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

We investigated the expression of Ly-6.A2 on isolated murine epidermal cells by flow cytometry. Ly-6.A2 was expressed on 61% of keratinocytes and 6% of dendritic epidermal T cells of C57BL mice. Phosphatidylinositol-specific phospholipase C removed Ly-6.A2, indicating that the antigen is anchored to the keratinocyte membrane via a glycosyl-phosphatidylinositol anchor similar to its attachment to the membrane of lymphocytes. Induction of dermatitis by topical application of PMA increased the expression of Ly-6.A2 on TCR gamma delta+ dendritic epidermal T cells and did not change its expression on keratinocytes. The increased expression of Ly-6.A2 on dendritic epidermal T cells was transient and reached a peak at 4 days after application of PMA, when 55% of the cells were positive.
J Dermatol Sci 1993 Apr
PMID:Constitutive expression of Ly-6.A2 on murine keratinocytes and inducible expression on TCR gamma delta+ dendritic epidermal T cells. 810 78

In murine keratinocytes, Ca(++)-induced terminal differentiation is accompanied by a rapid and sustained increase of inositol phosphates and diacylglycerol. Based on Western blotting analysis, basal keratinocytes cultured in 0.05 mM Ca++ medium express phospholipase C (PLC)-gamma 1 predominantly and no detectable PLC-beta 1. Differentiating keratinocytes cultured in 1.4 mM Ca++ express two- to threefold more PLC-gamma 1 protein and PLC-delta 1, but no detectable PLC-beta 1. Although the amount of PLC-gamma 1 and -delta 1 protein increased, PLC-gamma 1 and -delta 1 mRNA decreased in differentiating cells. Thus the sustained rise of PLC activity induced by Ca++ in differentiating keratinocytes may be associated with higher amounts of both PLC-gamma 1 and -delta 1 in maturing cells, determined by a posttranscriptional mechanism. Tyrosine phosphate content in PLC-gamma 1 was low in basal cells and did not change in cells exposed to 1.4 mM Ca++. However, genistein inhibited the increase in PLC activity induced by 1.4 mM Ca++. In contrast, transforming growth factor (TGF)alpha, which stimulates both PLC activity and growth in basal keratinocytes, increased tyrosine phosphorylation of PLC-gamma 1. These results suggest that tyrosine phosphorylation of PLC-gamma 1 by the epidermal growth factor (EGF) receptor is linked to stimulated proliferation, whereas stimulation of PLC activity by Ca++ is linked to keratinocyte differentiation and involves the action of a tyrosine kinase but not tyrosine phosphorylation of PLC-gamma 1. Based on studies using the intracellular free Ca++ chelator BAPTA, a rise in intracellular free Ca++ was not required for stimulation of PLC activity by raising extracellular Ca++. Phorbol esters inhibited PLC stimulation by 1.4 mM Ca++ medium and increased serine phosphorylation of PLC-gamma 1. Exogenous phosphatidylinositol-specific and phosphatidylcholine-specific bacterial PLC also inhibited endogenous inositol phosphate formation and increased endogenous diacylglycerol (DAG). Thus, direct serine phosphorylation of PLC-gamma 1 by protein kinase C is associated with the inhibition of Ca(++)-mediated PLC stimulation. These results show that keratinocytes have multiple mechanisms to regulate PLC activity in response to a specific signal.
J Invest Dermatol 1993 Nov
PMID:Keratinocyte differentiation is associated with changes in the expression and regulation of phospholipase C isoenzymes. 822 34

