Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The specific binding of 3H-labeled prostaglandin (PG) F2alpha to bovine corpus luteum cell membranes was a rapid (K1=1.1 X 10(4) M(-1)S(-1) and reversible (K(-1)=3.3 X 10(-4) S(-1)) process at 22 degrees C. The specific binding was also a saturable process exhibiting two classes of receptors with apparent dissociation constants (Kds) of 1.6 X 10(-9) M and 2.4 X 10(-8) M. The heterogenous nature of [3H]PGF2alpha binding does not appear to be due to negative cooperatively but merely to represent the existence of two independent groups of receptor sites with discrete affinities. Free energy changes of +11.9 and +10.3 Kcal/mol were calculated from the Kds of high and low affinity receptors, respectively. The binding of [3H]PGF2alpha to the membranes was not accompanied by any detectable changes in receptor-bound or free [3H]PGF2alpha. Addition of increasing amounts of unlabeled PGF2alpha resulted in a dose-dependent inhibition of [3H]PGF2alpha binding to the membranes, with complete inhibition occurring at 10(-6) M. Other unlabeled PGs such as PGF1alpha, PGE2 (5-fold), PGE1 (120-fold), PGA1 and PGB1 (about 10,000-fold) were less effective when compared to unlabeled PGF2alpha in inhibiting [3H] PGF2alpha binding to the membranes. The metabolites of PGF2alpha, 15-keto-PGF2alpha and 13,14-dihydro-15-keto-PGF2alpha had 100-fold less affinity for PGF2alpha receptors. 15(S)15-Methyl-PGF2alpha, an analogue of PGF2alpha, had a fairly high affinity but lower than its parent molecule. Various unsaturated fatty acids, indomethacin and 7-oxa-13-prostynoic acid had 3,000- to 10,000-fold less affinities for PGF2alpha receptors. Incubation of membranes with various enzymes revealed that PGF2alpha receptor molecules are protein in nature which require membrane lipids and specific phospholipids for binding function. Among the various phospholipids used, sphingomyelin was found to be very effective in restoring the loss of [3H]PGF2alpha binding in phospholipase C-treated membranes. N-Ethylmaleimide, but not other SH group alkylating agents inhibited binding. The binding was also inhibited by tetranitromethane, dinitrofluorobenzene and acetic anhydride. This suggested that tyrosyl, histidyl, tryptophan and amino (any one or all of them) but not SH groups were involved in binding interaction.
...
PMID:Properties of prostaglandin F2alpha receptors in bovine corpus luteum cell membranes. 1 62

Renin-angiotensin (RA) system plays an important role in cardiovascular homeostasis. Here, we have described the recent progress in our study of renin release as well as the cellular action of angiotensin II. (1) Microdissection of an isolated afferent artery with or without macula densa (MD) has revealed that renin release is regulated by NaCl exposure to MD. Furosemide, prostaglandins (PGE2 and PGI2) and adenosine modulate its function. (2) Angiotensin (ang) II increases cytosolic free calcium and induces the formation of inositolphosphates in vascular smooth muscle cells. Deduced protein structure of ang II receptor (AT1-R) cDNA has indicated the presumed link of AT1-R with phospholipase C. Through the cellular action, ang II has been reported to regulate gene expression.
...
PMID:[Mechanism of renin release and cellular action of angiotensin II]. 129 35

We investigated the effects of an exogenous Type I phospholipase C (PLC) from clostridium perfringens on arachidonic acid release and prostaglandin synthesis from gastric mucosa by determining PGE2 release from organ cultured rabbit mucosal biopsies as well as PGE2 synthesis and substrate-dependent inactivation of the prostaglandin cyclooxygenase from endogenously released arachidonic acid in mucosal homogenate. PLC dose dependently stimulated PGE2 secretion from organ cultured mucosa to 145% and 245% at 0.1 and 1.0 U/ml during a 60 minute culture period. This effect was not affected by the calmodulin antagonist N-(6-aminohexyl)-1-5-chloro-1-naphthalene-sulfonamide (W-7) or the intracellular calcium chelator 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N',-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). PLC could not be substituted by phorbol-12-myristate 13-acetate (PMA), an analogue of the diacylglycerol second messenger functions. During a 15 minute preincubation of mucosal homogenate at 37 degrees C, 1mM CaCl2 stimulated PGE2 synthesis from endogenous arachidonic acid about 5-fold compared to an EDTA-control. In contrast, the residual prostaglandin synthesizing capacity, determined by incubation with excess 14C-labelled arachidonic acid, was reduced by CaCl2 to 37% of the EDTA-value. Quinacrine, an inhibitor of arachidonic acid release from phosphatidylethanolamine, reduced both the stimulation of PGE2 synthesis and the inactivation of prostaglandin cyclooxygenase. Therefore we conclude, that this Ca(2+)-effect reflects activation of the Ca-dependent phospholipase A2 (PLA2) and, as a consequence, substrate-induced inactivation of the prostaglandin cyclooxygenase.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Activation of PGE2-secretion from gastric mucosa by a type I phospholipase C is mediated by a direct release of arachidonic acid. 130 34

