Carbachol-induced desensitization of PLC-β pathway in rat myometrium: downregulation of Gqα/G11α

1998 ◽  
Vol 275 (3) ◽  
pp. C636-C645 ◽  
Author(s):  
Sandrine Lajat ◽  
Simone Harbon ◽  
Zahra Tanfin
Keyword(s):  
Binding Sites ◽  
Prolonged Exposure ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Initial Period ◽  
Kinase C ◽  
Inositol Phosphate Production ◽  
Muscarinic Binding Sites ◽  
Heterologous Desensitization ◽  
Delayed Phase

In the estrogen-treated rat myometrium, carbachol increased the generation of inositol phosphates by stimulating the muscarinic receptor-Gq/G11-phospholipase C-β3 (PLC-β3) cascade. Exposure to carbachol resulted in a rapid and specific (homologous) attenuation of the subsequent muscarinic responses in terms of inositol phosphate production, PLC-β3 translocation to membrane, and contraction. Refractoriness was accompanied by a reduction of membrane muscarinic binding sites and an uncoupled state of residual receptors. Protein kinase C (PKC) altered the functionality of muscarinic receptors and contributed to the initial period of desensitization. A delayed phase of the muscarinic refractoriness was PKC independent and was associated with a downregulation of Gqα/G11α. Atropine failed to induce desensitization as well as Gqα/G11α downregulation, indicating that both events involve active occupancy of the receptor. Prolonged exposure to A[Formula: see text] reduced subsequent A[Formula: see text] as well as carbachol-mediated inositol phosphate responses and similarly induced downregulation of Gqα/G11α. Data suggest that a decrease in the level of Gqα/G11α is subsequent to its activation and may account for heterologous desensitization.

scholarly journals Scrape-loaded p21ras down-regulates agonist-stimulated inositol phosphate production by a mechanism involving protein kinase C

1989 ◽  
Vol 260 (1) ◽  
pp. 157-161 ◽  
Author(s):  
B D Price ◽  
J D H Morris ◽  
C J Marshall ◽  
A Hall
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Inositol Phosphate ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Ras Protein ◽  
Kinase C ◽  
Inositol Phosphate Production ◽  
Ligand Stimulation ◽  
Scrape Loading

The effect of scrape-loaded [Val-12]p21ras on agonist-stimulated phosphatidylinositol 4,5-bisphosphate (PIP2) turnover in Swiss-3T3 cells was studied. Previously [Morris, Price, Lloyd, Marshall & Hall (1989) Oncogene 4, 27-31] we demonstrated that [Val-12]p21ras activates protein kinase C within 10 min of scrape loading. Here, we show that [Val-12]p21ras inhibits bombesin and platelet-derived growth factor-stimulated PIP2 breakdown 1.5-4 h after scrape loading. This effect persisted for at least 18 h and could be mimicked in control cells by activation of protein kinase C with 12-O-tetradecanoyl 13-acetate (TPA) 15 min prior to ligand stimulation. When protein kinase C was down-regulated by chronic TPA treatment, [Val-12]p21ras was no longer able to inhibit agonist-stimulated inositol phosphate production. These results indicate that changes in inositol phosphate levels caused by ras protein are probably due to activation of protein kinase C and not to an interaction of ras with phospholipase C.

Frog glomerular vasotocin receptors resemble mammalian V1b receptors

1994 ◽  
Vol 267 (5) ◽  
pp. R1198-R1208 ◽  
Author(s):  
A. Ammar ◽  
R. M. Rajerison ◽  
S. Roseau ◽  
M. Bloch-Faure ◽  
D. Butlen
Keyword(s):  
Binding Sites ◽  
Inositol Phosphate ◽  
Rank Order ◽  
Enzyme Activation ◽  
Arginine Vasotocin ◽  
Pharmacological Properties ◽  
Nephron Segments ◽  
Inositol Phosphate Production ◽  
Vasopressin Receptors ◽  
Stimulation Of

