Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The involvement of calcium in the release of tissue-type plasminogen activator (t-PA) and von Willebrand Factor (vWF) from vascular endothelial cells was studied ex vivo using a rat hindleg perfusion system. By adding either platelet-activating factor or bradykinin to the perfusing Tyrode solution, a rapid release of t-PA and vWF was induced. Extracellular calcium was required for the acute release of both glycoproteins as this release was totally abolished in the presence of EGTA. The calcium ionophore A-23187 induced (Ca-dependently) the release of both proteins, suggesting that Ca-influx was also sufficient to induce release. The absence of an effect of the calcium L-type channel blockers, verapamil and diltiazem, and of the calcium channel agonist BAY K-8644, suggested that endothelial voltage-operated calcium channels were not involved in release. Trifluoperazine, a calmodulin antagonist, significantly inhibited the induced release of t-PA and vWF, while the "intracellular calcium antagonist" TMB-8 had no effect. Lanthanum chloride (200 microM) inhibited the induced release of t-PA but not that of vWF. Our results suggest that Ca2+ influx is essential for the release of t-PA and vWF from the perfused rat hindleg.
 ...
PMID:On the role of calcium in the acute release of tissue-type plasminogen activator and von Willebrand factor from the rat perfused hindleg region. 172 76

Melittin, an activator of phospholipase (PL) A-2, increased the outputs of prostaglandin (PG) F-2 alpha and 6-keto-PGF-1 alpha, but not of PGE-2, from Day-7 guinea-pig uterus superfused in vitro. Reducing the extracellular calcium concentration (by omitting calcium chloride from the superfusing fluid) partially inhibited the stimulatory effect of melittin on uterine PG production. TMB-8 (an intracellular calcium antagonist) completely prevented the stimulation of PGF-2 alpha and 6-keto-PGF-1 alpha output by melittin, although the production of both PGs tended to increase after stopping the melittin and TMB-8 treatments. TMB-8 also inhibited the increases in outputs of PGF-2 alpha, 6-keto-PGF-1 alpha and PGE-2 and prevented contraction of the uterus induced by exogenous PLA-2. Trifluoperazine (a calmodulin antagonist) had no inhibitory effect on the increases in outputs of PGF-2 alpha and 6-keto-PGF-1 alpha produced by melittin; it potentiated the stimulatory effect of melittin on 6-keto-PGF-1 alpha output and allowed melittin to increase PGE-2 output. When melittin was applied twice to the superfused uterus with an interval of 1 h between each treatment, partial refractoriness of the responses to melittin was seen: the magnitudes of the increases in PGF-2 alpha and 6-keto-PGF-1 alpha outputs were 40-50% less after the second treatment than after the first treatment. These results show that melittin stimulates the synthesis of PGF-2 alpha and PGI-2 (measured as 6-keto-PGF-1 alpha) in guinea-pig uterus by mechanisms which are calcium dependent.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Effect of melittin on prostaglandin production by guinea-pig uterus. 178 78

Proteose peptone (p.peptone) remarkably induced tissue plasminogen activator (t-PA) activity in the conditioned medium of confluently cultured human embryonic lung diploid fibroblast, IMR-90 cells, in a dose-dependent manner. t-PA activity correlated well with the amount of t-PA antigen found in the conditioned medium of IMR-90 cells stimulated by p.peptone. t-PA production by IMR-90 cells stimulated by p.peptone was dependent on extracellular Ca2+ concentration and maximum t-PA production required approximately 3.6 mM extracellular Ca2+. Conversely, elimination of Ca2+ from the culture medium by EGTA, Ca2+ chelate agent, strongly inhibited t-PA production induced by p.peptone. t-PA production induced by p.peptone was inhibited in a dose-dependent manner by Verapamil, which inhibits Ca2+ uptake through the slow channels and also by W-7, an inhibitor of calmodulin. These results suggested that influx of extracellular Ca2+ into IMR-90 cells was caused by p.peptone and induced t-PA production by the cells.
 ...
PMID:Role of Ca2+ in t-PA production by human embryonic lung diploid fibroblast, IMR-90 cells, stimulated by proteose peptone. 190 95

