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)

The enzyme sphingomyelinase (sphingomyelin phosphorylcholine phosphohydrolase E.C.3.1.4.12) which hydrolyzes sphingomyelin to ceramide (N-acylsphingosine) and phosphorylcholine was identified in the subcellular fractions of pig and human epidermis. The enzyme has an optimum pH of 4.5 to 5 and is activated by Triton X-100 (0.1% w/v). Approximately two-thirds of the enzyme activity in both the pig and human epidermal homogenates was in the soluble subcellular fraction and more than half of the enzyme activity in the subcellular particulate fraction was solubilized by freeze-thawing. The pH optimum suggests that epidermal sphingomyelinase is probably a lysozomal enzyme. The enzymes in both pig and human epidermis exhibited Michaelis-Menten kinetics. The soluble sphingomyelinase in pig epidermis had an apparent Km, 4.5 X 10(-5) M and that in human epidermis an apparent Km 7.7 X 10(-5) M. The pig epidermal sphingomyelinase had no special requirement for either divalent or heavy metal ions and was not inhibited by sulfydryl group-blocking agents but it was moderately inhibited by dithiothreitol. No evidence was found in either pig or human epidermis for the presence of a phospholipase C (E.C.3.1.4.3) which hydrolyzes phosphatidylcholine to diglyceride and phosphorylcholine but there was suggestive evidence of another catabolic pathway for phosphatidylcholine.
J Invest Dermatol 1978 Jun
PMID:Sphingomyelinase in pig and human epidermis. 2 35

Guinea-pig epidermal cells in culture possess a glycocalyx coat similar to that in vivo, as revealed by the ruthenium red stating technique. Trypsin, phospholipase C, and lysozyme do not produce any changes of the glycocalyx, while hyaluronidase and neuraminidase lead to partial and subcomplete removal respectively. Cells stripped of their glycocalyx coat by neuraminidase do not detach from the support and do not show any signs of toxicity. There is complete reconstitution of the glycocalyx within 24 hr.
J Invest Dermatol 1975 Jan
PMID:Glycocalyx of epidermal cells in vitro: demonstration and enzymatic removal. 4 27

Three methods of measuring the epidermolytic toxin Staphylococcus aureus-bioassay in newborn mice, radial immunodiffusion, and radioimmunoassay-were compared for reproducibility, specificity, and sensitivity. The bioassay is highly specific and remains the only functional assay. It is reproducible only if newborn mice of the same age are used. The time required for epidermolysis follows a dose-response relationship only if concentrations of toxin large enough to cause peeling in 90 min or less are used. This limits the sensitivity of the bioassay to about 5 mug per ml. Single radial immunodiffusion in agar is a specific and reproducible assay method, but its sensitivity is also about 5 mug per ml. A radioimmunoassay was established by the Farr technique using purified epidermolysin radiolabeled with 125iodine. This assay was highly reproducible and specific. The staphylococcal products, alpha-toxin and enterotoxins A and B, did not cross-react with anti-epidermolysin antibodies. The sensitivity of the radioimmunoassay is 20 ng per ml.
J Invest Dermatol 1976 Oct
PMID:Measurement of the staphylococcal epidermolytic toxin: a comparison of bioassay, radial immunodiffusion, and radioimmunoassay. 82 70

Substance P is a member of a family of structurally related peptides, called tachykinins, that are involved in the regulation of many biologic processes. Diversity in the generation of multiple tachykinin peptides arises due to multiple genes encoding these peptides as well as by mechanisms of alternative RNA processing and differential posttranslational processing. The multiple peptides are neurotransmitters and/or neuromodulator substances, and they bring about their actions mainly by activating three primary types of receptors, NK-1, NK-2, and NK-3. The pharmacology and tissue locations of these receptor sites are discussed, as is their involvement in certain biologic responses. These three receptor sites have been molecularly characterized by cDNA cloning and functional expression, and all are members of the superfamily of receptors coupled to G-regulatory proteins. Second messenger systems established to be activated by tachykinin receptor stimulation include the hydrolysis of inositol containing phospholipids by a phospholipase C mechanism. The role of substance P in neurogenic inflammation and plasma extravasation is briefly discussed. The generation of new research tools recently in the tachykinin field should allow for a detailed examination of the mechanisms of peptide action, including a focus on receptor structure-function relations and regulation of receptor sensitivity.
J Invest Dermatol 1992 Jun
PMID:Structure, functions, and mechanisms of substance P receptor action. 131 25