Vasotocin receptors were investigated in glomeruli and nephron segments microdissected from collagenase-treated kidneys of Rana ridibunda, using [d(CH2)5Tyr(Me)2,Thr4,Orn8,125I-Tyr-NH2(9)]vasotocin (125I-OVTA) as a radioligand. Specific 125I-OVTA binding sites were found only in glomeruli and not in all tubule segments tested. Glomerular receptors exhibited the following stereospecificity for recognition of vasotocin analogues: Tyr-NH2(9)-LA-V1a > 125I-OVTA > arginine vasotocin (AVT) > or = [d(CH2)5Tyr-(Me)2]AVP > OVTA > or = [Phe2,Orn8]VT > oxytocin (OT) > or = [d(CH2)5-Sar7]AVP > desGly9[d(CH2)5Tyr(Et)2]VAVP > or = [d(CH2)5Tyr(Et)2]VAVP > AVP > [1-desamino-8-D-arginine]vasopressin (DDAVP) > [Thr4,Gly7]OT. In addition, vasotocin enhanced [3H]inositol phosphate production in sieved glomeruli labeled with myo-[3H]inositol; the rank order of structural vasotocin analogues for stimulation of phosphoinositidase C was [Phe2,Orn8]VT > AVT > OT > AVP > DDAVP, whereas [Thr4,Gly7]OT was almost inactive, and the rank order of antagonists for inhibition of hormone-induced enzyme activation was Tyr-NH2(9)-LA-V1a > [d(CH2)5Tyr(Me)2]AVP = OVTA > [d(CH2)5Sar7]AVP > [d(CH2)5Tyr(Et)2]VAVP > or = desGly9[d(CH2)5Tyr(Et)2]VAVP. Results indicate that the 125I-OVTA-labeled binding sites detected in frog glomeruli reveal the pharmacological properties of mammalian V1b-pituitary vasopressin receptors and might be physiological vasotocin receptors involved in phosphoinositidase C stimulation.

Oxytocin and vasopressin stimulate inositol phosphate production in human gestational myometrium and decidua cells

1986 ◽  
Vol 6 (7) ◽  
pp. 613-619 ◽  
Author(s):  
Michael P. Schrey ◽  
Alison M. Read ◽  
Philip J. Steer
Keyword(s):  
Arachidonic Acid ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Diacylglycerol Lipase ◽  
Inositol 1 ◽  
Inositol Phosphate Production ◽  
Acid Accumulation ◽  
Free Arachidonic Acid ◽  
Hydrolysis Of ◽  
Related Increase

The involvement of phosphoinositide hydrolysis in the action of oxytocin and vasopressin on the uterus was investigated in gestational myometrium and decidua cells by measuring the production of inositol phosphates. Both peptides stimulated a dose related increase in all three inositol phosphates in myometrium. This may be related to the control of sarcoplasmic Ca++ levels in the myometrium. Oxytocin and vasopressin also stimulated inositol 1-phosphate (IP) production in decidua cells. The hydrolysis of phosphatidylinositol by decidua homogenates exhibited a precursor-product relationship for diacylglycerol and arachidonic acid accumulation. Hence both peptides may mobilise free arachidonic acid, for prostaglandin biosynthesis, from decidua cell phosphoinositides by the sequential action of phospholipase C and diacylglycerol lipase.

scholarly journals G-proteins are not directly involved in the CD3-antigen-mediated production of inositol phosphates in HPB-ALL T-leukaemia cells expressing phospholipase C isoforms γ1 and β3

1993 ◽  
Vol 289 (2) ◽  
pp. 387-394 ◽  
Author(s):  
M Biffen ◽  
M Shiroo ◽  
D R Alexander
Keyword(s):  
Phospholipase C ◽  
Tyrosine Phosphorylation ◽  
G Protein ◽  
G Proteins ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Cross Linking ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine ◽  
Inositol Phosphate Production

