Binding of alpha-2-macroglobulin trypsin complex to human monocytes in culture

Petersen, Claus Munck; Ejlersen, Ejler; Hansen, Peter Wendelboe; Gliemann, Jørgen

doi:10.1080/00365518709168870

Cited by 14 publications

(8 citation statements)

References 25 publications

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“…The present study demonstrates for the first time binding, uptake and degradation of ocrmacroglobulin and pregnancy zone protein-proteinase complexes mediated by high affinity receptors in isolated human hepatocytes. Receptors for oc2-macroglobulin-proteinase complex have earlier been demonstrated in a number of cell types of animal and human origin, including rat and rabbit macrophages [9,[24][25][26], rat hepatocytes [21] and human fibroblasts and monocyte-macrophages [10,12]. The present findings demonstrate that binding of radiolabelled OCrmacroglobulin complex per cell are quantitatively similar in human hepatocytes, cultured human monocytes [II,…”

Section: Discussionsupporting

confidence: 69%

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Human hepatocytes exhibit receptors for α₂‐macroglobulin and pregnancy zone protein‐proteinase complexes

Petersen

Christiansen

Jensen

et al. 1988

Eur J Clin Investigation

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Hepatocytes were isolated by application of the two-step collagenase technique to pieces of human liver. 125I-labelled alpha 2-macroglobulin-trypsin complex bound to hepatocytes at 4 degrees C with a half time of approximately 4.5 h. At near equilibrium half of the receptors were saturated at an alpha 2-macroglobulin-trypsin complex concentration of about 60 pmol 1(-1) and the Scatchard plot was linear. Dissociation of the labelled complex was slow (T1/2 = 24 h) at low receptor occupancies. At high receptor occupancies dissociation was biphasic with a rate constant (K-1) for the initial rapid phase of about 2.4 x 10(-2) min-1. Labelled alpha 2-macroglobulin-trypsin complex bound at 4 degrees C was rapidly internalized at 37 degrees C (T1/2 = 1.9 min), and in 3.5 h approximately 10% of the label was released into the medium in a trichloroacetic acid-soluble form. At 37 degrees C, 125I alpha 2-macroglobulin-trypsin was taken up by hepatocytes and trichloroacetic acid soluble radioactivity appeared in the medium following a sigmoidal curve. Similar results were obtained with 125I-pregnancy zone protein-chymotrypsin complex. At 4 degrees C, hepatocytes bound nearly equal amounts of labelled alpha 2-macroglobulin-trypsin and pregnancy zone protein-chymotrypsin complex, and a large excess (100 nmol 1(-1) of one of the macroglobulins could almost completely abolish binding of trace amounts (5-20 pmol 1(-1] of the other. The present findings strongly suggest that the hepatocyte is of major importance for removal of alpha 2-macroglobulin- and pregnancy zone protein-proteinase complex in humans, in agreement with previous results in rats and mice.

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Section: Discussionsupporting

confidence: 69%

“…High affinity receptors for an <xzM-proteinase complex have been described in a number of animal cell types [8,9] and in human fibroblasts [7,10] and monocyte-macrophages [11,12]. In addition, human fibroblasts [13]and macrophages [14,15] are known to synthesize and secrete <X2M.…”

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confidence: 99%

Human hepatocytes exhibit receptors for α₂‐macroglobulin and pregnancy zone protein‐proteinase complexes

Petersen

Christiansen

Jensen

et al. 1988

Eur J Clin Investigation

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“…However, it is not clear why some cell types, such as T lymphocytes and Jurkat cells, are quite resistant to saporin (Siena et al, 1988;Barbieri et al, 1989;Tazzari et al, 1992b;Cavallaro et al, 1993a), whereas other cell types such as macrophages and U937 cells are very sensitive to this RIP (Barbieri and Stirpe, 1982;Cavallaro et al, 1993a). Neither normal T lymphocytes nor Jurkat cells express a,MR (Petersen et al, 1987), supporting the hypothesis that this receptor mediates saporin entry into the cell. In addition, previous in vivo studies demonstrated liver-specific toxicity induced by saporin and the A chain of ricin, a type I1 RIP (Blakey et al, 1988a,b).…”

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confidence: 71%

α₂‐Macroglobulin Receptor Mediates Binding and Cytotoxicity of Plant Ribosome‐Inactivating Proteins

Cavallaro

Nykjaer

Nielsen

et al. 1995

European Journal of Biochemistry

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It has been proposed that unconjugated type I ribosome-inactivating proteins (RIP) enter cells through passive mechanisms such as fluid-phase pinocytosis. However, some observations, such as the difference in sensitivity to type I RIP among different cell types, and the organ-specific toxicity of type I RIP, indicate a specific mechanism for the entry of these proteins into target cells. The a,-macroglobulin receptor (a,MRj is responsible for the binding and endocytosis of several ligands, including a,-macroglobulidproteinase complexes, plasminogen-activator-inhibitor complexes, apoE-enriched ,&very low density lipoproteins, and lipoprotein lipase. Here we demonstrate that saporin, a potent type I RIP, binds specifically to purified a,MR and the binding is prevented by some a,MR ligands. Moreover, the occupancy of specific ligand-binding sites on cell surface a,MR decreases the cytotoxicity of saporin. The A chain of ricin, a type I1 RIP, also interacts with a,MR. This, and the fact that saporin and ricin A chain both interact also with a,-macroglobulin, indicates a general mechanism of complex interactions between RIP and cellular membranes that is mediated by a,-macroglobulin and the a,MR system.

