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)

Human umbilical vein endothelial cells (HUVEC) were found by Western blot analysis to express three membrane-bound C regulatory proteins, decay-accelerating factor (DAF), membrane cofactor protein (MCP) and CD59. DAF was detected on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a 70-kDa molecule under nonreducing conditions in 2% deoxycholate extracts of HUVEC, MCP as a 63-kDa protein and CD59 as a 20-kDa molecule. Northern blot analysis revealed the presence of two species of mRNA expressed in HUVEC, which hybridized to a cDNA probe specific for DAF, with sizes of about 2.0 kb and 2.7 kb. MCP mRNA was detected at 4.2 kb and a CD59 cDNA probe hybridized with three mRNA species with sizes of about 800, 1400 and 2000 bp. DAF and CD59 were released from the surface of HUVEC by phosphatidylinositol-phospholipase C, demonstrating that both are attached to the cell membrane by means of a glycolipid anchor. The relative contribution of DAF, MCP and CD59 in regulating the sensitivity to lysis of HUVEC by autologous complement was determined by incubation of sensitized endothelial cells with F(ab')2 fragments of polyclonal antibodies raised against these proteins. The susceptibility of sensitized cells to lysis by homologous complement was markedly increased in the presence of F(ab')2 anti-CD59 and to a lesser, but significant, extent in the presence of F(ab')2 anti-DAF. F(ab')2 anti-MCP did not significantly alter the susceptibility of HUVEC to complement-mediated lysis.
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PMID:Relative roles of decay-accelerating factor, membrane cofactor protein, and CD59 in the protection of human endothelial cells against complement-mediated lysis. 128 Feb 24

Protectin (CD59) is a complement regulatory protein which blocks the membrane attack complex during complement activation. CD59 was identified on the human sperm surface by means of H19, an IgG1 anti-protectin mouse monoclonal antibody. Using indirect immunofluorescence, flow cytometry and immunoperoxidase, CD59 was found to be present on the whole plasma membrane including the head and tail of fresh ejaculated, capacitated and acrosome-reacted spermatozoa. Immunoperoxidase staining of normal testicular sections indicated that this protein was already present on intraluminal germ cells. Analysis of this sperm protein by gel electrophoresis and immunoblotting revealed that its molecular weight of 20 kDa was comparable to that of CD59 expressed on peripheral blood cells (erythrocytes, lymphocytes) and that it was bound to the membrane through a glycophospholipid tail which could be released after treatment with phosphatidylinositol-specific phospholipase C. Associated to membrane cofactor protein (CD46) and decay accelerating factor (CD55) located in the acrosomal membranes, CD59 may participate to the protection of male gametes against complement-mediated damage as they travel through the female genital tract. Moreover CD59, known as an adhesion molecule involved in lymphocyte rosettes, may also participate in cell to cell adhesion during gametic interaction since H19 inhibited sperm binding and reduced the penetration rate and index during the hamster egg penetration test.
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PMID:Expression of the complement regulatory protein CD59 on human spermatozoa: characterization and role in gametic interaction. 752 80

In previous studies we have demonstrated that mouse Crry/p65 regulates complement component C3 deposition on self membranes, a functional property that both human decay-accelerating factor (DAF) and membrane cofactor protein (MCP) exhibit. We have proposed that Crry/p65 has a similar biologic role in mouse as MCP and perhaps DAF and is the mouse analogue of one or both of these proteins. In order to address this hypothesis and further study Crry/p65, we have prepared rat mAb and a rabbit polyclonal Ab to this protein. Using these reagents we demonstrate that, like human MCP and DAF, the tissue distribution of Crry/p65 is very broad. Most if not all cells of nonneuronal origin express this protein. In addition, by immunohistochemical analysis, Crry/p65 is shown to be more highly expressed in some tissues at potential sites of immune complex deposition and damage, such as the mesangium of the renal glomerulus and the arterial vessel endothelium. By Western blot analysis, protein isoforms can be demonstrated. Unlike human DAF, however, no phosphatidylinositol-specific phospholipase C-sensitive Crry/p65 protein form can be demonstrated on lymphocytes or erythrocytes. Five of six anti-Crry/p65 mAb can partially or completely reverse the capacity of Crry/p65 to block C3 deposition on cell membranes. Analysis of four IgG rat anti-Crry/p65 mAb demonstrates that two major independent epitopes can be detected. Overall, Crry/p65 retains many of the major features of human MCP and DAF, and the use of these reagents should further the understanding of the biologic roles of this class of complement regulatory proteins.
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PMID:Mouse Crry/p65. Characterization of monoclonal antibodies and the tissue distribution of a functional homologue of human MCP and DAF. 769 44