We produced a highly reproducible experimental impetigo-like lesion in normal human skin explants in culture. The three Staphylococcus aureus strains we used were an isolate from a human impetigo (E strain), an isolate from a human furunculosis (N strain) and ATCC 29213 strain. E strain was a protein A positive, coagulase type V, producer of exfoliative toxin (ET) and beta-toxin. N strain was a coagulase type IV, ET non-producer and alpha-toxin positive. ATCC 29213 was a coagulase type II, ET non-producer, and alpha-, beta-, and delta-toxin positive. Normal human skin samples were obtained from 8 adult skin surgery patients. One specimen was obtained from human oral mucosa. Small pieces of the samples were slightly abraded on the epidermal surface and cultured on lens paper rafts floating in Eagle's Minimum Essential Medium in an atmosphere of 5% CO2 and 95% air. Fifty microliters of the respective bacterial suspensions were applied to the epidermal surfaces of the explants. The inoculated surfaces were then occluded under sterile plastic plaster. Histologically, the formation of intraepidermal blisters at the granular layer level with acantholytic cells was observed in all 8 of the skin specimens at 10 h after inoculation with E strain. The specimen from an oral mucous membrane did not produce similar changes with any of the three S. aureus strains. Neither N or ATCC strains developed bullae in the epidermis at 6, 10 or 18 h after inoculation. Immunofluorescent examination revealed that the inner surfaces of blisters in the epidermis were lined with anti-ETA antibody. Under the electron microscope, the blisters of the specimens which had been inoculated with strain E contained only a few S. aureus cells. These results suggest that blister formation at the granular layer level with acantholytic cells is mediated by ET action at the granular layer level and occurs without invasion of lymphocytes or neutrophils, or the involvement of any serum components. Therefore, under appropriate conditions, impetigo could develop even in adults.
J Dermatol Sci 1993 Jun
PMID:Production of staphylococcal impetigo-like lesion on human skin explants in culture. 824 Oct 71

Phospholipase C-mediated release of inositol trisphosphate, followed by an increase in free intracellular calcium, is an important signal transduction pathway for several membrane receptors. In the present investigation, the coupling of various receptors to phospholipase C was studied in the human keratinocyte line HaCaT. Inositol trisphosphate formation was determined by anion-exchange chromatography, and the release of intracellular calcium was analysed with the fluorescence probe Fura-2 AM. Activation of HaCaT keratinocytes with bradykinin resulted in a time- and dose-dependent release of inositol trisphosphate and intracellular calcium, with an EC50 value of 50 nM for bradykinin-induced inositol trisphosphate formation. The mediators and cytokines IL-1, IL-4, IL-6, IL-8, EGF and TGF alpha, as well as bombesin, prolactin, carbachol, substance P and retinoic acid, did not activate this pathway. The inability of the mediators examined to activate phospholipase C may be due to lack of the respective cognate receptors or to the use of other signal transduction pathways.
Arch Dermatol Res 1993
PMID:Inositol phosphate formation and release of intracellular free calcium by bradykinin in HaCaT keratinocytes. 830 79

Heat-stable antigen (HSA), expressed by various antigen-presenting cells (APC), has been described as a costimulatory molecule for CD4+ T cells. Recently, we observed that HSA also serves as an important costimulatory molecule on epidermal Langerhans cells (LC). During these studies, low levels of HSA staining were also detected on normal murine keratinocytes (KC). To investigate whether HSA also is involved in T-cell activation by KC, normal murine KC or the spontaneously transformed KC cell-line PAM 212 were treated with PDB or PMA to induce HSA-expression. FACS analyses showed induction of HSA expression on normal murine KC, as well as PAM 212 cells. In functional assays PDB or PMA-treated normal or transformed KC were far more potent inducers of primary allogeneic T-cell responses than untreated KC. Addition of anti-HSA-specific mAb 20C9 specifically inhibited the costimulatory activity of KC, an effect that was even more pronounced when CTLA-4Ig was added to the cultures. Cleavage of HSA on KC surfaces by a phosphoinositol-specific phospholipase C (PI-PLC) also significantly inhibited the costimulatory capacity of KC for naive CD4+ T cells. In aggregate, our data indicate that expression of HSA on activated KC contributes to the capacity of these cells to induce proliferation of allogeneic T cells.
Exp Dermatol 1995 Oct
PMID:Heat-stable antigen is expressed by murine keratinocytes and delivers costimulatory signals in T-cell activation. 858 19

