATTY ◽  
C. Peter DOWNES
Keyword(s):  
Insulin Receptors ◽  
Thrombin Receptor ◽  
Astrocytoma Cells ◽  
Thrombin Receptors ◽  
Transient Activation ◽  
Ligand Type ◽  
Insulin Receptor Signalling ◽  
Human Thrombin ◽  
Tethered Ligand ◽  
1321N1 Astrocytoma

Thrombin and insulin receptor signalling via phosphoinositide (PI)-specific phospholipase C (PLC) and PI 3-kinase was studied in [3H]inositol-labelled 1321N1 cells. Thrombin stimulated a dramatic, transient activation of PLC which is probably mediated via receptors of the ‘tethered-ligand’ type, since it was both reproduced by, and abolished following, pretreatment of cells with a synthetic peptide (SFLLRN) corresponding to the ligand domain of the human thrombin receptor. However, neither thrombin nor SFLLRN stimulated PI 3-kinase. By contrast, insulin did not influence [3H]InsP3 concentrations but stimulated accumulation of [3H]PtdIns(3,4,5)P3 and [3H]PtdIns(3,4)P2, the relative steady-state concentrations of which may indicate degradation of [3H]PtdIns(3,4,5)P3 by 5- and 3-phosphatases. The independent coupling of thrombin and insulin receptors to PLC and PI 3-kinase respectively in 1321N1 cells allowed interactions between these systems to be examined. Thus insulin-stimulated [3H]PtdIns(3,4,5)P3 accumulation was attenuated on co-stimulation of the thrombin receptor, whereas concentrations of [3H]PtdIns(3,4)P2 were transiently enhanced but then reduced. These results indicate that thrombin receptors in 1321N1 cells do not activate PI 3-kinase, but can modulate signalling by this enzyme.

scholarly journals Functional expression of a human thrombin receptor in Sf9 insect cells: evidence for an active tethered ligand

1996 ◽  
Vol 314 (2) ◽  
pp. 603-611 ◽  
Author(s):  
Xilin CHEN ◽  
Karen EARLEY ◽  
Weiping LUO ◽  
Sue-Hwa LIN ◽  
William P. SCHILLING
Keyword(s):  
Insect Cells ◽  
Recombinant Baculovirus ◽  
Sustained Response ◽  
Thrombin Receptor ◽  
Sf9 Cells ◽  
Thrombin Receptors ◽  
Sf9 Insect Cells ◽  
Human Thrombin ◽  
Hel Cells ◽  
Tethered Ligand

Desensitization of recombinant human thrombin receptors expressed in Sf9 insect cells was compared with native thrombin receptors in megakaryoblast erythroleukaemia (HEL) cells. Addition of thrombin (2 units/ml) or agonist peptide SFLLRN (10 μM) to HEL cells, or to Sf9 cells infected with recombinant baculovirus containing the thrombin receptor cDNA, produced an increase in the free cytosolic Ca2+ concentration ([Ca2+]i) as measured by fura-2. The response in HEL cells was transient, reflecting a rapid homologous desensitization. In contrast, [Ca2+]i in Sf9 cells expressing the thrombin receptor increased rapidly to a peak value that slowly declined, but remained elevated for at least 12 min following stimulation by thrombin. The sustained [Ca2+]i response to thrombin was not reversed by washout of thrombin or by subsequent addition of hirudin. Pretreatment of Sf9 cells with either thrombin (2 units/ml) or SFLLRN (10 or 50 μM) for 5 min produced a shift in the ED50 for SFLLRN (added 10 min after washout) from 0.4 μM to 20 and 7 μM, respectively. Thus, desensitization of thrombin receptors expressed in Sf9 cells occurs slowly and reflects a decrease in receptor affinity. The sustained [Ca2+]i response in Sf9 cells stimulated by thrombin may reflect continuous activation by the tethered ligand. To test this hypothesis, the effect of protease treatment during the sustained phase of the response was examined. Addition of either aminopeptidase M or thermolysin reversed the sustained response to SFLLRN, but only thermolysin reversed the sustained response to thrombin. Thermolysin had no effect on the change in [Ca2+]i observed following carbachol stimulation of Sf9 cells expressing the M5 muscarinic receptor. Furthermore, following thermolysin treatment, the cells remained responsive to a subsequent application of SFLLRN. These results demonstrate that the tethered ligand remains active for extended periods of time after thrombin stimulation and suggests that further hydrolysis by extracellular proteases may represent an important mechanism of rapid receptor deactivation.

scholarly journals Coupling of the thrombin receptor to G12 may account for selective effects of thrombin on gene expression and DNA synthesis in 1321N1 astrocytoma cells.

