Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lipocortin I, in some cells, may be a potent inhibitor of phospholipase A2 activity. These studies evaluated the relative amounts of lipocortin I in human alveolar macrophages compared with blood monocytes, using a specific polyclonal antibody and the technique of Western analysis. Lipocortin I was detected in all isolates of human alveolar macrophages and had molecular masses of 37,000 and 33,000 D. Corticosteroids increased amounts of lipocortin I in these cells in a dose-dependent manner. This effect was specific for corticosteroids as related steroids had no effect. Blood monocytes, when compared with alveolar macrophages, contained relatively small amounts of lipocortin I. We conclude that lipocortin I is present in relatively large amounts in human alveolar macrophages and that amounts of the protein can be induced by corticosteroids. We further speculate that the relative amounts of lipocortin I within monocytes/macrophages may be a marker of differentiation.
Am J Respir Cell Mol Biol 1992 Jan
PMID:Lipocortin I production by human alveolar macrophages. 153 Aug 12

The present study specifically addresses the role of protein kinase C (PKC) activation in human endothelial cell Ca2+ mobilization, a response that is functionally coupled to the production of the potent arachidonate (AA) metabolite, prostacyclin (PGI2). Phorbol 12-myristate 13-acetate (PMA), alpha-thrombin, and sodium fluoride (NaF), a direct G-protein activator, produced a rapid and time-dependent translocation of PKC from the cytosol to the membrane. Activation of PKC by brief pretreatment of human umbilical vein endothelial cell (HUVEC) monolayers with PMA resulted in the inhibition of NaF-induced inositol phosphate increases and attenuation of both alpha-thrombin- and NaF-activated increases in intracellular Ca2+ (Ca2+i). Ca2+ mobilization induced by ionophore A23187 was not affected by PKC preactivation, suggesting PKC-dependent negative feedback inhibition of phosphatidylinositol (PI)-specific phospholipase C (PLC). Agonist-stimulated AA release and PGI2 synthesis in PMA-pretreated cultured human endothelial cells, however, was potentiated, and the enhanced PGI2 synthesis produced by A23187, NaF, and alpha-thrombin was dependent upon the dose of PMA. Treatment of HUVEC monolayers with an intracellular Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N'N'-tetraacetic acid-acetoxymethylester (BAPTA-AM), dramatically reduced alpha-thrombin-, NaF-, and A23187-induced PGI2 synthesis, demonstrating the importance of Ca2+i availability in PGI2 synthesis. BAPTA pretreatment did not inhibit PMA-induced PKC activation, and BAPTA-mediated inhibition of agonist-stimulated PGI2 synthesis was partially attenuated by prior PMA pretreatment. Staurosporine, a potent PKC inhibitor, at concentrations that inhibited PKC-induced phosphorylation of histone-1, augmented both alpha-thrombin- and NaF-induced production of inositol phosphates but markedly inhibited alpha-thrombin-, NaF-, and A23187-induced PGI2 synthesis. The downregulation of PKC activity by prolonged PMA treatment (18 h) produced similar inhibition of PGI2 synthesis by these agonists (approximately 50% inhibition). These studies indicate that the integrated phospholipase A2 and PLC activities are under complex regulation by factors that include both PKC activation and [Ca2+i]. PKC exerts dual effects on prostaglandin synthesis via negative regulation of Gp-coupled PI-specific PLC and positive feedback regulation of AA release and PGI2 synthesis. PKC is thus a critical determinant in the regulation of human endothelial cell prostaglandin synthesis by both receptor-mediated and G-protein-dependent cellular activation.
Am J Respir Cell Mol Biol 1992 Mar
PMID:Role of protein kinase C in the regulation of prostaglandin synthesis in human endothelium. 154 Mar 95