Mammalian cells do not live as isolated organisms, but are instead organized into complex, highly specialized tissue organs composed of a homogeneous or a mixed cell population. In order to maintain tissue homeostasis in physiological and pathophysiological conditions, intercellular communication is an absolute requirement. This review will summarize our current knowledge as to how an extracellular signal is transduced via a specific receptor to the interior of the cell and how this signal will induce special cell functions. Attention will be paid to the major signal transduction pathways known to be active in keratinocytes, namely the adenylate cyclase, guanylate cyclase, tyrosine kinase, and phospholipase C systems. Finally, examples will be given of how interactions between these signal transduction pathways can take place and how 'signal cross-talk' might regulate keratinocyte function.
Exp Dermatol 1992 Aug
PMID:Signal transduction pathways in keratinocytes. 136 6

The intracellular inositol pathway is an important route for cell activation and relies on the stimulation of membrane-bound phosphoinositide-specific phospholipase C (PLC). Previously we have shown abnormalities of inositol metabolism in mononuclear cells (MNL) in atopic dermatitis (AD) using an indirect method. We now describe a direct method of measuring PLC activity in membrane and cytosol preparations of MNL in AD. We compare PLC activity in AD with that in normal controls and examine the effect of substrate concentration and nucleotide stimulation on the system. Our findings show increased membrane-bound PLC activity in AD compared with normal controls. Non-specific stimulation of AD PLC activity by nucleotides suggests that the enzyme of atopics is more sensitive to substrate-driven activity than that of non-atopics.
Br J Dermatol 1992 Aug
PMID:Measurement of phosphoinositide-specific phospholipase C activity in mononuclear leucocytes from atopic and normal subjects. 139 Jan 61

Histologic and clinical improvement of sun-exposed skin following topical treatment with retinoic acid has been reported. Daily application of retinoic acid typically results within 2-5 d in an erythematous scaling reaction, which lessens with continued usage. The cellular, immunologic, and biochemical basis of this retinoid reaction and its role in the repair of photodamaged skin are not known. To investigate the retinoid reaction in man, we have treated non-sun-exposed skin with 0.1% retinoic acid cream (Retin-A, Ortho Pharmaceutical Corporation, Raritan, NJ) under occlusion for 4 d to induce erythema and then examined changes in 1) histology, 2) expression of cell-surface molecules, 3) the enzymes and second messengers of the phospholipase C/protein kinase C signal-transduction system, 4) levels of eicosanoids, and 5) levels of interleukin-1 protein and mRNA. These parameters were chosen for measurement both because they are indicators of epidermal function and previous studies suggest they may be responsive to retinoic acid treatment. Epidermal cell growth as judged by increased epidermal thickness and mitotic figures was significantly increased in retinoic acid-treated skin compared to vehicle-treated controls. Increased numbers of CD4+ T cells accompanied by prominence of dermal dendrocytes in the papillary dermis and focal keratinocyte expression of intercellular adhesion molecule-1 were observed in retinoic acid-treated biopsies. Phosphoinositide-specific phospholipase C activity and 1,2-diacylglycerol content were also elevated in retinoic acid-treated epidermis. Protein kinase C activity was reduced by one third in both the soluble and membrane fraction, suggesting down-regulation. Surprisingly, in view of the inflammatory nature of the retinoid reaction, no increases were observed in arachidonic acid, its metabolites, interleukin-1 alpha, or interleukin-1 beta. To examine the specificity of the retinoid reaction, subjects were treated with the irritant sodium lauryl sulfate, under conditions that resulted in a reaction clinically similar to that observed with retinoic acid. The histologic alterations induced by sodium lauryl sulfate were found to be indistinguishable from those induced by retinoic acid. These data indicate that, although a wide range of cellular and molecular alterations occur in retinoic acid-treated skin, these changes may not be necessarily specific or unique for retinoic acid.
J Invest Dermatol 1991 May
PMID:Cellular, immunologic and biochemical characterization of topical retinoic acid-treated human skin. 167 98