1996 ◽  
Vol 7 (11) ◽  
pp. 1679-1690 ◽  
Author(s):  
G R Post ◽  
L R Collins ◽  
E D Kennedy ◽  
S A Moskowitz ◽  
A M Aragay ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Pertussis Toxin ◽  
Mitogen Activated Protein Kinase ◽  
Thrombin Receptor ◽  
Protein Kinase Activity ◽  
Astrocytoma Cells ◽  
Mitogen Activated Protein ◽  
1321N1 Astrocytoma

In 1321N1 astrocytoma cells, thrombin, but not carbachol, induces AP-1-mediated gene expression and DNA synthesis. To understand the divergent effects of these G protein-coupled receptor agonists on cellular responses, we examined Gq-dependent signaling events induced by thrombin receptor and muscarinic acetylcholine receptor stimulation. Thrombin and carbachol induce comparable changes in phosphoinositide and phosphatidylcholine hydrolysis, mobilization of intracellular Ca2+, diglyceride generation, and redistribution of protein kinase C; thus, activation of these Gq-signaling pathways appears to be insufficient for gene expression and mitogenesis. Thrombin increases Ras and mitogen-activated protein kinase activation to a greater extent than carbachol in 1321N1 cells. The effects of thrombin are not mediated through Gi, since ribosylation of Gi/Go proteins by pertussis toxin does not prevent thrombin-induced gene expression or thrombin-stimulated DNA synthesis. We recently reported that the pertussis toxin-insensitive G12 protein is required for thrombin-induced DNA synthesis. We demonstrate here, using transfection of receptors and G proteins in COS-7 cells, that G alpha 12 selectively couples the thrombin receptor to AP-1-mediated gene expression. This does not appear to result from increased mitogen-activated protein kinase activity but may reflect activation of a tyrosine kinase pathway. We suggest that preferential coupling of the thrombin receptor to G12 accounts for the selective ability of thrombin to stimulate Ras, mitogen-activated protein kinase, gene expression, and mitogenesis in 1321N1 cells.

scholarly journals Changes in the structure and function of the human thrombin receptor during receptor activation, internalization, and recycling.

1994 ◽  
Vol 269 (4) ◽  
pp. 2943-2952
Author(s):  
L.F. Brass ◽  
S. Pizarro ◽  
M. Ahuja ◽  
E. Belmonte ◽  
N. Blanchard ◽  
...  
Keyword(s):  
Receptor Activation ◽  
Structure And Function ◽  
Thrombin Receptor ◽  
Human Thrombin ◽  
And Function

scholarly journals Caveolin-1 Regulates P2Y2 Receptor Signaling during Mechanical Injury in Human 1321N1 Astrocytoma

Biomolecules ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 622
Author(s):  
Magdiel Martínez ◽  
Namyr A. Martínez ◽  
Jorge D. Miranda ◽  
Héctor M. Maldonado ◽  
Walter I. Silva Ortiz
Keyword(s):  
Cell Viability ◽  
Mechanical Injury ◽  
P2y2 Receptor ◽  
Caspase 9 ◽  
Post Injury ◽  
Caveolin 1 ◽  
Receptor Coupling ◽  
Downstream Signaling ◽  
Astrocytoma Cells ◽  
1321N1 Astrocytoma

Caveolae-associated protein caveolin-1 (Cav-1) plays key roles in cellular processes such as mechanosensing, receptor coupling to signaling pathways, cell growth, apoptosis, and cancer. In 1321N1 astrocytoma cells Cav-1 interacts with the P2Y2 receptor (P2Y2R) to modulate its downstream signaling. P2Y2R and its signaling machinery also mediate pro-survival actions after mechanical injury. This study determines if Cav-1 knockdown (KD) affects P2Y2R signaling and its pro-survival actions in the 1321N1 astrocytoma cells mechanical injury model system. KD of Cav-1 decreased its expression in 1321N1 cells devoid of or expressing hHAP2Y2R by ~88% and ~85%, respectively. Cav-1 KD had no significant impact on P2Y2R expression. Post-injury densitometric analysis of pERK1/2 and Akt activities in Cav-1-positive 1321N1 cells (devoid of or expressing a hHAP2Y2R) revealed a P2Y2R-dependent temporal increase in both kinases. These temporal increases in pERK1/2 and pAkt were significantly decreased in Cav-1 KD 1321N1 (devoid of or expressing a hHAP2Y2R). Cav-1 KD led to an ~2.0-fold and ~2.4-fold decrease in the magnitude of the hHAP2Y2R-mediated pERK1/2 and pAkt kinases’ activity, respectively. These early-onset hHAP2Y2R-mediated signaling responses in Cav-1-expressing and Cav-1 KD 1321N1 correlated with changes in cell viability (via a resazurin-based method) and apoptosis (via caspase-9 expression). In Cav-1-positive 1321N1 cells, expression of hHAP2Y2R led to a significant increase in cell viability and decreased apoptotic (caspase-9) activity after mechanical injury. In contrast, hHAP2Y2R-elicited changes in viability and apoptotic (caspase-9) activity were decreased after mechanical injury in Cav-1 KD 1321N1 cells expressing hHAP2Y2R. These findings support the importance of Cav-1 in modulating P2Y2R signaling during mechanical injury and its protective actions in a human astrocytoma cell line, whilst shedding light on potential new venues for brain injury or trauma interventions.