The relationship between calcium mobilization and phospholipase D (PLD) activation in response to E-series prostaglandins (PGEs) was investigated in human erythroleukemia cells. Intracellular free Ca2+ concentration ([Ca2+]i) was increased by PGE1 and PGE2 over the same concentration range at which PLD activation was seen. Pretreatment of cells with pertussis toxin greatly inhibited the PGE-stimulated increase in [Ca2+]i, implying that a G protein participates in the PGE receptor signaling process. The peak level and also the plateau level of Ca2+ mobilization stimulated by these prostaglandins were markedly decreased in Ca(2+)-depleted medium, indicating that both extracellular and intracellular Ca2+ stores contribute to the changes in [Ca2+]i. Likewise, activation of PLD by PGE1 and PGE2 was abolished by pertussis toxin pretreatment or incubation in Ca(2+)-depleted medium. U73122, a putative phospholipase C inhibitor, blocked both Ca2+ mobilization and PLD activation in PGE-stimulated cells. Furthermore, the intracellular loading of BAPTA, a Ca2+ chelator, inhibited both Ca2+ mobilization and PLD activation by PGE1 and PGE2 in a similar dose-dependent manner. Simultaneous measurement of [Ca2+]i and PLD activity in the same cell samples indicated that PLD activity increases as a function of [Ca2+]i in a similar fashion in cells stimulated either by PGEs or by the calcium ionophore ionomycin. Taken together, these findings suggest that a rise in [Ca2+]i is necessary for PGE-stimulated PLD activity in human erythroleukemia cells.
...
PMID:Direct relationship between intracellular calcium mobilization and phospholipase D activation in prostaglandin E-stimulated human erythroleukemia cells. 131 95

PGD2 stimulated DNA synthesis and decreased alkaline phosphatase activity dose-dependently between 10 nM and 10 microM in osteoblast-like MC3T3-E1 cells. PGD2 had little effect on cAMP production, but caused very rapid enhancement of phosphoinositide (PI) hydrolysis dose-dependently between 10 nM and 10 microM. The formation of inositol trisphosphate (IP3) induced by PGD2 reached the peak within 1 min and decreased thereafter, which is more rapid than that induced by PGE2 or PGF2 alpha and both PGE2 and PGF2 alpha affected PGD2-induced IP3 formation additively. Pertussis toxin (PTX) inhibited both PGD2-induced formation of inositol phosphates and DNA synthesis. The degree of these PTX (1 micrograms/ml)-induced inhibitions was similar. In addition, neomycin, a phospholipase C inhibitor, inhibited PGD2-induced DNA synthesis as well as the formation of IP3, and the patterns of both inhibitions were similar. In the cell membranes, PTX-catalyzed ADP-ribosylation of a 40-kDa protein was significantly attenuated by pretreatment of PGD2. Time course of the attenuation of PTX-catalyzed ADP-ribosylation by PGD2 was apparently different from that by PGE2 or PGF2 alpha. These results indicate that PGD2 activates PTX-sensitive GTP-binding protein independently from PGE2 or PGF2 alpha and stimulates PI hydrolysis resulting in proliferation of osteoblast-like cells.
...
PMID:Proliferative effect of PGD2 on osteoblast-like cells; independent activation of pertussis toxin-sensitive GTP-binding protein from PGE2 or PGF2 alpha. 131 47

We examined the effect of estradiol on PGE2-induced phosphoinositide hydrolysis and cAMP production in cloned osteoblast-like MC3T3-E1 cells. 17 beta -Estradiol pretreatment significantly inhibited the formation of inositol phosphates induced by 10 microM PGE2 in a dose-dependent manner between 1 pM and 10 nM. This effect of 17 beta -estradiol was dependent on the time of pretreatment and submaximum inhibition was observed at 4 h. However, 17 beta -estradiol had little effect on the formation of inositol phosphates induced by 20 mM NaF, a GTP-binding protein activator. The cAMP production induced by PGE2 was not influenced by 17 beta -estradiol. These results suggest that 17 beta -estradiol modulates the signal transduction by PGE2 and that the effect seems to be exerted between PGE2 receptor and the GTP-binding protein coupled to phospholipase C in osteoblast-like MC3T3-E1 cells.
...
PMID:Inhibitory effect of 17 beta -estradiol on prostaglandin E2-induced phosphoinositide hydrolysis in osteoblast-like cells. 132 66

