Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cell surface receptor IgM molecules of cultured human lymlphoblastoid cells (WiL2) patch and redistribute into a cap over the Golgi region of the cell after treatment with multivalent anti-IgM antibodies. During and after the redistribution, ligand-receptor clusters are endocytosed into coated pits and coated vesicles. Morphometric analysis of the distribution of ferritin-labeled ligand at EM resolution reveals the following sequence of events in the endocytosis of cell surface IgM: (a) binding of the multivalent ligand in a diffuse cell surface distribution, (b) clustering of the ligand-receptor complexes, (c) recruitment of clathrin coats to the cytoplasmic surface of the cell membrane opposite ligand-receptor clusters, (d) assembly and (e) internalization of coated vesicles, and (f) delivery of label into a large vesicular compartment, presumably partly lysosomal. Most of the labeled ligand enters this pathway. The recruitment of clathrin coats to the membrane opposite ligand-receptor clusters is sensitive to the calmodulin-directed drug Stelazine (trifluoperazine dihydrochloride). In addition, Stelazine inhibits an alternate pathway of endocytosis that does not involve coated vesicle formation. The actin-directed drug dihydrocytochalasin B has no effect on the recruitment of clathrin to the ligand-receptor clusters and the formation of coated pits and little effect on the alternate pathway, but this drug does interfere with subsequent coated vesicle formation and it inhibits capping. Cortical microfilaments that decorate with heavy meromyosin with constant polarity are observed in association with the coated regions of the plasma membrane and with coated vesicles. SDS-polyacrylamide gel electrophoresis analysis of a coated vesicle preparation isolated from WiL2 cells demonstrates that the major polypeptides in the fraction are a 175-kdalton component that comigrates with calf brain clathrin, a 42-kdalton component that comigrates with rabbit muscle actin and a 18.5-kdalton minor component that comigrates with calmodulin as well as 110-, 70-, 55-, 36-, 30-, and 17-kdalton components. These results clarify the pathways of endocytosis in this cell and suggest functional roles for calmodulin, especially in the formation of clathrin-coated pits, and for actin microfilaments in coated vesicle formation and in capping.
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PMID:Role of coated vesicles, microfilaments, and calmodulin in receptor-mediated endocytosis by cultured B lymphoblastoid cells. 696 16

Antibodies to skeletal muscle actin were produced in rabbits and purified by affinity chromatography. Direct labeling of SDS-PAGE gels of whole cell homogenates from mouse fibroblast cells showed that actin was the only protein detected by these antibodies. Using this immunospecific reagent, we localized actin in cultured fibroblasts using the EGS fixation-permeabilization procedure with the ferritin bridge labeling technique. Swiss 3T3-4 mouse fibroblasts were chosen as an example of highly adherent untransformed cells with prominent microfilament bundles, and L929 mouse fibroblasts were chosen as an example of poorly adherent, rounded, transformed cells with prominent microvilli. Using these two cell types, we have characterized the intracellular distribution of action. Actin was only detected in locations in which morphologically recognizable 60 A microfilaments were found. By both fluorescence and electron microscopy, actin was found in surface ruffles, microvilli, microfilament bundles, the microfilament mat, and the leading lamellae of Swiss 3T3 and L929 cells. In addition, actin was found surrounding micropinosomes and macropinosomes. On the other hand, there was no actin detected around the base of coated pits. Morphometric quantitation showed that almost all the actin was localized in microfilamentous structures. Our results suggest that actin has an important role in cell motility and adhesion, and in the endocytosis of pinosomes, but that actin may not be involved in intracellular processes such as saltatory motion of intracellular organelles.
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PMID:Intracellular localization of actin in cultured fibroblasts by electron microscopic immunocytochemistry. 700 28

Plasma membranes of vertebrate lens fiber cells contain a major intrinsic polypeptide with an apparent molecular weight of 26,000 (MIP26). These plasma membranes are extremely rich in communicating junctions, and it has been suggested that MIP26 is a component of them. MIP26 was purified from cow lenses using preparative SDS gel electrophoresis followed by hydroxylapatite column chromatography. From gel electrophoresis patterns and aggregational properties it was concluded that the MIP26 preparation was homogeneous. The purified MIP26 was used to produce monospecific antibodies in rabbits as assessed by double immunodiffusion and crossed immunoelectrophoresis of purified MIP26 and solubilized lens plasma membranes against the antiserum. Indirect immunocytochemical studies were performed on open and closed lens plasma membrane vesicles by incubation in anti-MIP antiserum followed by ferritin-conjugated goat antirabbit IgG. The conjugate bound unequivocally to lens communicating junctions, indicating that MIP26 is a component of these structures.
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PMID:Immunocytochemical localization of the lens main intrinsic polypeptide (MIP26) in communicating junctions. 703 67