scholarly journals An autoantibody directed against human thrombin anion-binding exosite in a patient with arterial thrombosis: effects on platelets, endothelial cells, and protein C activation

Blood ◽  
1994 ◽  
Vol 84 (6) ◽  
pp. 1843-1850 ◽  
Author(s):  
E Arnaud ◽  
M Lafay ◽  
P Gaussem ◽  
V Picard ◽  
M Jandrot-Perrus ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Arterial Thrombosis ◽  
Protein C ◽  
Receptor Activation ◽  
Anion Binding ◽  
Thrombin Receptor ◽  
Cell Functions ◽  
Human Thrombin

Abstract An autoantibody, developed by a patient with severe and recurrent arterial thrombosis, was characterized to be directed against the anion- binding exosite of thrombin, and inhibited all thrombin interactions requiring this secondary binding site without interfering with the catalytic site. The effect of the antibody was studied on thrombin interactions with platelets and endothelial cells from human umbilical veins (HUVEC). The autoantibody specifically and concentration- dependently inhibited alpha-thrombin-induced platelet activation and prostacyclin (PGI2) synthesis from HUVEC. It had no effect when gamma- thrombin or the thrombin receptor activation peptide SFLLR were the inducers. The effect of the antibody on protein C activation has been studied. The antibody blocked the thrombin-thrombomodulin activation of protein C. The inhibition of the activation was maximal with a low concentration of thrombomodulin. The fact that the autoantibody inhibited concentration-dependent alpha-thrombin-induced platelet and endothelial cell functions emphasizes the crucial role of the anion- binding exosite of thrombin to activate its receptor. In regard to the pathology, the antibody inhibited two vascular processes implicated in thrombin-antithrombotic functions, PGI2 secretion, and protein C activation, which could be implicated in this arterial thrombotic disease.

The functional thrombin receptor is associated with the plasmalemma and a large endosomal network in cultured human umbilical vein endothelial cells

1995 ◽  
Vol 108 (3) ◽  
pp. 1155-1164 ◽  
Author(s):  
R. Horvat ◽  
G.E. Palade
Keyword(s):  
Endothelial Cells ◽  
Umbilical Vein ◽  
Morphological Evidence ◽  
Thrombin Receptor ◽  
Human Umbilical Vein ◽  
Cultured Endothelial Cells ◽  
Human Thrombin ◽  
Membrane Spanning ◽  
Umbilical Vein Endothelial Cells ◽  
G Protein Coupled

The functional thrombin receptor, normally expressed by endothelial cells and platelets, is a member of the G protein-coupled, seven membrane-spanning-domain receptor family and is thought to be responsible for most, if not all, the cell stimulatory effects of thrombin. Upon binding, thrombin cleaves the receptor's N-terminal ectodomain, unmasking a new N terminus, which by itself activates the receptor. Using antibodies to different domains of the human thrombin receptor, we have localized the receptor in cultured human umbilical vein endothelial cells by indirect immunofluorescence and immunoelectron microscopy. We found the receptor expressed on the plasmalemma of cultured endothelial cells in individual units rather than in clusters, at lower concentration than, and at different sites from, thrombomodulin. We also found the receptor associated with a distinct, intracellular, transferrin receptor-containing, tubulovesicular network. The thrombin receptor-positive structure spread from the perinuclear region to the periphery of the cells, exhibiting a number of varicosities interconnected by branching tubular elements, strikingly similar to an image recently described for a continuous endosomal reticulum. Our results provide morphological evidence for the presence of the functional thrombin receptor at relative low density on the surface of cultured endothelial cells (compared to thrombomodulin) and in relatively large quantities inside the cells, associated with an endosomal compartment.