Phorbol 12-myristate 13-acetate, 1-20 nM, induced the synthesis in HeLa cells of a 65 200 Mr tissue-type plasminogen activator, and of prostaglandin E2. Omission of Ca2+ from the incubation medium inhibited the induction of plasminogen activator synthesis by 40-60% and abolished the induction of prostaglandin E2 synthesis. Maximal plasminogen activator synthesis could be maintained at extracellular Ca2+ concentrations of approx. 0.1 mM, while maximal prostaglandin synthesis required at least 0.45-0.9 mM Ca2+. The induction of each factor was inhibited by 10-100 microM 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8), an inhibitor of intracellular C2+ mobilization. Prostaglandin synthesis, but not plasminogen activator synthesis, was also inhibited by 10-100 microM verapamil and nifedipine, which inhibit intracellular Ca2+ uptake via the so-called 'slow-channels' and by 0.5-10 microM trifluoperazine, an inhibitor of calmodulin. Neither plasminogen activator synthesis nor prostaglandin synthesis were stimulated by 5-50 microM 1-oleoyl-2-acetylglycerol or 1-250 microM 1,2-dioctanoylglycerol, alone and in combination with 50 nM-1 microM ionophore A23187. These results indicate that the synthesis of plasminogen activator and prostaglandins in HeLa cells is Ca2+-dependent, and that the Ca2+ requirements for each process are not identical. Thus, Ca2+ regulation of the production of tissue plasminogen activator and prostaglandin E2 occurs at multiple points in their biosynthetic pathways.
 ...
PMID:Calcium regulation of tissue plasminogen activator and prostaglandin biosynthesis in HeLa cells. 308 71

Spermatogenesis is dependent on stimulation by pituitary gonadotropins, FSH and LH. Targets for these hormones are Sertoli and Leydig cells, respectively. The effect of LH on spermatogenesis is mediated by testosterone. In addition to hormones, interactions between neighbouring cells seem to regulate spermatogenesis. This is reflected by cyclic secretion of several proteins by the seminiferous epithelium, of which plasminogen activator is a good example. While it is controlled by FSH a factor in preleptotene spermatocytes may also influence its cyclic secretion pattern. Both testosterone and FSH have a cyclic action in the seminiferous epithelium. The androgens seem to predominate in stages where spermiation, onset of meiosis and the highest rate of RNA transcription occur (VII-XI). FSH is most active in stages that contain meiotic divisions and early spermiogenesis (XIII-V), greatly stimulating the production of cyclic AMP. To investigate further the "second messengers" of FSH action in the seminiferous epithelium, the cellular distribution of calmodulin was analyzed using an indirect immunocytochemical method. In addition to their clear cyclic distribution in primary spermatocytes and in spermatids, Sertoli cells also showed a bright calmodulin immunofluorescence that was apparently cyclic. These observations suggest a local calmodulin and calcium regulation of spermatogenesis.
 ...
PMID:Cell interactions in the rat seminiferous epithelium with special reference to the cellular distribution of calmodulin. 308 86

In this study, we investigated the role of Ca2+ and G proteins in thrombin-induced acute release (regulated secretion) of tissue-type plasminogen activator (TPA) and von Willebrand factor (vWF), using a previously described system of primary human umbilical vein endothelial cells (HUVECs). The acute release of TPA and vWF, as induced by alpha-thrombin, was almost zero after chelation of Ca2+i, showing that an increase in [Ca2+]i was required. It did not matter whether the increase in [Ca2+]i came from an intracellular or extracellular Ca2+ source. Thrombin-induced release of TPA and vWF already started at low [Ca2+]i, around 100 nmol/L. Half-maximal release was found at a [Ca2+]i, of 261 nmol/L for TPA and at 222 nmol/L for vWF. The Ca2+ signal was transduced to calmodulin, as calmodulin inhibitors inhibited TPA and vWF release. The Ca2+ ionophore ionomycin dose dependently released vWF; half-maximal vWF release occurred at a [Ca2+]i of 311 nmol/L. In contrast, no TPA release was found at all below a [Ca2+]i of 500 nmol/L. Thus, below 500 nmol/L [Ca2+]i, an increase in [Ca2+]i alone was sufficient to induce vWF release but not sufficient to induce TPA release. Protein kinase C did not appear to be involved in TPA or vWF release, as neither an activator nor an inhibitor of protein kinase C significantly influenced release. Inhibition of phospholipase A2 also did not reduce thrombin-induced TPA and vWF release. The involvement of G proteins was studied by using both saponin-permeabilized and intact cells. GDP-beta-S, which inhibits heterotrimeric and small G proteins, significantly inhibited thrombin-induced vWF and TPA release from permeabilized cells. AlF-4, which activates heterotrimeric G proteins, induced TPA and vWF release in both intact and permeabilized HUVECs. Preincubation of HUVECs with pertussis toxin significantly inhibited thrombin-induced vWF release, due to inhibition of thrombin-induced Ca2+ influx. Pertussis toxin did not affect ionomycin-induced release. The inhibitory effect of pertussis toxin was less obvious in thrombin-induced TPA release, because it was counterbalanced by a positive effect of the toxin on TPA release. Thus, both inhibitory and stimulatory (pertussis toxin-sensitive) G proteins were involved in TPA release. Therefore, thrombin-induced acute release of TPA and vWF differed in two respects. First, below a [Ca2+]i of 500 nmol/L, an increase in Ca2+ was sufficient for vWF release but not for TPA release. Second, pertussis toxin-sensitive G proteins were differentially involved in acute TPA and vWF release.
 ...
PMID:Involvement of calcium and G proteins in the acute release of tissue-type plasminogen activator and von Willebrand factor from cultured human endothelial cells. 935 87