Normal and neoplastic cells are protected from autologous complement (C) attack by different cell-surface C-regulatory proteins including CD59 (protectin), CD46 (membrane cofactor protein) and CD55 (decay-accelerating factor). Indirect immunofluorescence (IIF) analysis showed a differential expression of CD59, CD46, and CD55 in nine human melanoma cell lines and that the expression of CD59 was highly heterogeneous compared with that of CD46 and CD55. Levels of cell membrane CD59 were found to regulate the differential sensitivity of melanoma cells investigated to homologous C-mediated lysis; in fact, an inverse correlation (r > 0.7, p < 0.05) was found between levels of cell membrane CD59, but not of CD46 and CD55, and extent of C-mediated lysis of melanoma cells sensitized with scalar concentrations of the anti-GD3 ganglioside mAb R24. Masking of CD59 by 2.5 micrograms/ml of the anti-CD59 mAb YTH53.1 induced or enhanced C-mediated lysis of melanoma cells sensitized with 2.5 micrograms/ml of mAb R24; the latter phenomenon was found to be directly correlated (r > 0.865, p < 0.01) with levels of cell membrane CD59. CD59 is bound to melanoma cells by a glycosylphosphatidylinositol anchor: treatment of C-resistant melanoma cells Mel 97, by increasing doses of phosphatidylinositol-specific phospholipase C (PI-PLC), progressively decreased cell-surface expression of CD59 and increased C-mediated lysis of cells sensitized with mAb R24. Staining of 38 benign and malignant lesions of melanocytic origin by mAb YTH53.1 demonstrated that CD59 is consistently expressed in vivo and confirmed the heterogeneous expression detected in vitro. Our data, altogether, demonstrate that CD59 is the main restriction factor of C-mediated lysis of melanoma cells and that levels of CD59 may account for their differential resistance to C-mediated lysis. The analysis of the levels of CD59 could represent an useful strategy in selecting melanoma patients who may benefit from immunotherapeutic treatment(s) that trigger C activation.
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PMID:Levels of cell membrane CD59 regulate the extent of complement-mediated lysis of human melanoma cells. 856 95

The vasculature is protected from complement activation by regulatory molecules expressed on endothelial cells. However, complement fixation also occurs on subendothelial extracellular matrix (ECM) in vitro, and is initiated simply by retraction or removal of overlying cells. To investigate mechanisms controlling vascular complement activation, we examined subendothelial ECM for the presence of complement regulatory proteins. Decay-accelerating factor (DAF) was found on both human umbilical vein endothelial cells (HUVEC) and in their ECM; in contrast, membrane cofactor protein was found only on cells. ECM and HUVEC DAF were distinguishable based on several properties. While HUVEC DAF is anchored to cell membranes by a phospholipase C-sensitive glycosylphosphatidylinositol linkage. DAF was removed from ECM only by proteolytic digestion. Cytokines (TNF-alpha, IL-1 beta, IL-4) increased HUVEC DAF expression, but had minimal effect on ECM DAF; in contrast, phorbol 12-myristate 13-acetate (PMA) and wheat germ agglutinin markedly increased DAF on both HUVEC and ECM. The effect of PMA was mediated by activation of protein kinase C. The complement regulatory potential of ECM DAF was assessed by evaluating the effect of DAF-neutralizing antibodies on C3 deposition on HUVEC ECM, as well as on HeLa cell ECM, which had a considerably higher DAF content. DAF blockade enhanced C3 deposition on HeLa ECM, but had no effect on HUVEC ECM. As ECM DAF is likely to be immobile, i.e. able to interact only with C3 convertases forming in the immediate vicinity, its ability to regulate complement activation may be particularly density dependent, and contingent on endothelial-dependent up-regulation.
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PMID:Decay-accelerating factor is a component of subendothelial extracellular matrix in vitro, and is augmented by activation of endothelial protein kinase C. 954 1

Human lung cancer expresses cell membrane complement inhibitory proteins (CIP). We investigated whether human lung cancer cell lines also express cell-membrane CIP molecules and whether the biology of CIP molecules in these cell lines differs from that of CIP in normal human respiratory epithelium in culture. The cell lines ChaGo K-1 and NCI-H596 were compared with normal human nasal epithelium in primary cultures in respect to the level of cell membrane CIP expression of membrane cofactor protein (MCP; CD46), decay-accelerating factor (DAF; CD55) and CD59, in respect to the level of cell resistance to complement-mediated lysis, and in respect to the contribution of cell membrane CIP to cell resistance against complement-mediated lysis. We found, using flow cytometry, that both human lung cancer cell lines expressed MCP, DAF and CD59, as did normal nasal epithelial cells. However, normal cells showed a large subpopulation of low DAF-expressing cells (60% of all cells) and a smaller subpopulation of high DAF-expressing cells (40%), while the lung cancer cell lines showed only one cell population, of high DAF expression. In addition, both lung cancer cell lines expressed higher MCP levels, and NCI-H596 cells showed higher levels of CD59. Cell resistance to complement-mediated lysis of both lung cancer cell lines was much higher than that of normal cells. Fifty percent normal human serum, under the same concentrations of complement activators, induced lysis of less than a mean of 10% of lung cancer cells, while lysing up to a mean of 50% of nasal epithelial cells. Lung cancer cell resistance to complement was due to its ability to prevent significant activation of complement upon its cell membrane, as manifested by a failure of complement activators to increase cell membrane deposition of C3-related fragments. The exact mechanism for this resistance remains obscure. Unexpectedly, neutralizing antibodies, anti-MCP and anti-DAF were entirely ineffective and anti-CD59 was only slightly effective (18% mean cell lysis) in increasing the susceptibility of the lung cancer cell lines to complement, while the same antibodies were very effective in facilitating complement-mediated lysis of the normal nasal epithelial cells (50% mean cell lysis with CD59 MoAb). On the other hand, detachment of DAF and CD59 by phosphatidylinositol-specific phospholipase C (PIPLC) from the lung cancer cell lines abrogated their resistance to lysis. We suggest that the biology of cell membrane CIP molecules in human lung cancer cell lines is different from that of CIP in normal respiratory epithelial cells. Human lung cancer cell lines are able to prevent significant complement activation upon its cell membrane and are therefore especially resistant to complement-mediated lysis. Complement resistance may serve this common and highly lethal human cancer as an escape mechanism from the body's immunosurveillance and prevent effective immunotherapy with tumour-specific MoAbs.
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PMID:Human lung cancer cell lines express cell membrane complement inhibitory proteins and are extremely resistant to complement-mediated lysis; a comparison with normal human respiratory epithelium in vitro, and an insight into mechanism(s) of resistance. 971 65