Phospholipase C-dependent phosphoinositide breakdown induced by ELF-EMF in Peganum harmala calli

Biochimie ◽  
2004 ◽  
Vol 86 (4-5) ◽  
pp. 343-349 ◽  
Author(s):  
Maria Piera Piacentini ◽  
Elena Piatti ◽  
Daniele Fraternale ◽  
Donata Ricci ◽  
Maria Cristina Albertini ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Peganum Harmala ◽  
Phosphoinositide Breakdown

Phosphoinositide breakdown in blowfly salivary glands

1984 ◽  
Vol 246 (1) ◽  
pp. C141-C147 ◽  
Author(s):  
I. Litosch ◽  
H. S. Lee ◽  
J. N. Fain
Keyword(s):  
Salivary Glands ◽  
Phospholipase C ◽  
Inositol Phosphates ◽  
Ionophore A23187 ◽  
Phosphoinositide Breakdown ◽  
Transient Loss ◽  
Phosphatidylinositol 4

In blowfly salivary glands, 5-hydroxytryptamine stimulated a rapid and sustained loss of [3H]inositol, [32P]phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate. There was a corresponding increase in labeled inositol phosphates. In the absence of Ca2+, 5-hydroxytryptamine stimulated a rapid but transient loss of labeled phosphatidylinositol 4,5-bisphosphate. By 5 min, the amount of labeled phosphatidylinositol 4,5-bisphosphate recovered to control values. The divalent ionophore A23187 stimulated loss of labeled phosphatidylinositol 4,5-bisphosphate and increased the amount of labeled phosphatidylinositol. In homogenates, Ca2+ stimulated phosphatidylinositol 4,5-bisphosphate breakdown but not phosphatidylinositol breakdown. These results suggest that hormone-stimulated breakdown of labeled phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate occurs through a phospholipase C and is relatively independent of extracellular Ca2+. There is also a Ca2+-activated conversion of phosphatidylinositol 4,5-bisphosphate to phosphatidylinositol.

Vasopressin receptors and inositol trisphosphate production in blood vessels of spontaneously hypertensive rats

1989 ◽  
Vol 67 (3) ◽  
pp. 232-239 ◽  
Author(s):  
Richard Larivière ◽  
Johanne Baribeau ◽  
Jean St-Louis ◽  
Ernesto L. Schiffrin
Keyword(s):  
Blood Pressure ◽  
Phospholipase C ◽  
Binding Sites ◽  
Spontaneously Hypertensive Rats ◽  
Pressor Response ◽  
Inositol Trisphosphate ◽  
Normal Density ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Phosphoinositide Breakdown

To understand the regulation of vasopressin (AVP) receptors in spontaneous hypertension, we investigated the pressor response of AVP in the perfused mesenteric vasculature, AVP binding sites in the membrane preparation of the same vascular bed, and the production of inositol trisphosphate (InsP3) stimulated by AVP in the aorta of spontaneously hypertensive rats (SHR), Wistar–Kyoto rats (WKY), and Wistar rats (WR) at different ages (4–16 weeks). Plasma AVP concentrations were similar in SHR, WKY, and WR at all ages. The density of AVP vascular binding sites was significantly higher in WKY than in SHR and WR at 12 weeks. Receptor affinity was similar in all strains. The pressor response of the mesenteric vasculature to AVP was similar in the three strains of rats at 4 weeks (prehypertensive stage) and increased progressively in SHR compared with WKY and WR at 8 and 12 weeks of age by 43 and 35%, respectively, and by more than 80% at 16 weeks of age (established hypertensive stage). There was no difference in vascular sensitivity to AVP. A significantly increased pressor response to a supramaximal dose of norepinephrine was also found at 16 weeks in SHR, but not in younger rats. InsP3 production in the aorta in response to AVP was increased in SHR at 8, 12, and 16 weeks, compared with WKY and WR. These results suggest that the vascular response to AVP is increased in SHR, in spite of decreased or normal density of binding sites compared with WKY or WR. The increased responsiveness to AVP in SHR may be mediated in part by the enhanced activity of AVP receptor-coupled phospholipase C, resulting in increased membrane phosphoinositide breakdown and inositol trisphosphate production, which may play a role in the elevation of blood pressure in SHR.Key words: vascular reactivity, vasopressin binding sites, phosphoinositide breakdown, phospholipase C, high blood pressure.

scholarly journals Reconstitution of thromboxane A2 receptor-stimulated phosphoinositide hydrolysis in isolated platelet membranes: involvement of phosphoinositide-specific phospholipase C-β and GTP-binding protein Gq

1993 ◽  
Vol 291 (1) ◽  
pp. 235-240 ◽  
Author(s):  
J J Baldassare ◽  
A P Tarver ◽  
P A Henderson ◽  
W M Mackin ◽  
B Sahagan ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Binding Proteins ◽  
Thromboxane A2 ◽  
Human Platelets ◽  
Phosphoinositide Hydrolysis ◽  
Arachidonic Acid Metabolite ◽  
Thromboxane A2 Receptor ◽  
Gtp Binding Proteins ◽  
Phosphoinositide Breakdown ◽  
Gtp Binding

