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)

K1 is a monoclonal antibody that reacts with a cell surface antigen (CAK1) found in human mesothelia and nonmucinous ovarian tumors. In this article, the characteristics of the CAK1 antigen have been examined in detail. Using immunofluorescence microscopy, we have found that the CAK1 signal is removed from the cell surface by treatment with proteases or by phosphatidylinositol-phospholipase C, but not by neuraminidase and beta-galactosidase. The phosphatidylinositol-phospholipase C-released material was found to contain the CAK1 antigen which was detected by a competition radioimmunoassay. The phosphatidylinositol-phospholipase C-released CAK1 antigen was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting and found to be approximately 40 kDa protein. The CAK1-K1 antibody complex remains on the cell surface and is poorly internalized, as shown by an acid wash immunofluorescence internalization assay. An immunotoxin composed of K1 and Lys-PE40, a mutant form of Pseudomonas exotoxin lacking the cell binding domain, was not cytotoxic, supporting the conclusion that the CAK1-K1 antibody complex is not internalized. However, an immunotoxin composed of K1 and native Pseudomonas exotoxin was selectively cytotoxic to cells expressing the CAK1 antigen. This cytotoxicity is due to the fact that domain I of Pseudomonas exotoxin promotes internalization of antigens which are not internalized or bound to antibody alone. Our results suggest that CAK1 is a polypeptide that is expressed on mesothelial cells and many ovarian cancers, and that K1 may be useful as a targeting agent for the immunotherapy of human ovarian cancer.
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PMID:Characterization of the antigen (CAK1) recognized by monoclonal antibody K1 present on ovarian cancers and normal mesothelium. 172 78

A novel cell surface antigen has been identified on a wide range of lymphoid cells and erythrocytes. A mAb YTH 53.1 (CD59) against this antigen enhanced the lysis of human red cells and lymphocytes by homologous complement. Studies of reactive lysis using different species of C56, and of whole serum used as a source of C7-9, indicated that the inhibitory activity of the CD59 antigen is directed towards the homologous membrane attack complex. CD59 antigen was purified from human urine and erythrocyte stroma by affinity chromatography using the mAb YTH 53.1 immobilized on Sepharose, and, following transient expression of a human T cell cDNA library in COS cells, the corresponding cDNA also identified using the antibody. It was found that the CD59 antigen is a small protein (approximately 20 kD as judged by SDS-PAGE, 11.5 kD predicted from the isolated cDNA) sometimes associated with larger components (45 and 80 kD) in urine. The sequence of CD59 antigen is unlike that of other complement components or regulatory proteins, but shows 26% identity with that of the murine LY-6 antigen. CD59 antigen was released from the surface of transfected COS cells by phosphatidylinositol-specific phospholipase C, demonstrating that it is attached to the cell membrane by means of a glycolipid anchor; it is therefore likely to be absent from the surface of affected erythrocytes in the disease paroxysmal nocturnal hemoglobinuria.
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PMID:CD59, an LY-6-like protein expressed in human lymphoid cells, regulates the action of the complement membrane attack complex on homologous cells. 247 70

Several monoclonal antibodies directed against a number of T cell surface molecules are used to elucidate the role of these molecules (cell surface molecules) in T cell activation. The activation of T cells via these molecules are both antigen-dependent (CD3/TcR complex) and antigen-independent. Irrespective of their antigen dependency, these monoclonal antibodies activate T cells by a classical signal transduction pathway, in which the binding of monoclonal antibodies to their cell surface receptors leads to activation of phospholipase C resulting in the depolarization of plasma membrane, hydrolysis of IP2 and IP3 and DAG, the 'second messengers'. IP3 leads to mobilization of intracellular calcium to contribute to an increase in [Ca++]i, whereas DAG causes activation and translocation of PKC and an increasing apparent affinity for Ca++. The role of IP4 in the mobilization of intracellular calcium is emerging. In addition, influx of extracellular calcium also contributes to increase in [Ca++]i. The increase in [Ca++]i following activation via some T cell surface antigen is predominantly due to intracellular mobilization of Ca++ (e.g. CD3/TcR complex), whereas activation via other T cell surface antigen, the increase in [Ca++]i is almost entirely due to an influx of extracellular calcium (e.g. CD5 antigen). All these molecules activate autocrine system of T cell growth, namely IL-2 production, IL-2 receptor expression and T cell proliferation.
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PMID:Mechanisms of transmembrane signalling in human T cell activation. 269 33

The carboxy-terminal amino acid sequence of the soluble form of the 53,000 mol. wt monocyte surface antigen, CD14, was determined by carboxypeptidase Y digestion and compared with the complete amino acid sequence of this protein as predicted from the structure of cloned cDNA [Goyert et al. Science 239, 497-500 (1988)]. The soluble antigen isolated from urine appears to lack eight C-terminal amino acid residues predicted for the full-size translation product, but possesses a major part of the C-terminal hydrophobic domain originally suggested as the membrane-spanning segment. The CD14 antigen can be removed from the monocyte surface by phosphatidylinositol-specific phospholipase C treatment, indicating that this glycoprotein is anchored in the membrane by a phospholipid and is not a transmembrane protein. The soluble form occurring in serum and in supernatants of cultured monocytes thus probably arises by phospholipase-mediated cleaving off the cell surface antigen. A sensitive sandwich ELISA was developed using a monoclonal anti-CD14 antibody, MEM-18, and polyclonal rabbit anti-CD14 antiserum for quantitation of the soluble antigen concns in sera and cell culture supernatants. Using this assay, the antigen present in the supernatant of phospholipase treated peripheral blood mononuclear cells could be estimated. The assay was also used for estimation of the concns of the soluble form of the CD14 antigen in human sera.
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PMID:Structural relationship between the soluble and membrane-bound forms of human monocyte surface glycoprotein CD14. 277 88

