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)

cDNA clones encoding proteins related to the aggrecan/versican family of proteoglycan core proteins have been isolated with antisera against rat brain synaptic junctions. Two sets of overlapping cDNAs have been characterized that differ in their 3'-terminal regions. Northern analyses with probes derived from unique regions of each set were found to hybridize with two brain-specific transcripts of 3.3 and 3.6 kilobases (kb). The 3.6-kb transcript encodes a polypeptide that exhibits 82% sequence identity with bovine brevican and is thought to be the rat ortholog of brevican. Interestingly, the polypeptide deduced from the open reading frame of the 3.3-kb transcript is truncated just carboxyl-terminal of the central domain of brevican and instead contains a putative glypiation signal. Antibodies raised against a bacterially expressed glutathione S-transferase-brevican fusion protein have been used to show that both soluble and membrane-bound brevican isoforms exist. Treatment of the crude membrane fraction and purified synaptic plasma membranes with phosphatidylinositol-specific phospholipase C revealed that isoforms of brevican are indeed glycosylphosphatidylinositol-anchored to the plasma membrane. Moreover, digestions with chondroitinase ABC have indicated that rat brevican, like its bovine ortholog, is a conditional chondroitin sulfate proteoglycan. Immunohistochemical studies have shown that brevican is widely distributed in the brain and is localized extracellularly. During postnatal development, amounts of both soluble and phosphatidylinositol-specific phospholipase C-sensitive isoforms increase, suggesting a role for brevican in the terminally differentiating and the adult nervous system.
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PMID:Brevican, a chondroitin sulfate proteoglycan of rat brain, occurs as secreted and cell surface glycosylphosphatidylinositol-anchored isoforms. 759 78

Brevican is a member of the aggrecan/versican family of proteoglycans. In contrast to the other family members, brevican occurs both as soluble isoforms secreted into the extracellular space and membrane-bound isoforms which are anchored to the cell surface via a glycosylphosphatidylinositol (GPI) moiety. Expression of both variants, which are encoded by two differentially processed transcripts from the same gene, is confined to the nervous system. In the current study, we have used in situ hybridization to examine the cellular sites of synthesis for both mRNAs during postnatal development of the rat brain. Whereas the 3.6-kb transcript encoding secreted brevican displays a widespread distribution in grey matter structures, including cerebellar and cerebral cortex, hippocampus and thalamic nuclei with silver grains accumulating over neuronal cell bodies, the smaller transcript (3.3 kb) encoding GPI-anchored isoforms appears to be largely confined to white matter tracts and diffusely distributed glial cells. This expression pattern is further confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) experiments with RNA from different glial cell cultures, and by biochemical data demonstrating that the crude membrane fraction from isolated optic nerve contains high amounts of phosphatidylinositol-specific phospholipase C (PI-PLC)-sensitive brevican immunoreactivity. During ontogenetic development, both brevican transcripts are generally up-regulated. However, the expression of glypiated brevican is delayed by about 1 week, compared with the expression of the secreted isoform. This late appearance of GPI-linked brevican, its predominant expression in glial cells and its tight association with brain myelin fractions suggest a functional role in neuroglia.
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PMID:Transcripts for secreted and GPI-anchored brevican are differentially distributed in rat brain. 975 Nov 35

