Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Long wave ultraviolet radiation (UVA) has been shown to play an important role in the overall response of skin to solar radiation, including sunburn, tanning, premature aging, and non-melanoma skin cancer. UVA induction of inflammation in human skin is thought to be mediated by membrane lipid derived products. In order to investigate the mechanism of this response we examined the effect of UVA on phospholipid metabolism of human epidermal keratinocytes in culture. Keratinocytes were grown in serum free low calcium medium. The cells were prelabeled with [3H] arachidonic acid or [3H] choline and irradiated with UVA (Honle 2002-Hg vapor lamp). Identification and quantitation of specific membrane phospholipid-derived components was achieved using high-performance liquid chromatography, paper chromatography, and radioimmunoassay. UVA resulted in a linear dose dependent release of [3H] arachidonic acid into medium between 1 and 20 joule/cm2. This response was inhibited in an oxygen-reduced environment. The radiolabel released was predominantly free arachidonate and cyclooxygenase metabolites. Cyclooxygenase metabolites prostaglandin E2 and prostacyclin derivative, 6-keto-prostaglandin F1a, were stimulated following UVA irradiation, but the lipoxygenase metabolite, leukotriene B was not detected. Maximal release was measured immediately after irradiation and changed little over 24 h post-irradiation. UVA stimulated an increase of [3H] choline metabolites glycerophosphorylcholine and phosphorylcholine in media extracts suggesting UVA activation of phospholipase C and phospholipase A2 or diacylglyceride lipase.
J Invest Dermatol 1990 Aug
PMID:Long-wave ultraviolet light induces phospholipase activation in cultured human epidermal keratinocytes. 211 82

Evidence suggests that the phospholipase C/protein kinase C signal transduction system participates in the regulation of epidermal cell growth and differentiation. Psoriatic epidermis is characterized by hyperproliferation, defective differentiation, and inflammation. In this report, we have determined the activity of phospholipase C-catalyzed hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) and 1,2-diacylglycerol content in normal and psoriatic involved and uninvolved epidermis. 1,2-diacylglycerol is formed from phospholipase C-catalyzed hydrolysis of PIP2 and is the physiologic activator of protein kinase C. PIP2 hydrolysis was assayed in soluble and particulate fractions prepared from keratome biopsies of normal and psoriatic skin. Total lipids were extracted from normal and psoriatic epidermis and 1,2-diradylglycerol (a mixture of 1,2-diacylglycerol and 1-ether, 2-acyl-glycerol) quantitated by enzyme assay. Because 1,2-diacylglycerol is a more potent activator of protein kinase C, the relative proportions of 1,2-diacyl and 1-ether, 2-acylglycerol in uninvolved and involved psoriatic epidermis were determined. This was accomplished by separation of acetate derivatives of 1,2-diacylglycerol and 1-ether, 2-acyl-glycerol by thin layer chromatography. Soluble and membrane-associated phospholipase C-catalyzed PIP2 hydrolysis were increased 3.7 times (p less than 0.001) and 3 times (p less than 0.004), respectively, in psoriatic involved compared to uninvolved and normal epidermis. 1,2-diradylglycerol content was also significantly elevated (3 times, p less than 0.01) in psoriatic involved versus uninvolved and normal epidermis. Analysis of the acetate derivatives of 1,2-diradylglycerol in psoriatic uninvolved and involved epidermis revealed that 1,2-diacylglycerol was the major species (86% and 95%, respectively). There were no significant differences in either phospholipase C-catalyzed PIP2 hydrolysis or 1,2-diacylglycerol content between uninvolved and normal epidermis. 1,2-diacylglycerol purified from normal and involved psoriatic epidermis was capable of activating protein kinase C from normal epidermis in vitro. In epidermal slices, activation of protein kinase C by addition of 12-0-tetradecanoylphorbol-13-acetate and 1,2-diacylglycerol (1,2-dioctanoylglycerol) resulted in subsequently decreased protein kinase C activity, a process termed down-regulation. These data are consistent with the possibility that the elevation in lesional 1,2-diacylglycerol content may account, in part, for the previously reported reduction of protein kinase C activity in psoriasis (Horn, Marks, Fisher, et al: J Invest Dermatol 88:220-222, 1987).
J Invest Dermatol 1990 Oct
PMID:Increased phospholipase C-catalyzed hydrolysis of phosphatidylinositol-4,5-bisphosphate and 1,2-sn-diacylglycerol content in psoriatic involved compared to uninvolved and normal epidermis. 217 May 39