We have previously reported that platelet-activating factor (PAF) elevates cytosolic free calcium concentration ([Ca2+]i) in fura-2-loaded glomerular mesangial cells. To confirm that this increase in [Ca2+]i is a result of receptor-mediated activation of phospholipase C, we investigated hydrolysis of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P2) in PAF-treated mesangial cells. PAF (10(-7) M) stimulated a rapid and transient formation of inositol trisphosphate. In concomitant experiments, PAF stimulated a biphasic accumulation of 3H-arachidonate-labeled 1,2-diacylglycerol (DAG). The secondary elevation in DAG was coincident with a rise in 3H-phosphorylcholine (PC) and 3H-phosphorylethanolamine (PE) suggesting that PAF stimulates delayed phospholipase activities which hydrolyze alternate phospholipids besides the polyphosphoinositides. This PAF-stimulated elevation in 3H-water soluble phosphorylbases was seen at 5 min but not at 15 sec suggesting that the initial rise in DAG as well as the initial elevation in [Ca2+]i are due primarily to PtdIns-4,5-P2 hydrolysis. PAF also stimulated PGE2 as well as 3H-arachidonic acid and 3H-lyso phosphatidylcholine (PtdCho) formation. We suggest that arachidonate released specifically from PtdCho via phospholipase A2 is a source of this PAF-elevated PGE2. It has been postulated that anti-inflammatory prostaglandins may antagonize the contractile and proinflammatory effects of PAF via activation of adenylate cyclase. Surprisingly, exogenous PAF reduced basal and receptor-mediated cAMP concentration indicating that PAF-stimulated transmembrane signaling pathways may oppose receptor-mediated activation of adenylyl cyclase. We have taken advantage of the different sensitivities of phospholipases A2 and C(s) to PMA, EGTA, and pertussis toxin to dissociate phospholipase A2 and C activities. Acute PMA-treatment enhanced PAF-stimulated PGE2 formation, reduced PAF-induced elevations in [Ca2+]i and had no effect upon PAF-stimulated 3H-PE. We have also demonstrated that phospholipase A2, but not PtdIns-specific phospholipase C, was sensitive to external calcium concentration. The role of a GTP-binding protein to couple PAF-receptors to the PtdIns-specific phospholipase C was confirmed as GTP gamma S synergistically elevated PAF-stimulated inositol phosphate formation. We also demonstrated that pertussis toxin ADP-ribosylates a single protein of an apparent 42 kD mass and that PAF pretreatment reduced subsequent ADP-ribosylation in a time-dependent manner. However, pertussis toxin had no effect upon phospholipase C-generated water soluble phosphorylbases or inositol phosphates. In contrast, PAF-stimulated phospholipase A2 and PAF-inhibited adenylyl cyclase activities were sensitive to pertussis toxin.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Platelet-activating factor stimulates multiple signaling pathways in cultured rat mesangial cells. 133 Nov 21

The glomerular mesangial cell is a specialized pericyte with multiple functional capabilities including contraction. Mesangial contraction may reduce the glomerular filtration surface area and hence the ultrafiltration coefficient, Kf. Cultured mesangial cells convert arachidonic acid into biologically active eicosanoids which are either contractile (thromboxane A2 [TxA2], prostaglandin F2 alpha [PGE2 alpha]) or relaxant (PGE2, PGI2). The addition of TxA2 analogues, PGE2 or sulfidopeptide leukotrienes (LTC4 and LTD4) stimulated contraction of cultured mesangial cells with threshold responses at approximately 1 nM and maximum responses at 1 microM. PGE2 and PGI2 antagonized mesangial contraction induced by TxA2 analogues. Contraction was enhanced by inhibiting mesangial cyclooxygenase with nonsteroidal antiinflammatory drugs (NSAID). Contractile eicosanoids stimulated phospholipase C thereby elevating intracellular inositol trisphosphate and cytosolic free Ca2+ concentration ([Ca2+]i). Vasorelaxant prostanoids stimulated adenylate cyclase, increasing intracellular cyclic AMP. We conclude that eicosanoids control mesangial contractility by regulating [Ca2+]i and cAMP. NSAID increase mesangial reactivity by blocking the inhibitory effects of endogenous vasodilator eicosanoids, with potential consequences on glomerular hemodynamics.
...
PMID:Eicosanoids, mesangial contraction, and intracellular signal transduction. 141 47