Nitric oxide (NO) is a multifunctional effector molecule that plays a central role in the regulation of vascular homeostasis. NO is synthesized from L-arginine by a family of enzymes called NO synthases. The principal source of NO in the vascular system of healthy mammals is the constitutively expressed NO synthase in endothelial cells. The basal endothelial formation of NO can be increased by receptor-dependent agonists (i.e., bradykinin) in a calcium-calmodulin-dependent manner, and also by physical forces (i.e., shear stress), predominantly without changes in the intracellular concentration of free calcium. Nitric oxide can diffuse toward the blood vessel wall where the major target is the smooth muscle cell. NO regulates vascular tone, and the free radical is also a potent inhibitor of smooth muscle cell proliferation, migration and synthesis of extracellular matrix proteins. NO can also diffuse toward the lumen of the blood vessel where it helps maintain blood fluidity. NO inhibits platelets' and leucocytes' adhesion to endothelial cells. In addition, NO inhibits platelet aggregation and facilitates the dissolution of small platelet aggregates. However, the regulatory action of NO on blood cells is most likely limited to the luminal surface of endothelial cells since NO is rapidly scavenged by hemoglobin in erythrocytes and inactivated by oxygen-derived radicals such as superoxide anions. NO can also affect the fibrinolytic activity by regulating the release of tissue-type plasminogen activator and plasminogen activator inhibitor-1. The crucial role of vascular NO in the control of blood fluidity has been demonstrated by the regulation of the bleeding time in humans.
 ...
PMID:Vascular biosynthesis of nitric oxide: effect on hemostasis and fibrinolysis. 1066 93

We investigated the effect of phospholipase A(2) (PLA(2)) inhibitors on PLA(2) activity and cell viability in cold-stored rat hepatocytes. The cells were radiolabeled with [(3)H] arachidonic acid (AA) and cold stored in the University of Wisconsin (UW) solution containing various PLA(2) inhibitors. PLA(2) activity was determined by measuring the total free (cellular + supernatant) AA by thin-layer chromatography after inhibiting reacylation of free AA with inhibitors of energy production (carbonyl cyanide m-chlorophenylhydrazone + iodoacetate). Aristolochic acid, chlorpromazine, and quinacrine in the UW solution showed a significant inhibitory effect throughout 48 h cold storage but only at relatively high concentration. PLA(2) activity was also suppressed (58% of control) by trifluoperazine (50 microM), but its effect was limited to only 24 h. In contrast, pretreatment of the cells prior to hypothermic preservation with trifluoperazine (10 to 100 microM) suppressed PLA(2) activity during 48 h storage. Inclusion of calmodulin antagonist W-7 did not affect PLA(2) activity. Thus, the inhibitory activity of these agents appears unrelated to Ca-calmodulin-phospholipid interaction but to have an inhibitory effect on PLA(2) activity. To study the effects of PLA(2) inhibitors on cell viability, lactate dehydrogenase (LDH) release was measured in the presence or absence of inhibitors upon rewarming cold-stored cells in Krebs-Henseleit buffer for 2 h at 37 degrees C. None of the inhibitors tested improved cell viability after 48 h storage. Thus, although PLA(2) inhibitors blocked PLA(2) activity, there was no suppression of LDH release. PLA(2) may play a minor role in preservation/reperfusion injury to cold-stored hepatocytes.
 ...
PMID:Effect of phospholipase A2 inhibitors on the release of arachidonic acid and cell viability in cold-stored hepatocytes. 1067 47