The possible involvement of G-proteins in T cell antigen-receptor complex (TCR)-mediated inositol phosphate production was investigated in HPB-ALL T-cells, which were found to express the phospholipase C gamma 1 and beta 3 isoforms. Cross-linking the CD3 antigen on streptolysin-O-permeabilized cells stimulated a dose-dependent increase in inositol phosphate production, as did addition of guanosine 5′-[gamma-thio]triphosphate (GTP[S]) or vanadate, a phosphotyrosine phosphatase inhibitor. It was possible, therefore, that the CD3-antigen-mediated production of inositol phosphates was either via a G-protein-dependent mechanism or by stimulation of protein tyrosine phosphorylation. The CD3-induced inositol phosphate production was potentiated by addition of vanadate, but not by addition of GTP[S]. Guanosine 5′-[beta-thio]diphosphate (GDP[S]) inhibited the rise in inositol phosphates induced by GTP[S], vanadate or cross-linking the CD3 antigen. The increase in protein tyrosine phosphorylation stimulated by vanadate or the OKT3 monoclonal antibody was not observed in the presence of GDP[S], showing that in permeabilized HPB-ALL cells, GDP[S] inhibits the actions of tyrosine kinases as well as G-protein function. Addition of either ADP[S] or phenylarsine oxide inhibited CD3- and vanadate-mediated increases in both tyrosine phosphorylation and inositol phosphate production, but did not inhibit GTP[S]-stimulated inositol phosphate production. On the other hand, pretreatment of cells with phorbol 12,13-dibutyrate inhibited subsequent GTP[S]-stimulated inositol phosphate production but did not inhibit significantly inositol phosphate production stimulated by either OKT3 F(ab')2 fragments or vanadate. Our results are consistent with the CD3 antigen stimulating inositol phosphate production by increasing the level of protein tyrosine phosphorylation, but not by activating a G-protein.

Dopamine does not attenuate phosphoinositide hydrolysis in rat anterior pituitary cells

1986 ◽  
Vol 110 (3) ◽  
pp. 389-393 ◽  
Author(s):  
P. L. Canonico ◽  
W. D. Jarvis ◽  
A. M. Judd ◽  
R. M. MacLeod
Keyword(s):  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
Marked Diminution ◽  
Inositol Phosphate Production ◽  
Concomitant Reduction ◽  
Potent Agonist ◽  
Hydrolysis Of

ABSTRACT The hydrolysis of membrane phosphatidylinositol to yield [3H]labelled inositol phosphates by anterior pituitary cells was stimulated significantly by angiotensin II, TRH and neurotensin over a broad range of concentrations. These secretagogues also stimulated release of prolactin. Although the coincident incubation of dopamine with these agents resulted in a marked diminution of prolactin release, no concomitant reduction in inositol phosphate production was observed. In addition, bromocriptine, a potent agonist of dopamine, also proved ineffective in blunting stimulated phosphatidylinositol catabolism. Although it slightly inhibited basal rates of inositol tris-, bis- and monophosphate production, these results show that the secretagogue-mediated enhancement of phosphatidylinositol catabolism may be correlated with an increased release of prolactin and that the inhibition of hormone release produced by dopamine is not achieved by reducing basal or secretagogue-mediated inositol phosphate production. J. Endocr. (1986) 110, 389–393

scholarly journals Changes in free cytosolic calcium and accumulation of inositol phosphates in isolated hepatocytes by [Leu]enkephalin

1986 ◽  
Vol 238 (2) ◽  
pp. 537-542 ◽  
Author(s):  
R P Leach ◽  
S B Shears ◽  
C J Kirk ◽  
M A Titheradge
Keyword(s):  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Cytosolic Calcium ◽  
Isolated Hepatocytes ◽  
Opioid Peptide ◽  
Alpha Activity ◽  
Dose Dependency ◽  
Significant Stimulation ◽  
Inositol Phosphate Production ◽  
Stimulation Of