Attempts were made to identify prostaglandin (PG) receptors in rat myometrium, according to the differential rank order of potencies displayed by the natural PGs and their analogues, both at the level of second messenger generation and contraction. In estrogen-treated rat myometrium, PGs [iloprost = PGI2 greater than PGE2 much greater than 16,16-dimethyl (DM)-PGE2; sulprostone = misoprostol = 0] induced adenosine 3',5'-cyclic monophosphate generation, indicating the contribution of a PGI2 receptor. The generation of inositol phosphates was stimulated by PGs (PGF2 alpha greater than PGD2 much greater than PGE2 = DM-PGE2 much greater than iloprost greater than sulprostone = misoprostol = 0), reflecting a PGF2 alpha-receptor-mediated process, which was insensitive to pertussis toxin (PTX). Contractions caused by PGF2 alpha were closely correlated to PGF2 alpha-receptor activation associated with the phospholipase C pathway. By contrast, contractions evoked by PGE2, equally mimicked by sulprostone and misoprostol, were abolished by PTX and were independent of phospholipase C activation. In the pregnant myometrium (day 21), the latter PGE-receptor-mediated mechanism also contributed to contractions caused by PGE2 (less than microM concn). Phospholipase C activation was coupled not only to PGF2 alpha but also to PGE receptors and could be correlated with contractions induced by PGF2 alpha and PGE2 greater than microM concn). All PGs tested were coupled to inhibitory G protein-mediated adenylate cyclase inhibition, displaying an equipotency that did not allow characterization of the inhibitory PG receptors.
...
PMID:Diverse prostaglandin receptors activate distinct signal transduction pathways in rat myometrium. 163 81

In this report, we describe a Jurkat cell variant, termed JCT8, the selection of which is based upon its resistance to cell-growth inhibition mediated by the holotoxin of Vibrio cholerae, cholera toxin (CT). JCT8 cells exhibit normal cAMP production in response to various cAMP inducers, including CT, together with conserved ADP ribosylation in vitro of G-protein Gs alpha by the A subunit of the toxin. However, after a 4-h pretreatment with CT, JCT8 cells have a conserved expression of cell-surface CD3 molecules. These effects are in contrast to those elicited by the toxin in long term PGE2-desensitized Jurkat cells, which remain as sensitive as the wild type to the inhibitory action of CT on cell growth and CD3 cell-surface expression, despite poor responsiveness to CT with regard to cAMP production. In JCT8 cells, Ca2+ mobilization induced via the CD3/TCR is maintained after CT treatment contrasting with its complete suppression in the wild-type and in the PGE2-desensitized cells. However, as in the other cell types, CT still suppresses Ca2+ influx in JCT8 cells. Increase in inositol phosphates by CD3 stimulation of JCT8 cells, including of inositol 1,4,5-triphosphate (I(1,4,5)P3), is only partially antagonized by CT. This suggests either that in JCT8 cells there is a different susceptibility of Ca2+ mobilization and influx to partial inhibition by CT of CD3-triggered phospholipase C (PLC)-induced phosphoinositide hydrolysis or that an additional and PLC-independent suppressive effect of the toxin on Ca2+ influx may exist. To investigate this particular point further, we use Thapsigargin, a Ca(2+)-endoplasmic reticulum ATPase inhibitor that can mobilize in human T lymphocytes I(1,4,5)P3-dependent intracellular Ca2+ pools by a PLC-independent pathway. We demonstrate that the Ca2+ influx triggered in the wild-type Jurkat cells or in JCT8 cells by Thapsigargin is antagonized by CT. The present data are therefore consistent with the idea that CT specifically impairs in the Jurkat T cell model the entry of Ca2+ from extracellular spaces by a mechanism independent not only from cAMP but also in part from inhibition by the toxin of phosphoinositide hydrolysis.
...
PMID:Cyclic AMP- and inositol phosphate-independent inhibition of Ca2+ influx by cholera toxin in CD3-stimulated Jurkat T cells. A study with a cholera toxin-resistant cell variant and the Ca2+ endoplasmic reticulum-ATPase inhibitor thapsigargin. 165 Mar 86


1 2 3 4 5 6 7 8 9 10 Next >>

---