Treatment of rat liver rough microsomes (3.5 mg of protein/ml) with sublytical concentrations (0.08%) of the neutral detergent Triton X-100 caused a lateral displacement of bound ribosomes and the formation of ribosomal aggregates on the microsomal surface. At slightly higher detergent concentrations (0.12-0.16%) membrane areas bearing ribosomal aggregates invaginated into the microsomal lumen and separated from the rest of the membrane. Two distinct classes of vesicles could be isolated by density gradient centrifugation from microsomes treated with 0.16% Triton X-100: one with ribosomes bound to the inner membrane surfaces ("inverted rough" vesicles) and another with no ribosomes attached to the membranes. Analysis of the fractions showed that approximately 30% of the phospholipids and 20-30% of the total membrane protein were released from the membranes by this treatment. Labeling with avidin-ferritin conjugates demonstrated that concanavalin A binding sites, which in native rough microsomes are found in the luminal face of the membranes, were present on the outer surface of the inverted rough vesicles. Freeze-fracture electron microscopy showed that both fracture faces had similar concentrations of intramembrane particles. SDS PAGE analysis of the two vesicle subfractions demonstrated that, of all the integral microsomal membrane proteins, only ribophorins I and II were found exclusively in the inverted rough vesicles bearing ribosomes. These observations are consistent with the proposal that ribophorins are associated with the ribosomal binding sites characteristic of rough microsomal membranes.
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PMID:Recovery of ribophorins and ribosomes in "inverted rough" vesicles derived from rat liver rough microsomes. 706 49

Samples of graded, human lung cancer and of normal lung were assayed for total iron, ferritin, and ferritin iron saturation. Both kinds of tissues contained highly variable amounts of total and ferritin iron and had a range of ferritin iron:protein ratios. No quantitative correlations were found between cancer histopathology and these parameters, in contrast to previous findings for transplantable rat hepatomas. Examination of pooled ferritins isolated from normal lung and lung tumors by quantitative polyacrylamide gel electrophoresis, isoelectric focusing before and after acid-urea dissociation, and SDS electrophoresis, revealed no structural differences. It is concluded that at least for the human lung, malignancy of the kind examined causes no change in ferritin gene expression, and that ferritin assays would not be useful in the grading or detection of human lung cancer.
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PMID:Concentration, structure and iron saturation of ferritins from normal human lung and lung tumors with graded histopathology. 707 83

Anti 5-methyl-cytidine antibodies might be useful agents for the detection and localization of 5-methyl-cytidine of nucleic acids, but only if the antibodies recognize this nucleoside with sufficient specificity. A conjugate containing 18 moles of 5-methyl-cytidine per mole of BSA was prepared and antibodies directed against this nucleoside hapten were produced by immunization of rabbits (as determined by gel diffusion in agar containing excessive amounts of the carrier). A slight crossreaction of cytidine-BSA was eliminated by adsorption on the cross-reacting antigen. Further purification of the antibodies was effected by chromatography on DEAE-Sephadex A-50 and a method for the rapid quantitation of the antibodies showed that 12.7% of the IgG protein are monospecific against 5-methyl-cytidine-BSA. Hydrolysis of antibodies with insolubilized papain produced monovalent Fab fragments which were identified by SDS-Disk-electrophoresis. A two stage method for cross linking the immunoproteins to ferritin by glutaraldehyde was used. The isolation of immunoferritin conjugates by Bio-Gel A 1.5 m column chromatography is described. The identification of the effluents was made by glycerin density gradient ultracentrifugation. The results were visualized by electron microscopy after the treatment of immunoferritin conjugates with (methylated and unmethylated) denaturated DNA, fractionation on the glycerine density gradient, and the spreading by a modification of drop technique.
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PMID:Monospecific antibody against 5-methyl-cytidine for the structural analysis of nucleic acids. 711 47