Activation of human platelets by the arachidonic acid metabolite thromboxane A2 and the thromboxane A2 mimic U46619 is mediated through phosphoinositide-specific phospholipase C-catalysed hydrolysis of phosphoinositides. We have established conditions to reconstitute U46619-stimulated phosphoinositide breakdown by addition of guanine nucleotides and soluble platelet phospholipase C activities to isolated 32P-labelled membranes. Receptor-activated phosphoinositide hydrolysis was observed in the presence of guanosine 5′-[gamma-thio]triphosphate (GTP[S]) or GTP plus U46619. Phosphoinositide hydrolysis was dependent on both GTP and U46619, with half-maximal stimulation observed at 5 microM and 500 nM respectively. Phospholipase C isoenzymes beta, gamma 1, gamma 2 and delta were purified from platelet cytosol and their ability to reconstitute GTP[S]-dependent and GTP/U46619-dependent phosphoinositide hydrolysis determined. Phospholipase C-beta and -delta, but not phospholipase C-gamma 1 or -gamma 2, catalysed phosphoinositide breakdown in the presence of GTP[S]. In contrast, only phospholipase C-beta was able to reconstitute GTP-dependent U46619-induced hydrolysis. The participation of GTP-regulatory proteins in the reconstitution of GTP[S]- and GTP/U46619-induced phosphoinositide hydrolysis was examined using antibodies to the C-terminals of the alpha-subunits of three of the heterotrimeric GTP-binding proteins expressed in human platelets Gq, Gi2 and Gi3. Anti-Gq antibody, but not anti-Gi2 or Gi3 antibody, inhibited both GTP[S]- and GTP/U46619-dependent reconstitution of phosphoinositide hydrolysis with phospholipase C-beta. In contrast GTP[S]-stimulated hydrolysis by phospholipase C-delta was not inhibited by any of the G-protein antibodies. These results show the functional specificity of GTP-binding proteins and phospholipase C isoenzymes in mediating agonist-induced phosphoinositide hydrolysis in human platelets.

Increased phosphoinositide breakdown by phospholipase C in erythrocyte membranes from patients with cystic fibrosis

1989 ◽  
Vol 181 (1) ◽  
pp. 55-63 ◽  
Author(s):  
Claire Doughney ◽  
Margaret A. McPherson ◽  
Mary C. Goodchild ◽  
Robert L. Dormer
Keyword(s):  
Cystic Fibrosis ◽  
Phospholipase C ◽  
Erythrocyte Membranes ◽  
Phosphoinositide Breakdown

Inositol lipids and TRPC channel activation

2007 ◽  
Vol 74 ◽  
pp. 37-45 ◽  
Author(s):  
James W. Putney
Keyword(s):  
Plasma Membrane ◽  
Phospholipase C ◽  
Transient Receptor Potential ◽  
Calcium Signalling ◽  
Receptor Potential ◽  
Breakdown Product ◽  
Channel Activation ◽  
Inositol Lipids ◽  
Transient Receptor ◽  
Secondary Mechanism

The original hypothesis put forth by Bob Michell in his seminal 1975 review held that inositol lipid breakdown was involved in the activation of plasma membrane calcium channels or ‘gates’. Subsequently, it was demonstrated that while the interposition of inositol lipid breakdown upstream of calcium signalling was correct, it was predominantly the release of Ca2+ that was activated, through the formation of Ins(1,4,5)P3. Ca2+ entry across the plasma membrane involved a secondary mechanism signalled in an unknown manner by depletion of intracellular Ca2+ stores. In recent years, however, additional non-store-operated mechanisms for Ca2+ entry have emerged. In many instances, these pathways involve homologues of the Drosophila trp (transient receptor potential) gene. In mammalian systems there are seven members of the TRP superfamily, designated TRPC1–TRPC7, which appear to be reasonably close structural and functional homologues of Drosophila TRP. Although these channels can sometimes function as store-operated channels, in the majority of instances they function as channels more directly linked to phospholipase C activity. Three members of this family, TRPC3, 6 and 7, are activated by the phosphoinositide breakdown product, diacylglycerol. Two others, TRPC4 and 5, are also activated as a consequence of phospholipase C activity, although the precise substrate or product molecules involved are still unclear. Thus the TRPCs represent a family of ion channels that are directly activated by inositol lipid breakdown, confirming Bob Michell's original prediction 30 years ago.

Phospholipase C from Clostridium Perfringens Induces Human Platelet Aggregation in Plasma

1988 ◽  
Vol 59 (02) ◽  
pp. 236-239 ◽  
Author(s):  
Giovanna Barzaghi ◽  
Chiara Cerletti ◽  
Giovanni de Gaetano
Keyword(s):  
Platelet Aggregation ◽  
Receptor Antagonist ◽  
Phospholipase C ◽  
Clostridium Perfringens ◽  
Human Platelet ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Thromboxane Receptor Antagonist

SummaryWe studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37° C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAG) of PLC was 3-4 U/ml.We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoper- oxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.

Sign in / Sign up

Export Citation Format

Share Document