The effects of bradykinin on activation of phosphoinositide turnover, 1,2-diglyceride formation, and growth of cultured adult human keratinocytes were investigated. Keratinocytes specifically bound [3H]bradykinin with high affinity (kd = 3.4 nM) and displayed 1.5 X 10(5) binding sites/cell. Bradykinin caused a rapid dose-dependent increase in inositol trisphosphate (IP3) inositol bisphosphate, and inositol monophosphate. IP3 was maximally increased (fivefold) at 30 s and remained elevated for at least 10 min. Half maximal stimulation of IP3 formation was observed at 27 nM bradykinin. IP3 accumulation was equally elevated by bradykinin and lys-bradykinin but was not stimulated by des-Arg9-bradykinin, indicating that phospholipase C in cultured keratinocytes is coupled to B2 bradykinin receptors. Treatment of keratinocytes with active phorbol ester (TPA) caused a significant inhibition (50%) of bradykinin-induced IP3 accumulation, suggesting negative regulation of phospholipase C by protein kinase C. Bradykinin also caused a significant elevation in 1,2-diacylglycerol (DAG) content. DAG content was maximally elevated (twofold) at 1 min and remained elevated for at least 10 min. Bradykinin also caused a significant (twofold, p less than 0.02) increase in keratinocyte growth. These data demonstrate that bradykinin is a potent agonist of the phospholipase C/protein kinase C signal transduction system in cultured adult human keratinocytes and that activation of this pathway by bradykinin is associated with increased keratinocyte growth.
J Invest Dermatol 1990 Dec
PMID:Bradykinin induces phosphoinositide turnover, 1,2-diglyceride formation, and growth in cultured adult human keratinocytes. 217 49

The ability of a variety of agonists to induce formation of inositol phosphates and 1,2-diacylglycerol in cultured adult human keratinocytes has been investigated. Histamine, bradykinin, and thrombin significantly stimulated formation of inositol mono-, bis-, and trisphosphate and 1,2-diacylglycerol within 5 min after addition. Aluminum fluoride also caused a dose-dependent accumulation of inositol phosphates suggesting the participation of a GTP binding protein in the regulation of phospholipase C-catalyzed phosphoinositide hydrolysis. These data demonstrate that human keratinocytes possess the capacity for phospholipase C-mediated signal transduction and suggest that this pathway may participate in the regulation of keratinocyte function.
J Invest Dermatol 1989 Aug
PMID:Agonist-induced hydrolysis of phosphoinositides and formation of 1,2-diacylglycerol in adult human keratinocytes. 247 31

Phosphatidylinositol (PI) kinase is activated by growth factors, such as epidermal growth factor (EGF), and is thought to be involved in cellular proliferation. Psoriasis is a hyperproliferative epidermal disease in which EGF receptor expression is altered and phospholipase C activity is increased. Considering the potential importance of growth factor stimulated phosphoinositide metabolism in the genesis of abnormal growth, we measured PI kinase activity in epidermal keratome biopsies from normal skin and the lesional and nonlesional skin of psoriatic patients. The PI kinase activity in 10 psoriatic involved plaques was increased 6.7-fold (Vmax = 67.1 +/- 23.9 pmol formed/min/mg protein +/- SE) when compared with 11 normal epidermal biopsies (Vmax = 10.0 +/- 1.3 pmol/min/mg protein, p less than 0.025). Similar results were noted when enzyme activity was standardized using DNA content. The apparent Km of PI kinase for ATP in involved psoriatic biopsies (0.45 +/- 0.14 mM) was also significantly (p less than 0.025) increased compared with normals (0.11 +/- 0.02 mM). The PI kinase activity in 11 biopsies of nonlesional psoriatic epidermis was not statistically different from normal epidermis. Both psoriatic and normal PI kinases required Mg++ and were inhibited by Ca++. The polyamine, spermine, a known activator of PI kinase in other tissues, stimulated normal but not psoriatic epidermal PI kinase. Both normal and psoriatic PI kinase activities had an apparent mol wt of 85,000. Increased synthesis of phosphoinositides by PI kinase in psoriatic tissue may provide more substrate for phospholipase C; a key enzyme in growth factor-mediated signal transduction.
J Invest Dermatol 1989 Jun
PMID:Increased phosphatidylinositol kinase activity in psoriatic epidermis. 254 14