Decay-accelerating factor (DAF) is a 70-kD membrane glycoprotein that regulates autologous complement activation, by preventing assembly of alternative or classical C3/C5 convertases, and has been shown to have a wide tissue distribution. In this study, DAF antigen has been demonstrated at the intercellular spaces of normal human epidermis with monoclonal antibody against DAF using the peroxidase-anti-peroxidase method. The amount of DAF was greater at the granular layer than the basal cell layer as judged by intensity of the staining. Western blot analysis of DAF in the epidermis showed a 55-kD band, whereas that of buffy coat cells was approximately 67 kD. When DAF of the epidermis was treated with neuraminidase, the molecular weight was reduced to 53 kD, whereas that of buffy coat cells was 56 kD. These results indicated that the content of sialic acid of DAF in the epidermis was different from that of buffy coat cells. In phosphatidylinositol-specific phospholipase C (PIPLC)-treated normal human skin, DAF was not demonstrated in the epidermis, whereas DAF remained unchanged on the elastic fibers. After the treatment of the epidermis by PIPLC, DAF was released into the buffer shown by Western blot analysis. These results suggested that DAF on the epidermis was anchored to keratinocyte via phosphatidylinositol (PI), whereas the anchoring mechanism of DAF on the elastic fibers was not through PI.
J Invest Dermatol 1991 Jan
PMID:Characterization of decay-accelerating factor (DAF) in human skin. 170 21

Lipocortin I (LPC-I, also called annexin I) is a 35-kD protein that binds phospholipids and actin in a Ca(++)-dependent manner. It is also a major substrate for EGF receptor/kinase and protein kinase C, and a putative inhibitor of phospholipase A2, which produces chemical mediators to cause inflammation. Psoriasis (PS) is an inflammatory skin disease characterized by a rapid turnover of keratinocytes and a defect in keratinization with increased activities of phospholipase C and A2, and EGF receptor. To understand the mechanism of the PS lesion formation and the function of LPC-I, its distribution was studied in the epidermis of PS, subacute eczema and normal skin, and in tumor cells of seborrheic keratosis and Bowen's disease. This study involved immunofluorescence and immunoblotting using affinity-purified polyclonal and monoclonal antibodies specific to LPC-I and to its Ca(++)-bound form. In normal, nonlesional PS and subacute eczema epidermis, LPC-I was detected mainly in the cytoplasm of the suprabasal cells, although it was on the inner aspects of the plasma membrane in some parts of the granular layer. In lesional epidermis of PS, it was localized mainly on the inner aspects of the plasma membrane, but not in the cytoplasm of the whole suprabasal cells as the Ca(++)-bound form, indicating a preferential localization on the plasma membrane. This membrane-binding of LPC-I was also observed in seborrheic keratosis, but not in Bowen's disease. These results suggest that the binding of LPC-I to the plasma membrane occurs actually in living cells, plays a role, not necessarily disease specific, in the PS lesion formation, and has some relevance to normal or abnormal differentiation of keratinocytes.
J Invest Dermatol 1991 Dec
PMID:Lipocortin I (annexin I) is preferentially localized on the plasma membrane in keratinocytes of psoriatic lesional epidermis as shown by immunofluorescence microscopy. 183 17

The phospholipase C (PLC)-mediated hydrolysis of membrane phosphoinositides is an important signal transduction pathway coupled to the cell-surface receptors for several hormones and growth factors. In addition, PLC activity can be modulated by changes in intracellular calcium and activation of GTP binding proteins. In this report, differential activation of PLC in the human keratinocyte cell line SCC-12F was studied as judged by specific patterns of inositol phosphate formation. Several hormones and growth factors previously shown to stimulate PLC in a variety of cell types were screened for activity in SCC-12F cells. Only bradykinin was active, stimulating the PLC-dependent generation of inositol (1,4,5) triphosphate (Ins(1,4,5)P3). Ins(1,4,5)P3 was rapidly metabolized to inositol(1,4)biphosphate (Ins(1,4)P2) and inositol(1,3,4,5)tetrakisphosphate (Ins(1,3,4,5)P4), and subsequently degraded to inositol monophosphates. The response elicited by bradykinin was concentration dependent (EC50 value of 50 nM), suggesting involvement of a specific bradykinin receptor. Treatment of these cells with the calcium ionophore A23187 appeared to result in the direct formation of Ins(1,4)P2 without Ins(1,4,5)P3 as precursor. Treatment of the cells with AIF4-, a putative activator of GTP binding proteins, resulted in the generation of inositol monophosphates as the major metabolites in the absence of detectable Ins(1,4,5)P3 formation. Taken together, these observations suggest that the PLC complex present in SCC-12F cells can be differentially activated to yield either Ins(1,4,5)P3, Ins(1,4)P2, or InsP. The observed effects may be due to a direct PLC-dependent hydrolysis of the appropriate membrane phosphoinositide.
J Invest Dermatol 1991 Jan
PMID:Inositol phosphate formation in the human squamous cell carcinoma line SCC-12 F: studies with bradykinin, the calcium ionophore A23187, and sodium fluoride. 198 86


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