The rat Clara cell 17 kDa protein (previously referred to as the rat Clara cell 10 kDa protein) has been reported to inhibit phospholipase A2 and papain, and to also bind progesterone. It has been isolated from rat lung lavage fluid and crystallized in the space group P6(5)22. The structure has been determined to 3.0 A resolution using the molecular replacement method. Uteroglobin, whose amino acid sequence is 55.7% identical, was used as the search model. The structure was then refined using restrained least-squares and simulated annealing methods. The R-factor is 22.5%. The protein is a covalently bound dimer. Two disulfide bonds join the monomers together in an antiparallel manner such that the dimer encloses a large internal hydrophobic cavity. The hydrophobic cavity is large enough to serve as the progesterone binding site, but access to the cavity is limited. Each monomer is composed of four alpha-helices. The main-chain structure of the Clara cell protein closely resembles that of uteroglobin, but the nature of many of the exposed side-chains differ. This is true, particularly in a hypervariable region between residues 23 and 36, and in the H1H4 pocket.
J Mol Biol 1992 Mar 20
PMID:Refined structure of rat Clara cell 17 kDa protein at 3.0 A resolution. 156 Apr 60

We describe some properties on an Mr 30,000 thermolabile and trypsin-sensitive protein that activates phospholipase A2 (PLA2) and which was isolated from nervous tissue of the marine mollusk, Aplysia californica. A similar protein is present in rat cerebral cortex. This protein was partially purified from crude homogenates of nervous tissue by ion exchange chromatography on DEAE-Sephadex followed by size-exclusion high performance liquid chromatography (HPLC). It is loosely associated with membrane fractions, and is extracted by 0.05% Tween 20. Although similar in size to several previously described PLA2-stimulating proteins from non-neural mammalian cells and tissues, it differs from them in some aspects of biological activity. The protein promotes the release of eicosanoids from the membranes of intact Aplysia neurons prelabeled with [3H]arachidonic acid and appears to be an in vitro substrate for protein kinase C (PKC). PLA2-stimulating activity is greatly enhanced after exposing isolated ganglia to phorbol dibutyrate (PDBu) and is reduced by treatment with immobilized E. coli alkaline phosphatase. These observations suggest that phosphorylation of this stimulatory protein by PKC regulates PLA2 in neurons.
Brain Res Mol Brain Res 1991 Mar
PMID:A phospholipase A2-stimulating protein regulated by protein kinase C in Aplysia neurons. 164 37

Incubation of rocker-cultured neonatal rat heart cells with 3 mM L(+)-lactate led to a sharp increase in the sensitivity of cardiomyocytes to the beta-adrenergic agonist isoprenaline, as measured by their chronotropic response. This effect was accompanied by a reduction in the arachidonic acid content of the total phospholipids. The phospholipase A2-activator melittin as well as free arachidonic acid induced this supersensitivity to the same degree. On the other hand, the L(+)-lactate-evoked supersensitivity could be blocked by the phospholipase A2 inhibitors mepacrine and n-bromophenacyl-bromide, suggesting an involvement of phospholipase A2 in the process of beta-adrenergic sensitization. The sensitizing action of arachidonic acid was blocked by the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid, but not by the cyclo-oxygenase inhibitor indomethacin. Supersensitivity was likewise evoked by 15-S-hydroxyeicosatetraenoic acid (15-S-HETE), but not by 5-S-HPETE or 5-S-HETE. These findings suggest that the phospholipase A2-15-lipoxygenase pathway plays a role in the induction of beta-adrenergic supersensitivity in the cultured cardiomyocytes and point to a new physiological role of the lipoxygenase product 15-S-HETE.
Mol Cell Biochem 1991 Mar 27
PMID:Modulation of the beta-adrenergic response in cultured rat heart cells. I. Beta-adrenergic supersensitivity is induced by lactate via a phospholipase A2 and 15-lipoxygenase involving pathway. 164 55