The regulation of soluble phosphoinositide-specific phospholipase C from adult human epidermis by guanine nucleotide was investigated. In the presence of physiologic concentrations of Ca++ (1 microM) and Mg++ (1.5 mM), neither phosphatidylinositol (PI) nor phosphatidylinositol-4,5-bisphosphate (PIP2) were appreciably hydrolyzed. Addition of guanosine-5'-triphosphate (GTP) or guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S) significantly stimulated hydrolysis of PIP2, but not PI. Stimulation of PIP2 hydrolysis by GTP was dose-dependent between 1-100 microM GTP. Other nucleoside triphosphates and nucleotide analogues were unable to substitute for GTP or GTP-gamma-S. A GTP-gamma-S-stimulated PIP2 hydrolysis was inhibited by guanosine-5'-O-(2-thiodiphosphate (GDP-beta-S). The phospholipase C preparation specifically bound [35S]GTP-gamma-S and this binding was also inhibited by GDP-beta-S. In addition to a 41,000-dalton pertussis toxin substrate, the phospholipase C preparation contained 3-4 GTP binding proteins with molecular weights between 20,000-30,000. These data demonstrate that human epidermis contains a soluble GTP-dependent phospholipase C activity that specifically hydrolyzes PIP2 and suggest that this reaction is regulated by a GTP-binding protein(s).
J Invest Dermatol 1989 Jun
PMID:GTP-dependent hydrolysis of phosphatidylinositol-4,5-bisphosphate by soluble phospholipase C from adult human epidermis. 254 16

We have studied the induction of procoagulant activity (PCA) by lipopolysaccharide (LPS) in cultured human epidermal cells. Single cell suspensions of epidermal cells were prepared from surgical specimens and stimulated for 24 h with LPS (100 micrograms/ml). PCA was determined by one-stage clotting assay. Stimulation of the epidermal cells with LPS resulted in a significant reduction of the clotting time (approx. 30%) as compared with the nonstimulated controls. Further analysis of the induced PCA showed that it did not require factors of the intrinsic pathway of the clotting cascade (factors XI and XII). Similarly, PCA was not affected by factor IX-deficient plasma but required factors II, VII, and X for its full expression. PCA was inactivated by treatment with phospholipase C but not by heating to 56 degrees C. These data indicate that the epidermal cell PCA resembles tissue factor-like activity, activating the extrinsic clotting pathway. Elimination of Langerhans' cells from the epidermal cell suspension by antibody and complement-mediated lysis did not result in a reduction of PCA in the remaining epidermal cells, indicating that keratinocytes were most likely the producer cells. Induction of PCA on the cell membrane surface of epidermal cells may be an early event resulting in the initiation of a local inflammatory reaction.
Arch Dermatol Res 1989
PMID:Induction of procoagulant activity in human epidermal cells. 280 62

Arachidonic acid (AA), the precursor of prostaglandins and leukotrienes, can be directly liberated from membrane phospholipids by phospholipase A2 or indirectly by phospholipase C. One or both of these enzymes may be responsible for the increased content of AA found in psoriatic lesional epidermis. Keratome biopsies were obtained from normal and psoriatic individuals. After homogenization and sonication, a 10,000 g supernatant was used as the enzyme source. The activities of both phospholipase A2 and C were assayed in each sample using phosphatidylcholine and phosphatidylinositol, respectively, as substrates. Phospholipase A2 activity was found to be significantly higher than normal in both uninvolved and lesional psoriatic epidermis. In contrast, phospholipase C activity was significantly higher than normal in only the psoriatic plaque on the basis of wet weight (p less than 0.001), protein (p = 0.01), and DNA (p = 0.004) content. Phospholipase C activity in pmol diacylglycerol formed/min/microgram DNA was: normal 4.96 +/- 0.80, n = 13; uninvolved 7.29 +/- 1.06, n = 18; plaque 14.44 +/- 2.50, n = 18. Analysis (pH profile, calcium requirement, substrate specificity, and saturation kinetics) of pooled epidermal extracts showed no inherent differences in phospholipase C from normal and psoriatic epidermis, suggesting either a higher concentration or the presence of an activated form of the enzyme in psoriatic plaque. Since phospholipase C activity, in contrast to phospholipase A2 activity, is elevated only in lesional epidermis, it is possible that this enzyme contributes to AA accumulation observed in this tissue.
J Invest Dermatol 1987 Apr
PMID:Partial characterization of phospholipase C activity in normal, psoriatic uninvolved, and lesional epidermis. 355 72