Isolated hepatocytes from fed rats were used to study the effects of the opioid peptide [Leu]enkephalin on intracellular free cytosolic Ca2+ ([Ca2+]i) and inositol phosphate production. By measuring the fluorescence of the intracellular Ca2+-selective indicator quin-2, [Leu]enkephalin was found to increase [Ca2+]i rapidly from a resting value of 0.219 microM to 0.55 microM. The magnitude of this response was comparable with that produced by maximally stimulating concentrations of either vasopressin (100 nM) or phenylephrine (10 microM). The opioid-peptide-mediated increase in [Ca2+]i showed a dose-dependency comparable with the activation of phosphorylase, but it preceded the increase in phosphorylase alpha activity. Addition of [Leu]enkephalin to hepatocytes prelabelled with myo-[2-3H(n)]inositol resulted in a significant stimulation of inositol phosphate production. At 10 min after hormone addition, there were increases in the concentrations of inositol mono-, bis- and tris-phosphate fractions of 12-, 9- and 14-fold respectively. No effect was apparent on the glycerophosphoinositol fraction. The effect of 10 microM-[Leu]enkephalin on inositol phosphate production was significantly greater than that obtained with 10 microM-phenylephrine, but marginally smaller than that induced by 100 nM-vasopressin. However, at these concentrations all three agonists gave a comparable increase in [Ca2+]i and activation of phosphorylase a. These data provide evidence for [Leu]enkephalin acting via a mechanism involving a mobilization of Ca2+ as a result of increased phosphatidylinositol turnover.

scholarly journals Differences in the regulation of endothelin-1- and lysophosphatidic-acid-stimulated Ins(1,4,5)P3 formation in rat-1 fibroblasts

1991 ◽  
Vol 280 (3) ◽  
pp. 609-615 ◽  
Author(s):  
R Plevin ◽  
E E MacNulty ◽  
S Palmer ◽  
M J O Wakelam
Keyword(s):  
Phospholipase C ◽  
Lysophosphatidic Acid ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Regulatory Protein ◽  
Permeabilized Cells ◽  
Endothelin 1 ◽  
Kinase C ◽  
Guanine Nucleotide Binding ◽  
Dose Dependent

Endothelin-1 (ET-1)- and lysophosphatidic acid (LPA)-stimulated PtdIns(4,5)P2 hydrolysis has been studied in Rat-1 fibroblasts. Although both agonists caused the dose-dependent accumulation of inositol phosphates, a number of differences were observed. LPA induced a transient increase in Ins(1,4,5)P3 mass which returned to basal levels within 90 s, whereas the response to ET-1 did not desensitize, with levels remaining at 3-4 times basal values for up to 15 min. Stimulated decreases in mass levels of PtdIns(4,5)P2 mirrored Ins(1,4,5)P3 formation for both agonists. Experiments with electropermeabilized cells demonstrated that the effects of both agonists are stimulated by a phospholipase C controlled by a guanine-nucleotide-binding regulatory protein; however, there are differences in the nature of these interactions. The inositol phosphate response to ET-1 is poorly potentiated by guanosine 5′-[gamma-thio]triphosphate (GTP[S]) and markedly inhibited by guanosine 5′-[beta-thio]diphosphate (GDP[S]), whereas that to LPA is potentiated by GTP[S] but is relatively insensitive to GDP[S]. In addition, LPA decreased the lag time for the onset of GTP[S]-stimulated [3H]InsP3 accumulation, whereas ET-1 was without effect. Phorbol 12-myristate 13-acetate treatment of the cells inhibited LPA-stimulated, but not ET-1-stimulated, inositol phosphate formation in both intact and permeabilized cells, suggesting that the site of protein kinase C-mediated phosphorylation may be blocked in ET-1-stimulated Rat-1 cells. The results indicate that the receptor-G-protein-phospholipase C interaction for the two agonists may not conform to the same model.

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