Inositol phosphate production in response to [Arg8]vasopressin, endothelin 1, and prostaglandin F2α in rat aorta and mesenteric arteries

1992 ◽  
Vol 70 (10) ◽  
pp. 1408-1416 ◽  
Author(s):  
Angèle Parent ◽  
Paul V. Nguyen ◽  
Xiao Ping Yang ◽  
Ernesto L. Schiffrin
Keyword(s):  
Phospholipase C ◽  
Blood Vessels ◽  
Time Course ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Prostaglandin F2α ◽  
Rat Aorta ◽  
Mesenteric Arteries ◽  
Phosphoinositide Metabolism ◽  
Endothelin 1

Vascular tissues such as rat aorta and mesenteric arteries are extensively used experimentally for the study of cardiovascular diseases. To further our understanding of the signal transduction mechanisms involved in responses to several potent vasoconstrictors, such as [Arg8]vasopressin (AVP), endothelin 1 (ET-1), and prostaglandin F2α (PGF2α), we have investigated the time course for production of inositol monophosphate (InsP1), bisphosphate (InsP2), and trisphosphate (InsP3) in response to these agonists as well as their relative potency for phosphatidylinositol hydrolysis. Time-course studies of production of the different inositol phosphates in response to AVP and PGF2α showed an early increase after 15–30 s of stimulation. Thereafter InsP3 declined towards baseline, with a secondary increase towards steady state after 5–10 min. Rapid turnover of InsP3 was reflected by accumulation of InsP1 and InsP2 in the presence of LiCl (20 mM) to inhibit monophosphatases. After 15–30 min of stimulation, there was accumulation of the Ins(1,3,4)P3 isomer. All three agonists induced greater accumulation of InsP2 in mesenteric arteries than in thoracic aorta, suggesting that turnover of Ins(1,4,5)P3 may be faster in the former than in the latter. The accumulation of total inositol phosphates induced by maximum concentrations of ET-1 was greater than in response to AVP or PGF2α. Dose–response curves showed that the rank order of potency for stimulation of production of inositol phosphates was AVP > ET-1 > PGF2α, similar to the sensitivity of blood vessels to these agents. Comparison of responses to ET-1 and ET-3 showed that the receptors stimulated by endothelins were of the isopeptide selective ETA subtype. In conclusion, all three agonists (AVP, ET-1, PGF2α) stimulate phospholipase C activity in rat aorta and in mesenteric arteries, although with different potencies. This study demonstrates that intact blood vessels allow a detailed investigation of inositol phosphate responses to different agonists of interest in cardiovascular research.Key words: phosphoinositide metabolism, phospholipase C, inositol trisphosphate, vasoconstrictors, blood vessels.

Rapid stimulation of Ins (1,4,5)P3 production in rat aorta by NE: correlation with contractile state

1993 ◽  
Vol 264 (1) ◽  
pp. H126-H132
Author(s):  
V. Pijuan ◽  
I. Sukholutskaya ◽  
W. G. Kerrick ◽  
M. Lam ◽  
C. van Breemen ◽  
...  
Keyword(s):  
Time Course ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Rat Aorta ◽  
Release Mechanism ◽  
Maximal Increase ◽  
Contractile State ◽  
Rapid Stimulation ◽  
Relationship Of ◽  
Stimulation Of

Rapid stimulation of Ins(1,4,5)P3 production in rat aorta by NE: correlation with contractile state. Am. J. Physiol. 264 (Heart Circ. Physiol. 33): H126-H132, 1993.--The isomeric composition of inositol phosphates generated in response to norepinephrine (NE) stimulation and the relationship of inositol phosphate production to release of intracellular Ca2+ as measured by contraction were characterized in rat aorta prelabeled with [3H]inositol. NE stimulated a rapid and transient increase in labeled D-myo-inositol 1,4,5-trisphosphate [Ins-(1,4,5)P3] levels. A maximal increase in labeled Ins(1,4,5)P3 occurred within 15 s of stimulation followed by a decline to control levels at 5 min. D-Myo-inositol 1,3,4-trisphosphate [Ins-(1,3,4)P3] and D-myo-inositol 1-monophosphate [Ins(1)P] levels also increased rapidly in response to NE. In contrast to the transient production of Ins(1,4,5)P3, Ins(1,3,4)P3 and Ins(1)P production was maintained in the presence of NE. Half-maximal stimulation of Ins(1,4,5)P3 production and Ca2+ release occurred at 0.3 microM NE, and maximal effects were obtained with 10 microM NE. The concentration-response curve and time course for production of Ins(1,4,5)P3 correlated with the neurotransmitter-induced Ca2+ release from intracellular stores, indicating that the level of Ins(1,4,5)P3 regulated the Ca(2+)-release mechanism. In the continued presence of NE, the intracellular pools did not completely refill with Ca2+ despite the return of Ins-(1,4,5)P3 levels to basal at 5 min. These results demonstrate that NE stimulates a rapid increase in Ins(1,4,5)P3 that correlates with contraction in Ca(2+)-free buffer. The reuptake of Ca2+ into intracellular stores is regulated by a mechanism that may not involve Ins(1,4,5)P3.