The possibility that phospholipid deacylation may be a critical event in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-associated effects on mouse skin prompted us to examine in vitro the effects of TPA on arachidonic acid metabolism in neonatal mouse keratinocytes. Three-day old neonatal keratinocytes were prelabeled with [14C]arachidonic acid ([14C]AA) and [14C] stearic acid ([14C]ST) and used to characterize the lipases that were activated when these cells were treated with TPA in culture. Data from these studies demonstrate that phosphatidylcholine (PC) and phosphatidylinositol (PI) are the major phospholipids that undergo early hydrolysis to release arachidonic acid when challenged by TPA. Of particular interest was the novel observation of the hydrolysis of 14C-labeled PI in these keratinocytes, the accumulation of [14C]1,2-diacylglyceride and the lack of the [14C]diacylglyceride phosphorylation to form [14C]phosphatidic acid. This lack of [14C] phosphatidic accumulation implied that although TPA enhanced the hydrolysis of [14C]PI resulting in increased [14C]diacylglyceride it did not enhance the resynthesis of the [14C]PI via the phosphorylation of the [14C]diacylglyceride. Therefore, TPA probably is not involved in the turnover of PI in these cells but is involved in the activation of PC hydrolyzing phospholipase A2 and PI hydrolyzing phospholipase C in these keratinocytes releasing arachidonic acid which then undergoes oxygenation reactions to provide biologically active eicosanoids.
J Invest Dermatol 1985 Oct
PMID:Modulation of phospholipid metabolism in murine keratinocytes by tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. 393 Jun 15

The precise mechanism for acantholysis after pemphigus IgG binds to the cell surface is as yet unknown, although involvement of proteinases such as plasminogen activator (PA) has been suggested. We previously reported that pemphigus IgG, but not normal nor bullous pemphigoid IgGs, caused a transient increase in intracellular calcium ([Ca++]i) and inositol 1,4,5-trisphosphate (IP3) concentration in cultured DJM-1 cells (a squamous cell carcinoma line). To clarify whether phospholipase C is involved in this process after the antibody binds to the cell surface, we examined the effects of a specific phospholipase C inhibitor (U73122) on the pemphigus IgG-induced increase in [Ca++]i, IP3, PA secretion, and cell-cell detachment in DJM-1 cells. [Ca+2]i and IP3 contents were determined with or without 30-min pre-incubation with U73122 or an inactive analogue (U73343) with fura-2 acetoxymethylester and a specific IP3 binding protein, respectively. PA activity in the culture medium was measured after various incubation periods with pemphigus IgG by two-step amidolytic assay. The detachment of cell-cell contacts was examined by detecting the retraction of keratin filament bundle from cell-cell contact points to the perinuclear region by immunofluorescence microscopy using anti-keratin antibody. Pemphigus IgG immediately increased [Ca++]i and IP3 content. PA activity in the culture medium has also been increased at 24 h after pemphigus IgG was added in association with cell-cell detachment. However, pre-incubation with U73122 (1-10 microM), but not with U73343 (10 microM), dramatically reduced the pemphigus IgG-induced increases in [Ca++]i, IP3, and PA activity and inhibited the pemphigus IgG-induced cell-cell detachment. Both U73122 and U73343 caused no effects on cell viability and IgG binding to the cell surface. These results suggest that phospholipase C plays an important role in transmembrane signaling leading to cell-cell detachment exerted by pemphigus IgG binding to the cell surface.
J Invest Dermatol 1995 Sep
PMID:Pharmacologic evidence for involvement of phospholipase C in pemphigus IgG-induced inositol 1,4,5-trisphosphate generation, intracellular calcium increase, and plasminogen activator secretion in DJM-1 cells, a squamous cell carcinoma line. 766 7


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