The control of chondrocyte-mediated degradation of aggrecan has been studied in rat chondrosarcoma cells and bovine cartilage explants treated with either IL-1 or retinoic acid. The capacity of glucosamine to inhibit the aggrecanase-mediated response (J. D. Sandy, D. Gamett, V. Thompson, and C. Verscharen (1998) Biochem. J. 335, 59-66) has been extended to an investigation of the effect of other hexosamines. Mannosamine inhibits the aggrecanase response to both IL-1 and RA at about one-tenth the concentration of glucosamine in both rat cell and bovine explant systems. This effect of mannosamine appears to be due to its capacity to inhibit the synthesis of glycosylphosphatidylinositol (GPI)-linked proteins by chondrocytes since the GPI synthesis inhibitor 2-deoxyfluoroglucose (2-DFG) also inhibited the aggrecanase response to IL-1b and RA in rat cells. Moreover, phosphatidylinositol-specific phospholipase C (PIPLC) treatment of rat cells markedly inhibited the aggrecanase response to IL-1b and RA. These inhibitory effects of mannosamine, 2-DFG, and PIPLC in rat cells did not appear to be due to an interference with general biosynthetic activity of the cells as measured by [3H]proline incorporation into secreted proteins. We suggest that the aggrecanase response by chondrocytes to IL-1 and RA is dependent on the activity of a GPI-anchored protein on the chondrocyte cell surface.
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PMID:Chondrocyte-mediated catabolism of aggrecan: evidence for a glycosylphosphatidylinositol-linked protein in the aggrecanase response to interleukin-1 or retinoic acid. 1039 42

The secretory lectin ZG16p mediated the binding of aggregated zymogens to the granule membrane in pancreatic acinar cells. Using a recently established in vitro condensation-sorting assay, we now show that pretreatment of zymogen granule membranes (ZGM) with either sodium bicarbonate at pH 10 or with phosphatidyl inositol-specific phospholipase C (PI-PLC) reduced the binding efficiency of zymogens to the same extent, as distinct components were liberated from ZGM. Analysis of the composition of the bicarbonate extract revealed the presence of the secretory lectin ZG16p, the serpin ZG46p and the GPI-linked glycoprotein GP-2, together with several unknown proteins, and small amounts of lipase and carboxylester lipase. The unknown proteins detected in 2-D gels represented a group of acidic and basic protein spots, which were positive in a glycan staining reaction and were soluble in methanol. One protein spot of the acidic group and several of the basic group reacted with a monoclonal antibody directed against chondroitin sulfate, indicating that the proteins represented proteoglycans. A staining pattern similar to the glycan reaction was observed in immunoblots using a polyclonal antibody directed against the whole bicarbonate extract. Immunogold electron microscopy revealed that this antibody reacted with components in the periphery of zymogen granules and strongly stained ZGM in the pellet fraction of a standard in vitro condensation-sorting assay. The amino acid composition of isolated components of both the acidic and basic group showed similarities to aggrecan, a cartilage-specific proteoglycan, and to glycine-rich glycoproteins, respectively. We therefore conclude that a submembranous matrix on the ZGM composed of proteoglycans and glycoproteins is involved in granule formation in pancreatic acinar cells.
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PMID:A submembranous matrix of proteoglycans on zymogen granule membranes is involved in granule formation in rat pancreatic acinar cells. 1082 95

C-terminal truncation of ADAMTS-4 from the p68 form to the p53 form is required for activation of its capacity to cleave the Glu(373)-Ala(374) interglobular domain bond of aggrecan. In transfected human chondrosarcoma cells, this process is not autoproteolytic because the same products form with an inactive mutant of ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin-like motif 4) and truncation is completely blocked by tissue inhibitor of metalloproteinase-1. Instead, activation can be mediated by glycosylphosphatidyl inositol-anchored membrane type 4-matrix metalloproteinase (MT4-MMP, MMP-17) because co-transfection with the active form of MT4-MMP markedly enhanced activation, whereas an inactive mutant of MT4-MMP was ineffective. Treatment of co-transfected cells with phosphatidylinositol-specific phospholipase C liberated the complex of MT4-MMP and p68 ADAMTS4 from the cell membrane, but the p53 ADAMTS4 remained associated. Specific glycosaminoglycan lyase digestions, followed by product analyses using fluorescence-assisted carbohydrate electrophoresis and immunoprecipitation experiments, showed that the p53 form is associated with syndecan-1 through both chondroitin sulfate and heparan sulfate. We conclude that ADAMTS-4 activation in this cell system involves the coordinated activity of both glycosylphosphatidyl inositol-anchored MT4-MMP and the proteoglycan form of syndecan-1 on the cell surface.
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PMID:ADAMTS4 (aggrecanase-1) activation on the cell surface involves C-terminal cleavage by glycosylphosphatidyl inositol-anchored membrane type 4-matrix metalloproteinase and binding of the activated proteinase to chondroitin sulfate and heparan sulfate on syndecan-1. 1470 64