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“…For experiments, the cells (usually 2 x 106-4 x 106/ml) were incubated at 4 "C or 37 "C in Minisorb tubes (Nunc, Roskilde, Denmark) and kept in suspension by rotating the tubes throughout the experiment. Following 24 h of incubation at 4°C > 95% of LAK cells excluded trypan blue, and > 90% excluded the dye after 4 h at 37 "C. Medium and cells were separated by centrifugation of 200 pI cell suspension on oil [21]. At a concentration of 2 x loh LAK cells/ml this procedure caused 0.17 + 0.07% of the extracellular marker [3H]~glucose to be trapped in the cell pellet.…”

Section: Tnf-a-binding Assaymentioning

confidence: 99%

Bioactive human recombinant tumor necrosis factor‐α: an unstable dimer?

et al. 1989

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As determined by native polyacrylamide gel electrophoresis (PAGE) and gel chromatography the molecular mass of native tumor necrosis factor (TNF)-alpha was approximately 35 kDa. When incubated at low concentrations (less than 1 nM) 125I-labeled TNF-alpha and unlabeled TNF-alpha rapidly multimerized or dissociated into monomers and bioactivity decreased. Sodium dodecyl sulfate (SDS)-PAGE analysis of cross-linked 125I-labeled TNF-alpha demonstrated bands of multi- and trimeric TNF-alpha in addition to dominating bands of dimers and monomers. Tri-, di- and monomeric TNF-alpha were recovered from SDS-PAGE gels and allowed to renature. Of the original receptor-binding activity, 10%-15% was obtained with cross-linked TNF-alpha dimers, whereas none was recovered from preparations of trimeric TNF-alpha. Multimeric and monomeric TNF-alpha exhibited little or no binding activity, and cell-bound, cross-linked TNF-alpha which was dissociated from cellular binding sites was mainly dimeric. 125I-labeled TNF-alpha bound to lymphokine-activated killer (LAK) cells and binding kinetics were much similar (Kd approximately 100 pM) to those reported in other normal cell types. The number of receptors per LAK cell was approximately 4 x 10(3). Cross-linking of TNF-alpha to binding sites in U-937 and LAK cells yielded a receptor-ligand complex of about 80/90 kDa. At 37 degrees C, 125I-labeled TNF-alpha was rapidly internalized and degraded in L-929, U-937 and LAK cells. Degradation of ligand and recycling of receptors were blocked in the presence of methylamine. Methylamine significantly inhibited TNF-alpha-mediated cytolysis of L-929 cells and caused a quantitatively corresponding reduction in cellular TNF-alpha uptake, indicating that L-929 lysis was mediated by receptors.

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Binding of alpha-2-macroglobulin trypsin complex to human monocytes in culture

Cited by 14 publications

References 25 publications

Human hepatocytes exhibit receptors for α₂‐macroglobulin and pregnancy zone protein‐proteinase complexes

Human hepatocytes exhibit receptors for α₂‐macroglobulin and pregnancy zone protein‐proteinase complexes

α₂‐Macroglobulin Receptor Mediates Binding and Cytotoxicity of Plant Ribosome‐Inactivating Proteins

Bioactive human recombinant tumor necrosis factor‐α: an unstable dimer?

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Binding of alpha-2-macroglobulin trypsin complex to human monocytes in culture

Cited by 14 publications

References 25 publications

Human hepatocytes exhibit receptors for α2‐macroglobulin and pregnancy zone protein‐proteinase complexes

Human hepatocytes exhibit receptors for α2‐macroglobulin and pregnancy zone protein‐proteinase complexes

α2‐Macroglobulin Receptor Mediates Binding and Cytotoxicity of Plant Ribosome‐Inactivating Proteins

Bioactive human recombinant tumor necrosis factor‐α: an unstable dimer?

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Product

Resources

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Human hepatocytes exhibit receptors for α₂‐macroglobulin and pregnancy zone protein‐proteinase complexes

Human hepatocytes exhibit receptors for α₂‐macroglobulin and pregnancy zone protein‐proteinase complexes

α₂‐Macroglobulin Receptor Mediates Binding and Cytotoxicity of Plant Ribosome‐Inactivating Proteins