Following the activation of specific receptors, phospholipase C has been shown to cleave the membrane phospholipid phosphatidylinositol bisphosphate into the 2nd messengers inositol 1,4,5-trisphosphate and diacylglycerol. Both 2nd messengers contribute to the regulation of cellular proliferation. The receptor for bradykinin is coupled to this pathway in keratinocytes, but knowledge about other activators of phospholipase C is limited. Additional mediators and agents were therefore examined regarding their ability to activate phospholipase C in HaCaT keratinocytes. Analysis for 3H-inositol phosphates was performed by anion-exchange HPLC. Thrombin and melittin induced a time- and dose-dependent release of inositol 1,4,5-trisphosphate. Several other mediators examined such as angiotension II, neurotensin, C3a, pituitary adenylate cyclase activating peptide, phenylephrin, and prostaglandin E2, did not induce the formation of inositol phosphates. In view of the mitogenic activity and the increased formation of thrombin after tissue injury, the coupling of the thrombin receptor to phospholipase C in HaCaT keratinocytes suggests a role of this protease in epidermal wound healing.
Exp Dermatol 1996 Apr
PMID:Thrombin and melittin activate phospholipase C in human HaCaT keratinocytes. 873 16

It has been proposed that toxins and other bacterial protein products of Staphylococcus aureus can act as triggers or persistence factors in several inflammatory skin diseases. In this study, we examined the S. aureus isolates from the skin of patients with atopic dermatitis and psoriasis. We found that the bacterial isolates from these patients exhibited either characteristic superantigenic toxins or thermolabile toxins believed to be staphylococcal alpha-toxin. All of these staphylococcal strains also secreted extracellular staphylococcal protein A. We found significant differences in the action of these toxins on human keratinocytes and keratinocyte cell lines. The superantigenic toxins toxic shock syndrome toxin-1, staphylococcal enterotoxins A and B, and exfoliative toxin-A, as well as staphylococcal protein A, did not induce significant cytotoxic damage in the keratinocyte cell line HaCaT, whereas the staphylococcal alpha-toxin produced profound cytotoxicity. Keratinocyte cytotoxicity induced by staphylococcal alpha-toxin was time and concentration dependent and demonstrated the morphologic and functional characteristics of necrosis, not apoptosis. Addition of alpha-toxin to keratinocytes simultaneously induced cell lysis and tumor necrosis factor-alpha release into the medium within 30 min; apparently, it was constitutive tumor necrosis factor-alpha. On the other hand, superantigenic toxins and, in particular, protein A showed stimulation of tumor necrosis factor-alpha secretion in keratinocytes and release of this cytokine after 6-12 h of incubation. Thus, staphylococcal protein A, alpha-toxin, and superantigenic toxins found in S. aureus isolates from patients with psoriasis and atopic dermatitis can produce direct pro-inflammatory effects on keratinocytes through the release of tumor necrosis factor-alpha. We propose that these effects may be relevant to the induction and persistence of lesions in these two diseases.
J Invest Dermatol 1996 Oct
PMID:Staphylococcal toxins and protein A differentially induce cytotoxicity and release of tumor necrosis factor-alpha from human keratinocytes. 882 68