Augmented phosphoinositide metabolism in aortas from genetically hypertensive rats

1990 ◽  
Vol 258 (1) ◽  
pp. H173-H178 ◽  
Author(s):  
M. B. Turla ◽  
R. C. Webb
Keyword(s):  
Phospholipase C ◽  
Vascular Reactivity ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Receptor Activation ◽  
Phosphoinositide Hydrolysis ◽  
Phosphoinositide Metabolism ◽  
Hypertensive Rats ◽  
Wistar Kyoto

Recent studies suggest that serotonergic receptor activation is coupled to phospholipase C-mediated phosphoinositide hydrolysis, which results in the release of intracellular second messengers. The purpose of this study was to determine whether altered phosphoinositide metabolism is the basis for augmented vascular responsiveness to serotonin in genetic hypertension. Thoracic aortic segments isolated from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto normotensive rats (WKY) were labeled with myo-[3H]inositol and stimulated with serotonin in the presence of LiCl. Accumulation of [3H]inositol phosphates was then quantitated by column chromatography. Basal inositol phosphate accumulation and basal incorporation of myo-[3H]inositol into aortic cell membranes from SHRSP was not significantly different from WKY values. At 2.6 x 10(-7) to 2.6 x 10(-4) M serotonin, phosphoinositide metabolism was significantly augmented in aortae from SHRSP compared with WKY. Depolarization (100 mM KCl) did not increase phosphoinositide hydrolysis above basal levels in SHRSP or WKY. 2-Nitro-4-carboxyphenyl-N,N-diphenyl carbamate (NCDC), an inhibitor of phospholipase C, prevented the serotonin-induced phosphoinositide metabolism. NCDC also partially inhibited phasic contractions (responses in calcium-free solution) to serotonin in aortas from SHRSP and WKY. In conclusion, abnormal phosphoinositide metabolism may be one mechanism responsible for the characteristic increase in vascular reactivity to serotonin in hypertension.

scholarly journals Secretagogue-induced phosphoinositide metabolism in human leucocytes

1984 ◽  
Vol 222 (2) ◽  
pp. 307-314 ◽  
Author(s):  
R W Dougherty ◽  
P P Godfrey ◽  
P C Hoyle ◽  
J W Putney ◽  
R J Freer
Keyword(s):  
Phospholipase C ◽  
Lysosomal Enzyme ◽  
Time Course ◽  
Inositol Phosphates ◽  
Biological Response ◽  
Enzyme Secretion ◽  
Receptor Interaction ◽  
Polymorphonuclear Leucocytes ◽  
Phosphoinositide Metabolism ◽  
Binding Condition