Both clinical and in vitro evidence points to the involvement of the melanocortin peptide, ACTH, in the terminal differentiation of chondrocytes. Terminal differentiation along the endochondral pathway is responsible for linear growth, but also plays a role in osteoarthritic cartilage degeneration. Chondrocyte terminal differentiation is associated with an incremental increase in chondrocyte basal intracellular free calcium ([Ca(2+)](i)), and ACTH agonism of melanocortin receptors is known to mobilize [Ca(2+)](i.) Using differentiated resting chondrocytes highly expressing type II collagen and aggrecan, we examined the influence of both ACTH and dexamethasone treatment on matrix gene transcription and [Ca(2+)](i). Resting chondrocytes treated concurrently with dexamethasone and ACTH expressed matrix gene transcripts in a pattern consistent with that of rapid terminal differentiation. Using the fluorescent Ca(2+) indicator, fura-2, we determined that ACTH evokes transient increases in [Ca(2+)](i) and elevates basal Ca(2+) levels in resting chondrocytes. The transient increases were initiated intracellularly, were abrogated by the phospholipase C-specific inhibitor, U73122, and were partly attenuated by myo-inositol 1,4,5-triphosphate receptor inhibition via 10 mm caffeine. The initial intracellular release also resulted in store-operated calcium entry, presumably through store-operated channels. Dexamethasone priming increased both the initial ACTH-evoked [Ca(2+)](i) release and the subsequent store-operated calcium entry. These data demonstrate roles for ACTH and glucocorticoid in the regulation of chondrocyte terminal differentiation. Because the actions of ACTH are mediated through known G protein-coupled receptors, the melanocortin receptors, these data may provide a new therapeutic target in the treatment of growth deficiencies and cartilage degeneration.
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PMID:Adrenocorticotropin evokes transient elevations in intracellular free calcium ([Ca2+]i) and increases basal [Ca2+]i in resting chondrocytes through a phospholipase C-dependent mechanism. 1580 97

Extracellular calcium-sensing receptors (CaRs) and metabotropic or type B gamma-aminobutyric acid receptors (GABA-B-Rs), two closely related members of family C of the G protein-coupled receptor superfamily, dimerize in the formation of signaling and membrane-anchored receptor complexes. We tested whether CaRs and two GABA-B-R subunits (R1 and R2) are expressed in mouse growth plate chondrocytes (GPCs) by PCR and immunocytochemistry and whether interactions between these receptors influence the expression and function of the CaR and extracellular Ca(2+)-mediated cell differentiation. Both CaRs and the GABA-B-R1 and -R2 were expressed in the same zones of the growth plate and extensively colocalized in intracellular compartments and on the membranes of cultured GPCs. The GABA-B-R1 co-immunoprecipitated with the CaR, confirming a physical interaction between the two receptors in GPCs. In vitro knockout of GABA-B-R1 genes, using a Cre-lox recombination strategy, blunted the ability of high extracellular Ca(2+) concentration to activate phospholipase C and ERK1/2, suppressed cell proliferation, and enhanced apoptosis in cultured GPCs. In GPCs, in which the GABA-B-R1 was acutely knocked down, there was reduced expression of early chondrocyte markers, aggrecan and type II collagen, and increased expression of the late differentiation markers, type X collagen and osteopontin. These results support the idea that physical interactions between CaRs and GABA-B-R1s modulate the growth and differentiation of GPCs, potentially by altering the function of CaRs.
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PMID:Type B gamma-aminobutyric acid receptors modulate the function of the extracellular Ca2+-sensing receptor and cell differentiation in murine growth plate chondrocytes. 1761 48