We have demonstrated previously that pemphigus vulgaris (PV)-IgG induces activation of phospholipase C (PLC), production of inositol 1,4,5-trisphosphate, and a rapid transient increase in [Ca2+]i in cultured human keratinocytes, leading to secretion of plasminogen activator and cell-cell detachment in cell culture. In the current study, to examine the involvement of protein kinase C (PKC) in the mechanism of blister formation in PV, we studied the PV-IgG-induced translocation of PKC isozymes from the cytosol to the particulate/cytoskeleton (p/c) fractions and the activation of PKC in human keratinocytes. Cells cultured in Eagle's minimum essential medium were incubated with PV-IgGs for 30 s, 1 min, 5 min, or 30 min. PV-IgG binding to the cell surface antigen (desmoglein III) induced translocation of PKC-alpha from the cytosol to the p/c fractions within 30 s, with a peak at 1 min that lasted at least 30 min. PKC-delta also was translocated within 1 min and reached a peak at 5 min but was reduced to basal levels at 30 min. Alternatively, PKC-eta translocation to the p/c fraction was induced slowly, taking more than 5 min, and was reduced to approximately half-maximum at 30 min, whereas PKC-zeta translocation reached a maximum at 30 s, rapidly returning to baseline by 5 min after PV-IgG stimulation. The total PKC activity in the p/c fraction also was increased after PV-IgG exposure, peaked at 1 min, and was sustained for at least 30 min. These findings suggest that a unique activation profile of PKC isomers may be involved in mediating the intracellular signaling events induced by PV-IgG binding to desmoglein III in cultured human keratinocytes.
J Invest Dermatol 1997 Apr
PMID:Pemphigus IgG activates and translocates protein kinase C from the cytosol to the particulate/cytoskeleton fractions in human keratinocytes. 907 78

Skin colonization with Staphylococcus aureus may exacerbate skin disorders by activation of lesional T cells with release of superantigens. Although T cells are effectively stimulated by staphylococcal superantigens in the presence of epidermal accessory cells, it remains to be elucidated whether in vivo cutaneous colonization with S. aureus can activate T cells. We examined how T cells are stimulated in the presence of keratinocytes by mitomycin C (MMC)-treated S. aureus that are unable to propagate but retain their ability to produce superantigens. Peripheral blood mononuclear cells (PBMCs) proliferated well in response to MMC-treated superantigen-producing S. aureus and bacterial supernatants. When purified T cells were cultured with MMC-treated S. aureus or supernatant in the presence of interferon-gamma-pre-treated keratinocytes, the supernatant, but not MMC-treated S. aureus, stimulated T cells. MMC-treated S. aureus had a cytotoxic effect on keratinocytes. Furthermore, keratinocytes were highly susceptible to alpha-toxin compared with monocytes and B cells functioning as accessory cells in PBMCs. This suggests that a lack of response of T cells to S. aureus plus keratinocytes is due to damage of superantigen-presenting function of keratinocytes by cytolysin. The activity of alpha-toxin was much less stable than that of superantigen during incubation. Given that S. aureus-colonized skin provides circumstances in which viable keratinocytes are exposed to superantigens but not to active cytolysin(s), skin-infiltrating T cells may be effectively stimulated by S. aureus.
J Invest Dermatol 1997 Apr
PMID:T-cell proliferation to superantigen-releasing Staphylococcus aureus by MHC class II-bearing keratinocytes under protection from bacterial cytolysin. 907 79

To elucidate the signaling mechanisms associated with keratinocyte differentiation, we studied in vitro phospholipase C-mediated signal transduction, which results in the generation of inositol phosphates, comparing proliferating versus differentiated HaCaT cells, a human keratinocyte line. Bradykinin- or A23187-induced formation of inositol 1,4,5-trisphosphate, inositol 1,4-bisphosphate, and inositol monophosphates, as determined by anion exchange high performance liquid chromatography, were found to be highest in the early logarithmic growth phase of the cells. In more highly differentiated HaCaT cells, which expressed maximal amounts of the differentiation marker involucrin, inositol phosphate formation was reduced to about one third of that in proliferating cells. Thin layer chromatography of membrane phosphatidylinositol phosphates revealed that this reduction was associated with a steady decrease in phospholipase C substrates. Immunoblot analysis of phospholipase C isozymes, however, and of expression of Gq alpha, the G protein subunit that activates phospholipase C beta, revealed no decrease during the differentiation phase. The results suggest that the inositol-phospholipid signal transduction pathway is involved in keratinocyte proliferation and in the induction of differentiation, with attenuated signal transduction activity via phospholipase C-coupled receptors in more differentiated keratinocytes.
J Invest Dermatol 1997 May
PMID:Phospholipase C-mediated signaling is altered during HaCaT cell proliferation and differentiation. 912 27


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