We reported earlier that delta 9-tetrahydrocannabinol (THC), the main psychoactive ingredient in marihuana, increased markedly the level of unesterified arachidonic acid (AA) in guinea pig cerebral cortex slices prelabeled with [14C]AA. The purpose of the present study was to clarify the mechanism underlying THC-enhanced mobilization of AA. We could find little data to support an involvement for phospholipase A2 in this response. For example, the levels of lysophosphatidylcholine or lysophosphatidylethanolamine were not elevated after incubation with THC. A role for phosphoinositidase C-initiated lipolytic pathways was excluded, because neither basal nor acetylcholine-stimulated inositol phosphate formation was altered by THC. When we prelabeled slices with [14C]stearate or [3H]glycerol, THC did not elevate levels of unesterified [14C]stearate, nor did we observe significant changes in the phospholipids that were labeled with either precursor. These findings were in marked contrast to the previously reported reductions in [14C]AA-labeled phosphatidylinositol after exposure of prelabeled brain slices to THC; moreover, they suggested that the THC-induced effects on brain lipid metabolism in vitro were rather specific for AA. We show here that, when the acylation of brain lipids with AA was measured by addition of [3H]AA in the presence and absence of THC at zero time and incubation for 1 hr at 37 degrees, THC elicited marked, dose-dependent, and saturable reductions in esterified [3H]AA levels. The reductions in incorporation were balanced by increases in unesterified [3H]AA. The IC50 for the effect was on the order of 8 microM, and a maximal response occurred at 32 microM. We observed that the THC-induced suppression in acylation of the phospholipids by radiolabeled AA was up to 5-fold greater than the THC-elicited loss of AA from slices prelabeled before exposure to THC. The largest inhibitions of acylation were in phosphatidylinositol; the suppression of radioactivity in this phospholipid accounted for over 50% of the rise in unesterified [3H]AA. The radioactivity incorporated in triacylglycerols were also reduced markedly by THC. In contrast, the incorporation of radioactivity in phosphatidylcholine remained unaffected by THC. Taken together, these findings suggest that THC mobilizes AA by inhibiting acylation of certain lipids with AA, particularly phosphatidylinositol and triacylglycerol, rather than by liberating fatty acids by lipolysis. Comparison of the effects of several primary cannabinoids on lipid acylation with [3H]AA revealed that there was no relationship between the potencies of cannabinoids in inhibiting the incorporation of [3H]AA into membrane lipids and their psychoactive potencies in vivo; moreover, the stereoisomers of THC were equipotent.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1991 Oct
PMID:Delta 9-tetrahydrocannabinol inhibits arachidonic acid acylation of phospholipids and triacylglycerols in guinea pig cerebral cortex slices. 165 90

C-reactive protein (CRP) has been reported to deposit only to inflammatory sites, but not to normal sites. In present paper, we investigated involvements of fibronectin and lysophosphatidylcholine (lyso-PC) as responsible for this selectivity. In ELISA assay, CRP was found to bind to immobilized fibronectin with dose dependency, only in the presence of Ca2+ ions. Addition of 5 mM EDTA allowed CRP to abolish this binding. However, it could not be inhibited neither by phosphorylcholine nor by heparin. On the other hand, CRP could aggregate liposome consisted of lyso-PC and phosphatidylcholine (PC), but not that consisted of PC alone. Aggregation was found to be maximum when liposome with lyso-PC/PC molar ratio of 0.3 was used. Similar result was also observed in binding study with peroxidase-labelled CRP. In addition, phospholipase A2 treatment of liposome consisted of PC alone induced 3-fold higher binding than that found with untreated one. Ca2+ ions were required for binding to liposome.
Cell Mol Biol 1991
PMID:Involvements of fibronectin and lysophosphatidylcholine for selective binding of C-reactive protein. 165 91

The release of arachidonic acid by luteinizing hormone (LH) and the effects of inhibiting phospholipase A2 (PLA2) in vivo and in vitro on LH stimulated steroidogenesis in rat testis Leydig cells has been investigated. It was found that arachidonic acid is rapidly incorporated into phospholipids and is released within 1 min after addition of LH. The effects of treating adult rats with dexamethasone and human chorionic gonadotropin (hCG) in vivo on steroidogenesis and prostaglandin synthesis in Leydig cells isolated 6 h later were determined. It was found that hCG caused a marked increase in prostaglandin F2 alpha formation which was inhibited by treatment with dexamethasone. LH-stimulated testosterone production was inhibited in the hCG treated rats and dexamethasone caused a further decrease. Treatment with dexamethasone alone also caused a decrease in the response to LH. HCG, but not dexamethasone, had similar inhibitory effects on LH-stimulated cyclic AMP production. Similarly, the PLA2 inhibitors quinacrine, dexamethasone and corticosterone, added to the Leydig cells in vitro, inhibited LH-stimulated testosterone production but not cyclic AMP production. 11-Dehydrocorticosterone also inhibited LH-stimulated testosterone production, but higher concentrations were required to give 50% inhibition compared to corticosterone (50 and 25 microM, respectively). Ring A-reduced metabolites of corticosterone and progesterone were also found to inhibit LH-stimulated steroidogenesis. The results obtained in this and previous studies are consistent with the activation of PLA2, (either directly by LH and/or via cyclic AMP), which results in the release of arachidonic acid and the formation of leukotrienes, which stimulate steroidogenesis in the Leydig cell. This study also indicates that corticosteroids and their metabolites may exert inhibitory effects at other sites in the steroidogenic pathways, in addition to PLA2.
J Steroid Biochem Mol Biol 1991
PMID:Release of arachidonic acid and the effects of corticosteroids on steroidogenesis in rat testis Leydig cells. 165 82