The relationship between receptor binding of the formylated peptide chemoattractant formylmethionylleucylphenylalanine (fMet-Leu-Phe), lysosomal enzyme secretion and metabolism of membrane phospholipids was evaluated in both human polymorphonuclear leucocytes (PMN) and the dimethyl sulphoxide (Me2SO)-stimulated human myelomonocytic HL-60 leukaemic cell line. In both cell types, exposure to fMet-Leu-Phe (100 nM) induced rapid lysosomal enzyme secretion (maximal release less than 30 s) and marked changes in the 32P-labelling of the inositol lipids phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdIns4P), phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] as well as phosphatidic acid (PtdA). Specifically, levels of [32P]PtdIns and [32P]PtdIns(4,5)P2 decreased rapidly (peak decrease at 10-15s), with a subsequent increase at 30 s and later. PtdIns4P and PtdA showed only an increase. In Me2SO-differentiated HL-60 cells prelabelled with [3H]inositol for 20 h, fMet-Leu-Phe caused a net increase in the cellular content of [3H]inositol phosphates, including a rapid increase in [3H]inositol 1,4,5-trisphosphate, suggesting that PtdIns(4,5)P2 breakdown occurs by a phospholipase C mechanism. Both lysosomal enzyme secretion and changes in phospholipid metabolism occur over the same agonist concentration range with a similar time course. Binding of [3H]fMet-Leu-Phe, although occurring over the same concentration range, exhibited markedly slower kinetics. Although depletion of extracellular Ca2+ had no effect on ligand-induced polyphosphoinositide turnover, PtdIns turnover, PtdA labelling and lysosomal enzyme secretion were severely curtailed. These studies demonstrate a receptor-mediated enhancement of phospholipid turnover that correlates with a specific biological response to fMet-Leu-Phe. Further, the results are consistent with the idea that phospholipase C-mediated degradation of PtdIns(4,5)P2, which results in the formation of inositol trisphosphate, is an early step in the stimulus-secretion coupling pathway of the neutrophil. The lack of correlation between these two responses and the equilibrium-binding condition suggests that either these parameters are responsive to the rate of ligand-receptor interaction or only fractional occupation is required for a full biological response.

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.

scholarly journals Mobilization of extracellular Ca2+ by prostaglandin F2α can be modulated by fluoride in 3T3-L1 fibroblasts

1990 ◽  
Vol 272 (1) ◽  
pp. 167-174 ◽  
Author(s):  
M T Nakada ◽  
J M Stadel ◽  
S T Crooke
Keyword(s):  
Dose Response ◽  
Time Course ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Prostaglandin F2α ◽  
Prior Exposure ◽  
Common Mechanism ◽  
Fura 2 ◽  
Fluorescence Measurements ◽  
Subsequent Addition

Changes in the intracellular concentration of calcium [(Ca2+]i) have been shown to mediate the physiological effects of certain agonists. Ca2+ mobilization occurs through multiple mechanisms which involve both influx and internal release of Ca2+. Prostaglandin F2 alpha (PGF2 alpha) caused a transient mobilization of intracellular Ca2+ in 3T3-L1 fibroblasts. This effect was characterized by fluorescence measurements of trypsin-treated cells loaded with fura-2/AM. In the absence of extracellular Ca2+, the peak amount of Ca2+ mobilized by PGF2 alpha was decreased by 70%, a lag time before the onset of [Ca2+]i increase was observed, and the rate of rise of [Ca2+]i was slowed. Addition of NaF (10 mM) to fura-2-loaded 3T3-L1 cells caused a dose-dependent increase in [Ca2+]i after a brief (approximately 10 s) lag. Maximal effects (approximately 300 nM) were observed at 5-10 mM-NaF. This effect was dependent on the presence of extracellular Ca2+ and appeared to be independent of inositol phosphate production. After reaching a peak at around 40 s after fluoride addition, [Ca2+]i returned to near-baseline within 120 s. This return of [Ca2+]i to near-baseline after fluoride stimulation and the inability of the cells to respond to a subsequent addition of fluoride indicated that the response to fluoride underwent desensitization. Similarly, the pathway used by PGF2 alpha to mobilize Ca2+ underwent desensitization. Exposure of the cells to a maximally effective concentration of fluoride and subsequent addition of PGF2 alpha produced a [Ca2+]i response to PGF2 alpha which was similar in magnitude and kinetics to that seen for PGF2 alpha in the absence of extracellular Ca2+. Conversely, prior exposure of cells to PGF2 alpha diminished the ability of fluoride to mobilize Ca2+. PGF2 alpha also increased inositol phosphate formation, with a time course and dose-response consistent with its ability to increase [Ca2+]i. Prior exposure of cells to fluoride did not change the time course or dose-response characteristics of PGF2 alpha-induced generation of inositol phosphates. These data suggest that PGF2 alpha and fluoride share a common mechanism of activating Ca2+ influx in 3T3-L1 cells.

