scholarly journals Carbachol and histamine stimulation of guanine-nucleotide-dependent phosphoinositide hydrolysis in rat brain cortical membranes

1989 ◽  
Vol 261 (1) ◽  
pp. 29-35 ◽  
Author(s):  
E Claro ◽  
A Garcia ◽  
F Picatoste
Keyword(s):  
Rat Brain ◽  
Inositol Phosphates ◽  
Phosphoinositide Hydrolysis ◽  
Maximal Effect ◽  
Guanine Nucleotide ◽  
Effect Curve ◽  
Guanine Nucleotide Binding ◽  
Cortical Membranes ◽  
Nucleotide Binding Proteins ◽  
Stimulation Of

Guanine nucleotides have been shown to stimulate phosphoinositide breakdown in brain membranes, but no potentiation of such an effect by agonist was demonstrated. We have studied the effect of carbachol and histamine on guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulation of inositol phosphates formation in [3H]inositol-labelled rat brain cortical membranes. In this preparation, GTP[S] enhancement of phosphoinositide hydrolysis required the presence of MgATP and low Ca2+ concentration (100 nM). Carbachol potentiation of the GTP[S] effect was only observed when 1 mM-deoxycholate was also added. Under these conditions, stimulated production of [3H]inositol phosphates was linear for at least 15 min, and [3H]inositol bisphosphate [(3H]IP2) accounted for approx. 80%, whereas the amount of [3H]inositol trisphosphate [(3H]IP3) was very low. Stimulation by GTP[S] was concentration-dependent (half-maximal effect at 0.86 microM), and its maximal effect (815% over basal) was increased by 1 mM-carbachol (1.9-fold) and -histamine (1.7-fold). Both agonists decreased the slope index of the GTP[S] concentration/effect curve to values lower than unity, suggesting the appearance of some heterogeneity in the population of guanine-nucleotide-binding proteins (G-proteins) involved. The carbachol and histamine effects were also concentration-dependent, and were inhibited by atropine and mepyramine respectively. Fluoroaluminate stimulated phosphoinositide hydrolysis to a higher extent than GTP[S] plus carbachol, and these stimulations were not additive, indicating that the same polyphosphoinositide phospholipase C-coupled G-protein mediates both effects.

scholarly journals Guanine nucleotides stimulate production of inositol trisphosphate in rat cortical membranes

1985 ◽  
Vol 232 (3) ◽  
pp. 799-804 ◽  
Author(s):  
R A Gonzales ◽  
F T Crews
Keyword(s):  
Inositol Phosphates ◽  
Adenine Nucleotides ◽  
Inositol Trisphosphate ◽  
Guanine Nucleotides ◽  
Guanine Nucleotide ◽  
Inositol Phospholipids ◽  
Cortical Membranes ◽  
Gamma S ◽  
Hydrolysis Of ◽  
Stimulation Of

The guanine nucleotides guanosine 5′[beta, gamma-imido]triphosphate (Gpp[NH]p), guanosine 5′-[γ-thio]-triphosphate (GTP gamma S), GMP, GDP and GTP stimulated the hydrolysis of inositol phospholipids by a phosphodiesterase in rat cerebral cortical membranes. Addition of 100 microM-Gpp[NH]p to prelabelled membranes caused a rapid accumulation of [3H)inositol phosphates (less than 30 s) for up to 2 min. GTP gamma S and Gpp [NH]p caused a concentration-dependent stimulation of phosphoinositide phosphodiesterase with a maximal stimulation of 2.5-3-fold over control at concentrations of 100 microM. GMP was as effective as the nonhydrolysable analogues, but much less potent (EC50 380 microM). GTP and GDP caused a 50% stimulation of the phospholipase C at 100 microM and at higher concentrations were inhibitory. The adenine nucleotides App[NH]p and ATP also caused small stimulatory effects (64% and 29%). The guanine nucleotide stimulation of inositide hydrolysis in cortical membranes was selective for inositol phospholipids over choline-containing phospholipids. Gpp[NH]p stimulated the production of inositol trisphosphate and inositol bisphosphate as well as inositol monophosphate, indicating that phosphoinositides are substrates for the phosphodiesterase. EGTA (33 microM) did not prevent the guanine nucleotide stimulation of inositide hydrolysis. Calcium addition by itself caused inositide phosphodiesterase activation from 3 to 100 microM which was additive with the Gpp[NH]p stimulation. These data suggest that guanine nucleotides may play a regulatory role in the modulation of the activity of phosphoinositide phosphodiesterase in rat cortical membranes.

scholarly journals Effect of deoxycholate on guanine-nucleotide-dependent carbachol stimulation of phosphoinositidase C in mouse brain cortical membranes

1995 ◽  
Vol 312 (2) ◽  
pp. 445-449 ◽  
Author(s):  
N Bas ◽  
A Garcia
Keyword(s):  
G Protein ◽  
Mouse Brain ◽  
Bile Salts ◽  
Response Curve ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Guanine Nucleotide ◽  
Phosphoinositide Cycle ◽  
Cortical Membranes ◽  
Stimulation Of