We have previously demonstrated that Ca(2+)/calmodulin-dependent protein kinase (CaMK) mediates pyrimidinoceptor potentiation of LPS-elicited inducible nitric oxide synthase (iNOS) induction in murine J774 macrophages. In the present paper, we have explored the role of cyclo-oxygenase (COX)-dependent prostaglandin E(2) (PGE(2)) formation in this event. In J774 macrophages predominantly expressing P2Y(6) receptors, the simultaneous addition of UTP and lipopolysaccharide (LPS) resulted in potentiated increase in PGE(2) release. UTP-induced increased PGE(2) release was demonstrated by a concomitant increase in COX-2 protein expression, and was decreased by inhibitors specific for phosphatidylinositide-phospholipase C (PI-PLC), CaMK, protein kinase C (PKC), nuclear factor-kappa B (NF-kappaB) or COX-2. NS-398 (a selective COX-2 inhibitor) reduced LPS plus UTP-elicited iNOS induction and nitrite accumulation, supporting for the positive regulation of iNOS gene expression by endogenous PGE(2). Moreover, the cyclic AMP/PKA-dependent up-regulation of iNOS expression mediated by PGE(2) was drawn from the inhibitory effects of 2',5'-dideoxyadenosine, KT5720 and H-89. Exogenous PGE(2) induced NF-kappaB activation and potentiated nitrite accumulation in response to LPS. In addition to COX-2 induction, arachidonic acid (AA) release and steady-state mRNA levels of type V secretory phospholipase A(2) (sPLA(2)) and Ca(2+)-independent PLA(2) (iPLA(2)) were also increased in the presence of LPS and UTP; the LPS-induced increase in iPLA(2) activity was also potentiated by UTP. Taken together, we conclude that UTP-mediated COX-2 and iPLA(2) potentiation and PGE(2) formation contribute to the iNOS induction, and that CaMK activation is the primary step in the UTP enhancement of COX-2 induction.
 ...
PMID:Pyrimidinoceptor potentiation of macrophage PGE(2) release involved in the induction of nitric oxide synthase. 1086 83

Several lines of evidence indicate that phospholipase A(2) (PLA(2)) plays a crucial role in plant cellular responses through production of linolenic acid, the precursor of jasmonic acid, from membrane phospholipids. Here we report the purification and characterization of a 48-kD PLA(2) from the membrane fractions of leaves of broad bean (Vicia faba). The plant PLA(2) was purified to near homogeneity by sequential column chromatographies from the membrane extracts. The purified 48-kD protein migrated as a single band on a SDS-PAGE gel and its density correlated with the PLA(2) activity. It was further confirmed that this 48-kD protein is the PLA(2) enzyme based on immunoprecipitating the activity with a monoclonal antibody against it and purifying the enzyme to homogeneity with the antibody affinity column. The purified plant PLA(2) preferred 2-linolenoyl-sn-glycerol-3-phosphocholine (GPC) to 2-linoleoyl-GPC, 2-palmitoyl-GPC and 2-arachidonyl-GPC as substrates with a pH optimum at pH 7.0 to 8.0. The plant PLA(2) was activated by calmodulin and inhibited by pretreatment of 5,8,11, 14-eicosatetraynoic acid known as an inhibitor of mammalian PLA(2)s. The enzyme was characterized as a Ca(2+)-independent PLA(2) different from mammalian PLA(2)s. This membrane-associated and Ca(2+)-independent PLA(2) is suggested to play an important role in the release of linolenic acid, the precursor of jasmonic acid, through a signal transduction pathway.
 ...
PMID:Purification and characterization of a membrane-associated 48-kilodalton phospholipase A(2) in leaves of broad bean. 1088 55


1 2 3 Next >>