Intramolecular Diels-Alder Cycloaddition: 7-Isocyanoamphilecta- 11(20),15-diene (Miyaoka), (–)-Scabronine G (Kanoh), Basiliolide B (Stoltz), Hirsutellone B (Uchiro), Echinopine A (Chen)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Neurotrophic Factors ◽  
Claisen Rearrangement ◽  
Diels Alder ◽  
Relative Configuration ◽  
Intramolecular Cycloaddition ◽  
Quaternary Centers ◽  
Astrocytoma Cells ◽  
National University ◽  
Seoul National University ◽  
1321N1 Astrocytoma

The amphilectane diterpenes, exemplified by 7-isocyanoamphilecta-11(20),15-diene 3, have been little investigated. In the course of a synthesis of 3, Hiroaki Miyaoka of the Tokyo University of Pharmacy and Life Sciences took advantage (Synlett 2011, 547) of the kinetic enolization and silylation of 1 to convert it into a trienone that spontaneously cyclized to 2. Scabronine G 6, isolated from the mushroom Sarcodon scabrosus, was found to enhance the secretion of neurotrophic factors from 1321N1 astrocytoma cells. To set the absolute configuration of the two quaternary centers that are 1, 4 on the cyclohexane ring of 6, Naoki Kanoh and Yoshiharu Iwabuchi of Tohoku University cyclized (Org. Lett. 2011, 13, 2864) 4 to 5. Although described by the authors as a double Michael addition, this transformation has the same connectivity as an intramolecular Diels-Alder cycloaddition. The diterpenes isolated from the genus Thapsia, represented by basiliolide B 9, induce rapid mobilization of intracellular Ca2+ stores. Brian M. Stoltz of Caltech effected (Angew. Chem. Int. Ed. 2011, 50, 3688) Claisen rearrangement of 7 to give an intermediate that cyclized to 8 as a mixture of diastereomers. A significant challenge in the synthesis was the assembly of the delicate enol ether/lactone of 9. Hirsutellone B 12, isolated from Hirsutella nivea, shows significant antituberculosis activity. Hiromi Uchiro of the Tokyo University of Science found it useful (Org. Lett. 2011, 13, 6268) to protect the intermediate unsaturated keto ester by intermolecular cycloaddition with pentamethylcyclopentadiene before constructing the triene of 10. Simple thermolysis reversed the intermolecular addition, opening the way to intramolecular cycloaddition to give 11. The tetracyclic ring system of the diterpene echinopine A 15 represents a substantial synthetic challenge. David Y.-K. Chen of Seoul National University approached this problem (Org. Lett. 2011, 13, 5724) by Pd-mediated cyclization of 13 to the diene, which then underwent intramolecular Diels-Alder cycloaddition to give 14, with control of the relative configuration of two of the three ternary centers of 15. Double bond migration followed by oxidative cleavage of the resulting cyclohexenone then set the stage for the intramolecular cyclopropanation that completed the synthesis of 15.

Thrombin receptor-activating peptide sensitizes the human endothelial thrombin receptor

1995 ◽  
Vol 268 (1) ◽  
pp. C36-C44 ◽  
Author(s):  
H. J. Kruse ◽  
C. Mayerhofer ◽  
W. Siess ◽  
P. C. Weber
Keyword(s):  
Endothelial Cells ◽  
Ligand Binding ◽  
Umbilical Vein ◽  
Thrombin Receptor ◽  
Receptor Desensitization ◽  
Short Term ◽  
Tethered Ligand ◽  
Continuous Presence ◽  
Sensitizing Effect ◽  
Umbilical Vein Endothelial Cells

Receptor-operated effects of alpha-thrombin and of the thrombin receptor-activating peptide TRAP14 on cytoplasmic Ca2+ concentration ([Ca2+]i) were examined in fura 2-loaded endothelial cells. Experiments with hirudin showed that alpha-thrombin-induced Ca2+ influx requires the continuous presence of active alpha-thrombin. YFLLRNP, known to antagonize alpha-thrombin- and TRAP7-induced [Ca2+]i transients in platelets, did not antagonize [Ca2+]i transients in response to alpha-thrombin and TRAP14 in human umbilical vein endothelial cells (HUVEC). Repetitive short-term stimulations with alpha-thrombin desensitized [Ca2+]i transients to subsequent stimulations with either alpha-thrombin or TRAP14. In contrast, repeated short-term stimulations with TRAP14 sensitized [Ca2+]i transients to subsequent stimulations with either agonist. Blockade of Ca2+ influx by SKF-96365 abolished the sensitizing effect of TRAP14. The results indicate distinct characteristics of platelet and endothelial thrombin receptors and suggest that alpha-thrombin and TRAP14 activate the receptor differently. It appears that receptor desensitization occurs independently of TRAP14 binding and, hence, tethered ligand binding to and activation of the receptor. Persistent receptor desensitization after alpha-thrombin seems to depend on both alpha-thrombin binding to the hirudin-like receptor domain and the irreversible proteolytic cleavage of the receptor. It does not involve the TRAP14/tethered ligand binding site of the receptor. TRAP14 primes the receptor by a mechanism mediated by Ca2+ influx.

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