Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A brief (30 min) treatment of mouse peritoneal cells (mixture of nonadherent lymphocytes and adherent macrophages) with 1-20 micrograms of lysophosphatidylcholine (lyso-PC) per ml in serum-supplemented RPMI medium 1640, followed by a 3-hr cultivation of the adherent cells alone, results in a greatly enhanced Fc receptor-mediated phagocytic activity of macrophages. This rapid process of macrophage activation was found to require a serum factor, the vitamin D3 binding protein (the human protein is known as group-specific component; Gc). Efficient activation of macrophages was achieved by using medium containing purified human Gc protein. Analysis of intercellular signal transmission among nonadherent (B and T) cells revealed that lyso-PC-treated B cells modify Gc protein to yield a proactivating factor, which can be converted by T cells to the macrophage-activating factor. This rapid generation process of the macrophage-activating factor was also demonstrated by stepwise incubation of Gc protein with lyso-PC-treated B-cell ghosts and untreated T-cell ghosts, suggesting that Gc protein is modified by preexisting membranous enzymes to yield the macrophage-activating factor. Incubation of Gc protein with a mixture of beta-galactosidase and sialidase efficiently generated the macrophage-activating factor. Stepwise incubation of Gc protein with B- or T-cell ghosts and sialidase or beta-galactosidase revealed that Gc protein is modified by beta-galactosidase of B cells and sialidase of T cells to yield the macrophage-activating factor. Administration to mice of a minute amount (4-10 pg per mouse) of in vitro, enzymatically generated macrophage-activating factor resulted in a greatly enhanced (3- to 7-fold) ingestion activity of macrophages.
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PMID:Vitamin D3 binding protein (group-specific component) is a precursor for the macrophage-activating signal factor from lysophosphatidylcholine-treated lymphocytes. 192 12

It has been shown that low concentrations of E. coli lipopolysaccharides (LPS) greatly and selectively stimulate phagocytosis and related functions in mouse bone marrow-derived macrophages. Culture in the presence of 50 ng/ml LPS induced on average a 10-fold enhancement of phagocytosis of IgG-coated sheep erythrocytes. Activation was in two stages--a small increase observed during the first 8 to 12 hr, and the major increase noted between 16 and 24 hr. Phagocytic activity remained at the maximal level for 24 hr and then declined progressively. Stimulation by LPS was dose-dependent; significant effects could be observed at 0.8 ng/ml and the maximum was reached at 10 ng/ml. LPS-treated cells also showed a markedly increased tendency to form colonies. All these effects could be prevented by the addition of 100 ng/ml polymyxin B together with LPS, indicating that the active principle is lipid A. The LPS-dependent increase in phagocytic activity is probably mediated by increased Fc receptor capacity because both parameters were influenced in parallel by the stimulus. Phagocytosis-related events, such as enhanced hexose monophosphate shunt activity, H2O2 formation, and nitroblue tetrazolium reduction were also stimulated by LPS. By contrast, pinocytosis was unaffected. Measurements of cell-associated enzyme activities showed that lactate dehydrogenase, acid phosphatase, and cathepsin D were significantly increased. Beta-glucuronidase, beta-galactosidase, alkaline phosphodiesterase, and aminopeptidase were unchanged and NAD nucleosidase was markedly decreased after LPS treatment. 5'-Nucleotidase and glucosamine uptake were undetectable both in control and LPS-stimulated cells. LPS treatment induced a significant increase in cell-associated protein, but did not result in cell proliferation or increased cell loss as shown by the DNA content that remained constant. LPS-induced changes were dependent on de novo protein synthesis; cycloheximide prevented enhancement of phagocytosis, Fc receptor capacity, and colony formation.
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PMID:Stimulation of phagocytosis in bone marrow-derived mouse macrophages by bacterial lipopolysaccharide: correlation with biochemical and functional parameters. 673 51

Alveolar macrophage (AM) plays important roles in lung homeostasis and pathogenesis of diseases. The study of macrophage gene function and regulation as well as its potential therapeutic intervention will require the development of vectors capable of safe and efficient transfer of DNA to the AM. In the present study, we report a new transfection system that utilizes Fc receptor-mediated endocytosis as a means to target DNA to the AM. This system employs molecular conjugates consisting of a cognate moiety, in this case IgG which recognizes the AM Fc receptor, covalently-linked to a DNA-binding moiety, such as a cationic polyamine. A Complex was formed between immunoglobulin G-polylysine conjugate (IgG-pL) and plasmid DNA carrying the LacZ reporter gene (pSV beta). The conjugate-DNA complex was added directly to the AMs in culture and incubated for 24 h, after which LacZ gene expression was analyzed for beta-galactosidase activity by microfluorometry using a fluorogenic beta-galactosidase substrate, 5-dodecanoylaminofluorescein di-beta-D-galactopyranoside (C12FDG). The AMs treated with the IgG-pL/DNA complex exhibited galactosidase activity significantly augmented over background levels. Effective gene transfer was shown to require both the DNA-binding moiety and cognate moiety for the cell surface receptor. Specific internalization of the complex by the Fc receptor pathway was verified by competitive inhibition using excess IgG. Under this condition, LacZ gene expression was inhibited, suggesting complex internalization through the Fc mediated endocytosis pathway. The requirement of Fc receptors for complex internalization was further demonstrated using cells that lack Fc receptors, e.g., alveolar epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Targeted gene delivery to alveolar macrophages via Fc receptor-mediated endocytosis. 789 36