Signal transduction in rat myometrial cells: comparison of the actions of endothelin-1, oxytocin and prostaglandin F2α

1995 ◽  
Vol 133 (4) ◽  
pp. 467-474 ◽  
Author(s):  
Miklós Molnár ◽  
Frank Hertelendy
Keyword(s):  
Signal Transduction ◽  
Phospholipase C ◽  
Inositol Phosphate ◽  
Rank Order ◽  
Prostaglandin F2α ◽  
Intact Cells ◽  
Pregnant Rat ◽  
Endothelin 1 ◽  
Myometrial Cells ◽  
Prostaglandin F

Molnár M, Hertelendy F. Signal transduction in rat myometrial cells: comparison of the actions of endothelin-1, oxytocin and prostaglandin F2α. Eur J Endocrinol 1995;133:467–74. ISSN 0804–4643 The objectives of this study were to evaluate and compare the actions of endothelin-1 (ET-1), oxytocin, prostaglandin F2α (PGF2α) and inositol 1,4,5-trisphosphate (IP3) on Ca2+ mobilization in permeabilized rat myometrial cells and to examine the activation of the inositol lipid cycle in intact myocytes. Cells were isolated from late pregnant rat myometrium and used as confluent monolayers after a single passage. All four agonists caused a biphasic release of45Ca2+ from non-mitochondrial pool(s), with the rank order of potency: oxytocin > PGF2α > ET-1 > IP3. Inhibitors of phospholipase C blocked ET-1-and oxytocin-promoted but not PGF2α-promoted 45Ca2+ efflux. Similarly, heparin, an IP3 receptor blocker, failed to inhibit PGF2α-induced Ca2+ release while inhibiting the action of the other agonists. Endothelin-1 and oxytocin stimulated inositol phosphate accumulation at concentrations similar to those that promoted 45Ca2+ efflux, whereas about 100 times higher concentrations of PGF2α were needed to activate this signaling pathway in intact cells. It is concluded that the primary action of PGF2α in myometrial cells is to enhance Ca2+ influx, whereas oxytocin and ET-1 receptors are coupled to phospholipase C, generating IP3 and raising the intracellular concentration of free Ca2+ from intracellular as well as extracellular sources. Frank Hertelendy, Dept. Ob/Gyn, St Loufis University Health Sciences Center, 3635 Vista Ave at Grand Blvd, St Louis, MO 63110-0250, USA

IMPAIRMENT OF PLATELET PHOSPHOINOSITIDE METABOLISM IN PRIMARY HYPERTENSION

1987 ◽  
Author(s):  
S Koutouzov ◽  
A Remmal ◽  
P Marche ◽  
P Meyer
Keyword(s):  
Phospholipase C ◽  
Time Course ◽  
Blood Platelets ◽  
Second Messengers ◽  
Calcium Handling ◽  
Phosphoinositide Metabolism ◽  
Experimental Conditions ◽  
Spontaneously Hypertensive ◽  
Serotonin Secretion ◽  
Wistar Kyoto

Blood platelets from hypertensive patients and spontaneously hypertensive rats (SHR) display multiple abnormalities when compared with cells from normotensive controls. The major features of the modified platelet profile are an enhanced rate of adhesion/aggregation in response to many stimuli, a greater sensitivity for thrombin and adrenaline to produce increases in cytoplasmic free Ca2+, and an exaggerated release reaction. Furthermore, the resting levels of cytosolic free Ca2+ ions are specifically and constantly increased. Since phosphoinositides are involved in the stimulus-response coupling mediated by intracellular Ca2+ mobilization, the metabolism of these lipids was investigated in platelets of SHR and compared with those of normotensive Wistar-Kyoto rats (WKY). Following 32P-labelling of quiescent platelets, labeled lipids were analyzed both in platelets at rest and after thrombin stimulation. In resting platelets, the 32P associated with each of the phosphoinositides and phosphatidic acid (PA) was similar in SHR and WKY indicating that both the pool size of the various lipids and their basal turnover did not differ between the two strains. By contrast, within the first seconds after thrombin stimulation (10-60 sec), the dose-response and time-course curves of agonist-induced increase in 32P-PA were markedly shifted to the left and reached higher equilibrium levels in SHR. Since thrombin-induced 32P-PA formation is held as the most sensitive index of phospholipase C activity, our results indicate that this enzyme displays hyperreactivity in SHR (vs WKY). It is therefore likely that in SHR, the enhanced physiological responses (serotonin secretion, aggregation) that we observed under the same experimental conditions may be related to an increased formation of Phospholipase C products (inosi-toltriphosphate and diacylglycerol) which are the two second messengers responsible for internal Ca2+ mobilization and activation of protein kinase C, respectively. Therefore, these data suggest that the hypersensitivity of Phospholipase C may be involved in the overall alteration of cell calcium handling and hence in the SHR platelet responses.