A myotoxic phospholipase A2, named bothropstoxin II (BthTX-II), was isolated from the venom of the South American snake Bothrops jararacussu and the pathogenesis of myonecrosis induced by this toxin was studied in mice. BthTX-II induced a rapid increase in plasma creatine kinase levels. Histological and ultrastructural observations demonstrate that this toxin affects muscle fibers by first disrupting the integrity of plasma membrane, as "delta lesions" were the earliest morphological alteration and since the plasma membrane was interrupted or absent in many portions. In agreement with this hypothesis, BthTX-II released peroxidase entrapped in negatively charged multilamellar liposomes and behaved as an amphiphilic protein in charge shift electrophoresis, an indication that its mechanism of action might be based on the interaction and disorganization of plasma membrane phospholipids. Membrane damage was followed by a complex series of morphological alterations in intracellular structures, most of which are probably related to an increase in cytosolic calcium levels. Myofilaments became hypercontracted into dense clumps which alternated with cellular spaces devoid of myofibrillar material. Later on, myofilaments changed to a hyaline appearance with a more uniform distribution. Mitochondria were drastically affected, showing high amplitude swelling, vesiculation of cristae, formation of flocculent densities, and membrane disruption. By 24 hr, abundant polymorphonuclear leucocytes and macrophages were observed in the interstitial space as well as inside necrotic fibers. Muscle regeneration proceeded normally, as abundant myotubes and regenerating myofibers were observed 7 days after BthTX-II injection. By 28 days regenerating fibers had a diameter similar to that of adult muscle fibers, although they presented two distinctive features: central location of nuclei and some fiber splitting. This good regenerative response may be explained by the observation that BthTX-II does not affect blood vessels, nerves, or basal laminae.
Exp Mol Pathol 1991 Dec
PMID:Skeletal muscle degeneration and regeneration after injection of bothropstoxin-II, a phospholipase A2 isolated from the venom of the snake Bothrops jararacussu. 166 Aug 22

Lutropin (LH) receptors in rat granulosa cells are expressed by activation of cAMP-dependent protein kinase in response to follitropin (FSH). In the present study, 12-O-tetradecanoylphorbol 13-acetate (TPA) could cause a dose-dependent expression of LH receptors in the presence of insulin, but not in the absence of insulin, as measured by binding of 125I-deglycosylated human choriogonadotropin (DGhCG). The synergistic action of TPA with insulin was achieved at 1 nM and 10 mIU/ml, respectively. The receptor expression induced by this synergistic action was accompanied by cAMP accumulation which was detected after a lag time of 6 h following exposure to TPA. However, a synthetic diacylglycerol and non-protein kinase C activating phorbol derivatives did not mimic the effect of TPA on the receptor expression. In addition, insulin modulated the inhibitory effect of TPA in FSH-induced LH receptor expression, indicating a peculiar action of insulin in the receptor expression. Indomethacin treatment led to a dose-dependent inhibition in the receptor expression in the cells treated with TPA plus insulin more than that in the cells with FSH plus insulin, suggesting that the synergistic action was dependent upon cyclooxygenase and/or phospholipase A2 activity. It was shown by Scatchard analysis of LH receptors and kinetic studies of hCG-stimulated cAMP formation that the synergistic action of TPA with insulin led to expression of functional LH receptors coupled with the adenylate cyclase system in cultured granulosa cells.
Mol Cell Endocrinol 1991 Oct
PMID:Tumor-promoting phorbol ester acts synergistically with insulin to induce lutropin receptor expression in rat granulosa cells. 166 32


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