The contribution to IgG effector function of exposed galactose residues on the oligosaccharide chains in IgG has been tested experimentally. We studied a human monoclonal antibody (BRAD-5) to the Rh D blood group antigen. The preparation used contained a very low percentage of agalactosyl IgG (3.6%). After digestion with beta-galactosidase there was an increase in terminal GlcNAc indicating an increase in % agalactosyl IgG to approximately 30%. Comparison was made of the Fc receptor-(Fc gamma R)-mediated functional interactions of the two glycoforms of BRAD-5 in assays which measured the recognition and destruction of sensitised erythrocytes by various effector cells. After beta-galactosidase treatment, there was a slight reduction in Fc gamma RI-mediated adherence of erythrocytes to U937 cells and phagocytosis of erythrocytes by monocytes. Fc gamma RII-mediated binding of erythrocytes to K562 cells was also reduced. However there was little difference in adherence of erythrocytes to either Daudi cells (via Fc gamma RII) or NK cells (via Fc gamma RIII). There was a consistent reduction in lysis of erythrocytes mediated through Fc gamma RIII on K cells with the beta-galactosidase treated anti-D. Overall the results showed that reduced levels of galactose on IgG anti-D were associated with reduced biological activity in these assays, but the experiments failed to cast light on the physiological role of the agalactosyl glycoform of IgG.
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PMID:The biological activity of human monoclonal IgG anti-D is reduced by beta-galactosidase treatment. 859 27

Neutralization of adenovirus (Ad) by anti-Ad neutralizing antibodies in serum involves formation of Ad-immune complexes that prevent the virus from interacting with target cells. We hypothesized that Ad-immune complexes likely contain viable Ad vectors which, although no longer capable of gaining access to receptors on target cells, may be able to express transgenes in cells bearing Fc receptors for immunoglobulins, i.e., that antibody-based "neutralization" of Ad vectors may be circumvented by the Fc receptor pathway. To test this hypothesis, we expressed the Fcgamma receptor IIA (FcgammaR) in A549 lung epithelial cells or human dermal fibroblasts and evaluated gene transfer in the presence of human neutralizing anti-Ad serum. FcgammaR-expressing cells bound and internalized copious amounts of Ad, with a distinct population of internalized Ad trafficking to the nucleus. The dose-response curves for inhibition of gene transfer revealed that FcgammaR-expressing cells required a more-than-10-fold higher concentration of anti-Ad serum to achieve 50% inhibition of Ad-encoded beta-galactosidase expression compared with non-FcgammaR-expressing cells. The discrepancy between neutralization of Ad during infection of FcgammaR-expressing cells and neutralization of Ad during infection of non-FcgammaR-expressing cells occurred with either heat-inactivated or non-heat-inactivated sera, was blocked by addition of purified Fc domain protein, and did not require the cytoplasmic domain of FcgammaR, suggesting that immune complex internalization proceeded via endocytosis rather than phagocytosis. FcgammaR-mediated infection by Ad-immune complexes did not require expression of the coxsackie virus-Ad receptor (CAR) since similar data were obtained when CAR-deficient human dermal fibroblasts were engineered to express FcgammaR. However, interaction of the Ad penton base with cell surface integrins contributed to the difference in neutralization between FcgammaR-expressing and non-FcgammaR-expressing cells. The data indicate that complexes formed from Ad and anti-Ad neutralizing antibodies, while compromised with respect to infection of non-FcgammaR-expressing target cells, maintain the potential to transfer genes to FcgammaR-expressing cells, with consequent expression of the transgene. The formation of Ad-immune complexes that can target viable virus to antigen-presenting cells may account for the success of Ad-based vaccines administered in the presence of low levels of neutralizing anti-Ad antibody.
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PMID:Neutralized adenovirus-immune complexes can mediate effective gene transfer via an Fc receptor-dependent infection pathway. 1700 1