scholarly journals Cyclic AMP agonists induce the phosphorylation of phospholipase C-τ and of a 76 kDa protein co-precipitated by anti-(phospholipase C-τ) monoclonal antibodies in BALB/c-3T3 cells. Relationship to inositol phosphate formation

1990 ◽  
Vol 272 (2) ◽  
pp. 297-303 ◽  
Author(s):  
N E Olashaw ◽  
S G Rhee ◽  
W J Pledger
Keyword(s):  
Monoclonal Antibodies ◽  
Growth Factor ◽  
Cyclic Amp ◽  
Phospholipase C ◽  
Cholera Toxin ◽  
Inositol Phosphate ◽  
Serine Phosphorylation ◽  
Intrinsic Activity ◽  
Phosphoinositide Metabolism ◽  
3T3 Cells

Previous studies have demonstrated enhanced phosphorylation of phospholipase C-tau (PLC-tau), a key regulatory enzyme in phosphoinositide metabolism, in cells treated with platelet-derived growth factor (PDGF) and epidermal growth factor, both of which act via specific receptor tyrosine kinases. Our studies on BALB/c-3T3 cells show that agents that promote cellular cyclic AMP accumulation also increase the phosphorylation, specifically the serine phosphorylation, of this enzyme. Increased phosphorylation of PLC-t (2-3-fold) was evident within 5-10 min of addition of isobutylmethylxanthine (IBMX) and either cholera toxin or forskolin to cells, and persisted for at least 3 h. Treatment of cells with cyclic AMP agonists also enhanced, with similar kinetics, the phosphorylation of a 76 kDa protein co-precipitated by anti-PLC-tau monoclonal antibodies. Brief exposure of cells to cholera toxin/IBMX or forskolin/IBMX decreased inositol phosphate formation induced by the GTP-binding protein (G-protein) activator aluminium fluoride by approx. 50%, but was without effect on PDGF-stimulated inositol phosphate formation. These findings suggest that PLC-tau, and perhaps the 76 kDa co-precipitated protein, are substrates of cyclic AMP-dependent protein kinase in BALB/c-3T3 cells: however, the lack of effect of cyclic AMP elevation on PDGF-stimulated inositol phosphate formation indicates that the intrinsic activity of PLC-tau is unaltered by cyclic AMP-mediated phosphorylation.

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.

scholarly journals Relationships between the degree of cross-linking of surface immunoglobulin and the associated inositol 1,4,5-trisphosphate and Ca2+ signals in human B cells

1992 ◽  
Vol 284 (2) ◽  
pp. 447-455 ◽  
Author(s):  
F M McConnell ◽  
S B Shears ◽  
P J L Lane ◽  
M S Scheibel ◽  
E A Clark
Keyword(s):  
B Cells ◽  
Tyrosine Kinase ◽  
Phospholipase C ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Cross Linking ◽  
Immunoglobulin Receptor ◽  
Surface Immunoglobulin ◽  
Human B Cells ◽  
Inositol 1,4,5 Trisphosphate

Cross-linking of surface immunoglobulin (Ig) receptors on human B cells leads to the activation of a tyrosine kinase. The activated tyrosine kinase subsequently phosphorylates a number of substrates, including phospholipase C-gamma. This enzyme breaks down phosphoinositol bisphosphate to form two intracellular messengers, diacylglycerol and inositol 1,4,5-trisphosphate, leading to the activation of protein kinase C and the release of intracellular Ca2+ respectively. We have used h.p.l.c. and flow cytometry to measure accurately the inositol phosphate turnover and Ca2+ release in anti-Ig-stimulated human B cells. In particular, we have examined the effect of dose of the cross-linking antibody on the two responses. The identity of putative messenger inositol phosphates has been verified by structural analysis, and the amounts of both inositol phosphates and Ca2+ present have been quantified. In the Ramos Burkitt lymphoma, which is very sensitive to stimulus through its Ig receptors, both inositol phosphate production and Ca2+ release were found to be related to the dose of anti-Ig antibody applied. This suggests that phospholipase C-mediated signal transduction in human B cells converts the degree of cross-linking of the immunoglobulin receptor quantitatively into intracellular signals.

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