Demonstration of guanine-nucleotide-dependent neurotransmitter stimulation of phosphoinositide breakdown in brain membranes has generally required the presence of the detergent, deoxycholate (DOC), in the assay medium. In the present study, by using mouse brain cortical membranes labelled with [3H]inositol in the presence of CMP through the reverse PtdIns synthase reaction, we have been able to show guanosine 5′-[gamma-thio]triphosphate (GTP[S])-dependent carbachol (CCh) stimulation of the formation of [3H]inositol phosphates in the absence of DOC and have studied how the detergent affects the response. The results of our study indicate that DOC affects the muscarinic receptor-G-protein-phosphoinositidase C (PIC) transduction system in several ways. First, it enhances agonist-induced PIC activity towards [3H]PtdInsP and [3H]PtdInsP2 and, secondly, it decreases the potency for GTP[S] stimulation of PIC, thus enhancing the agonist-induced leftward shift of the dose-response curve for GTP[S]. Additionally, DOC appears to increase the activity of the enzymes of the phosphoinositide cycle, PtdIns 4-kinase, Ins(1,4,5)P3 5-phosphatase and Ins(1,4)P2 1-phosphatase, thus altering the proportion of phosphoinositide substrates and inositol phosphate products. These observations advise caution in drawing conclusions about PIC substrate specificity and the potency of both guanine nucleotides and agonists from experiments performed in membranes in the presence of DOC or related bile salts.

UNCOUPLING OF RECEPTOR-MEDIATED CELLULAR RESPONSES BY IONIC LITHIUM

1989 ◽  
Vol 123 (2) ◽  
pp. R5-R7 ◽  
Author(s):  
M. Zaidi ◽  
A. Patchell ◽  
H.K. Datta ◽  
I. MacIntyre
Keyword(s):  
Signal Transduction ◽  
G Proteins ◽  
Cellular Responses ◽  
Receptor Interaction ◽  
Guanine Nucleotide ◽  
Protein Receptor ◽  
Guanine Nucleotide Binding ◽  
Cortical Membranes ◽  
Nucleotide Binding Proteins ◽  
Guanine Nucleotide Binding Proteins

ABSTRACT The propensity of ionic lithium to interfere with the coupling of receptors to guanine nucleotide binding proteins (G-proteins) has only recently been investigated using rat cortical membranes. In the present study we have used intact isolated osteoclasts to investigate lithium-induced uncoupling of the receptor-mediated actions of calcitonin. All actions of calcitonin on the osteoclast were abolished by ionic lithium. We believe that the cation prevents signal transduction by inhibiting G protein-receptor interaction, the first step in intracellular signalling.

scholarly journals A comparative study of endothelin- and platelet-activating-factor-mediated signal transduction and prostaglandin synthesis in rat Kupffer cells

1992 ◽  
Vol 281 (2) ◽  
pp. 485-492 ◽  
Author(s):  
C R Gandhi ◽  
K Stephenson ◽  
M S Olson
Keyword(s):  
Prostaglandin E2 ◽  
Phospholipase C ◽  
Kupffer Cells ◽  
Inositol Phosphates ◽  
Platelet Activating Factor ◽  
Phosphoinositide Metabolism ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Proteins ◽  
Hydrolysis Of ◽  
Stimulation Of

Endothelin-3 (ET-3) stimulated phosphoinositide metabolism and synthesis of prostaglandins in cultured rat Kupffer cells. ET-3-induced hydrolysis of phosphoinositides was characterized by the production of various inositol phosphates and of glycerophosphoinositol. The mechanism of ET-3-stimulated metabolism of phosphoinositides and synthesis of prostaglandins appeared to be distinct from the effect of platelet-activating factor (PAF) on these processes described previously [Gandhi, Hanahan & Olson (1990) J. Biol. Chem. 265, 18234-18241]. On a molar basis ET-3 was significantly more potent than PAF in stimulating phosphoinositide metabolism, e.g. ET-3-induced hydrolysis of phosphoinositides occurred at 1 pM, whereas PAF was ineffective at concentrations less than 1 nM. Upon challenging Kupffer cells with both ET-3 and PAF, an additive stimulation of phosphoinositide metabolism was observed, suggesting that the actions of these factors may be exerted on separate phosphoinositide pools. Treatment of Kupffer cells with pertussis toxin resulted in an inhibition of ET-3-induced phospholipase C activation; in contrast, cholera toxin treatment caused potentiation of ET-3-stimulated phospholipase C activity. Both toxins, however, inhibited PAF-stimulated phospholipase C activity. The present results suggest that the stimulatory effects of ET-3 and PAF on the phosphodiesteric metabolism of phosphoinositides in Kupffer cells require different guanine-nucleotide-binding proteins. Furthermore, the effects of bacterial toxins on ET-3- and PAF-induced phosphoinositide metabolism were not mediated by cyclic AMP. ET-3-induced metabolism of phosphoinositides was inhibited completely in Kupffer cells pretreated with ET-3, suggesting homologous ligand-induced desensitization of the ET-3 receptors. In contrast, similar experiments using PAF showed only a partial desensitization of subsequent PAF-induced phosphoinositide metabolism. In contrast to the increased production of prostaglandins E2 and D2 observed upon stimulation of Kupffer cells with PAF, ET-3 stimulated the biosynthesis of prostaglandin E2 only. Consistent with their additive effects on phosphoinositide metabolism, PAF and ET-3 exhibited an additive stimulation of the synthesis of prostaglandin E2.

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