To characterize the basis for the cell surface association of processed antigen with the antigen-presenting cell (APC) we analyzed its sensitivity to enzymatic digestion. Antigen-exposed APC that are treated with phospholipase and then immediately fixed lose their ability to stimulate antigen-plus-Ia-specific T-T hybridomas. This effect is seen with highly purified phospholipase A2 and phospholipase C. In addition it is observed with three distinct antigens--ovalbumin, bovine insulin, and poly(LGlu56LLys35LPhe9) [(GluLysPhe)n]. The effect of phospholipases is highly specific. Identically treated APC are equivalent to controls in their ability to stimulate alloreactive hybridomas specific for precisely the same Ia molecule that is corecognized by antigen-plus-Ia-specific hybrids. Furthermore, the antigen-presenting function of enzyme-treated, fixed APC can be reconstituted by the addition of exogenous in vitro processed or "processing independent" antigens. In parallel studies 125I-labeled avidin was shown to specifically bind to APC that were previously exposed and allowed to process biotin-insulin. Biotin-insulin-exposed APC that are pretreated with phospholipase bind significantly less 125I-labeled avidin than do untreated, exposed APC. Identical enzyme treatment does not reduce the binding of avidin to a biotinylated antibody already bound to class II major histocompatibility complex molecules of APC. At least some of the biotin-insulin surface sites are immunologically relevant, because the presentation of processed biotin-insulin by fixed APC is blocked by avidin. This effect is specific. Avidin binding to biotin-insulin-exposed APC does not inhibit allospecific stimulation nor the presentation of unconjugated insulin. These studies demonstrate that phospholipase effectively removes processed cell surface antigen.
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PMID:Characterization of antigen association with accessory cells: specific removal of processed antigens from the cell surface by phospholipases. 346 71

Recent studies of whole animal responses have defined a role for circulating TGF-beta in the preservation and stabilization of microvascular endothelial function (Lefer et al. [1993] Proc. Natl. Acad. Sci. U.S.A., 90:1018-1022; Pfister et al. [1992] J. Exp. Med., 176:265-269). In order to determine which TGF-beta receptor types are responsible for this endothelial cell responsiveness, we used an affinity-labeling technique with 125I-TGF-beta 1 and -beta 2 to characterize TGF-beta receptors on five different endothelial cell cultures: early passage bovine lung and rat epididymal fat pad microvascular endothelial cells (BLMEC and REEC), established endothelial cell lines from bovine adrenal medulla capillaries (EJG), fetal bovine heart (FBHE), and bovine pulmonary artery (CPAE). Since it is known that endothelial cells from different parts of the vasculature vary with respect to cell surface antigen expression (McCarthy et al. [1991] Trends Pharmacol. Sci., 12:462-467; Augustin et al. [1994] Bioessays, 16:901-906), it is important to compare TGF-beta receptor expression on microvascular and macrovascular endothelial cells. We observed 85 kDa and 200-400 kDa labeled receptor bands and analyzed their relationship to the cloned Type II and III receptors using peptide antibodies. We used dithiothreitol and phosphoinositol-phospholipase C pretreatments to establish whether the 65 kDa labeled band which we observed corresponded to the Type I receptor or a glycophosphotidylinositol-linked binding protein. The results demonstrated that microvascular but not macrovascular endothelial cells express high levels of the Type III receptor. This differential expression of the Type III receptor indicates that distinct anatomical segments of the vasculature have distinct TGF-beta receptor profiles. The presence of the Type III receptor on micro- but not macrovascular endothelial cells may account for the reportedly different potency of TGF-beta 1 and TGF-beta 2 on these two endothelial cell types. Analysis of the 85 kDa and 65 kDa affinity-labeled bands revealed that all the endothelial cells express the Type II receptor and a band consistent with the presence of a dithiothreitol-sensitive Type I receptor. Two isoform-specific phosphoinositol-phospholipase C releasable TGF-beta binding proteins were also detected: a 60 kDa protein on one micro- (EJG) and one macro- (FBHE) vascular endothelial cell line and a 150/180 kDa protein on the macrovascular cell lines (FBHE and CPAE). These studies emphasize the heterogeneous nature of endothelial cells and underline the importance of using microvascular endothelial cells when examining TGF-beta responses related to microvascular function.
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PMID:Transforming growth factor-beta receptor expression on endothelial cells: heterogeneity of type III receptor expression. 755 2

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.
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PMID:Pemphigus IgG activates and translocates protein kinase C from the cytosol to the particulate/cytoskeleton fractions in human keratinocytes. 907 78