An experimental approach is described that enables the analysis of interactions between exogenous surface ligands and components of the cytoplasm in neutrophil leukocytes. Neutrophils treated with the nonionic detergent Lubrol PX, under controlled conditions, yield intact detergent-insoluble ghosts. Morphological analysis of neutrophil ghosts shows that they retain the original dimensions of the cell and consist almost entirely of a peripheral filamentous network, representing the submembranous cortical web, concentric to nuclear remnants. All intracellular membrane-bounded organelles, plasma membrane, and background cytoplasmic electron density are absent. Biochemical analysis of the ghosts shows that less than 10% of enzyme markers for the soluble and granule fractions remain, and that greater than 90% of total cell phospholipid is removed during detergent extraction. The major proteins remaining in the ghosts comigrate, on polyacrylamide gels in the presence of SDS, with chicken gizzard actin, myosin, filamin, and a 110-kdalton protein. Patches and caps induced on neutrophils with either fluorescein isothiocyanate-concanavalin A or ferritin-concanavalin A retain their original location and morphology on ghosts after lysis, as determined by both fluorescence and electron microscopy. In similar experiments, but using 125I-labeled lectins, 37% of total cell bound concanavalin A (Con A) and 25% succinylated Con A remain attached to the ghosts. A major 125I-labeled membrane glycoprotein (80 kdaltons) is associated with ghosts prepared from intact neutrophils iodinated in the presence of exogenous lactoperoxidase. Further 125I-labeled membrane glycoproteins (217, 170, and 147 kdaltons) become associated with ghosts prepared from iodinated cells treated before lysis with Con A, but not with succinylated Con A. These data taken together suggest that linkages exist in neutrophils between proteins exposed on the outer surface of the plasma membrane and the peripheral filamentous network independent of the presence of lipid bilayer. The implications of these findings for surface motile phenomena will be discussed.
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PMID:Transmembrane linkage between surface glycoproteins and components of the cytoplasm in neutrophil leukocytes. 719 81

Terminal webs prepared from mouse intestinal epithelial cells were examined by the quick-freeze, deep-etch, and rotary-replication method. The microvilli of these cells contain actin filaments that extend into the terminal web in compact bundles. Within the terminal web these bundles remain compact; few filaments are separated from the bundles and fewer still bend towards the lateral margins of the cell. Decoration with subfragment 1 (S1) of myosin confirmed that relatively few actin filaments travel horizontally in the web. Instead, between actin bundles there are complicated networks of the fibrils. Here we present two lines of evidence which suggest that myosin is one of the major cross-linkers in the terminal web. First, when brush borders are exposed to 1 mM ATP in 0.3 M KCl, they lose their normal ability to bind antimyosin antibodies as judged by immunofluorescence, and they lose the thin fibrils normally found in deep-etch replicas. Correspondingly, myosin is released into the supernatant as judged by SDS gel electrophoresis. Second, electron microscope immunocytochemistry with antimyosin antibodies followed by ferritin-conjugated second antibodies leads to ferritin deposition mainly on the fibrils at the basal part of rootlets. Deep-etching also reveals that the actin filament bundles are connected to intermediate filaments by another population of cross-linkers that are not extracted by ATP in 0.3 M KCl. From these results we conclude that myosin in the intestinal cell may not only be involved in a short range sliding-filament type of motility, but may also play a purely structural role as a long range cross-linker between microvillar rootlets.
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PMID:Organization of actin, myosin, and intermediate filaments in the brush border of intestinal epithelial cells. 720 10

Using a simple procedure, we have isolated a Triton X-100 insoluble protein (58,000 mol wt) from cultured Chinese hamster ovary (CHO) cells, a fibroblastic cell line. The isolated protein, judged homogeneous by two-dimensional gel electrophoresis, was used to elicit antibodies in rabbits. The antiserum obtained is specific for the 58K protein as determined by immunoprecipitation from detergent solubilized 35S-labeled CHO cells and by antibody labeling of SDS solubilized Swiss 3T3 cell extracts separated on a 10% polyacrylamide gel. Indirect immunofluorescence localization with this antiserum in fixed permeabilized Swiss 3T3 cells, whose flat morphology makes them superior for localization studies, reveals filaments that radiate from the perinuclear region to the cell periphery. These filaments were identified as 10 nm filaments by electron microscopic localization using the EGS and ferritin bridge procedures. We conclude that the 58K protein is a major constituent of fibroblast 10 nm filaments. Other intracellular structures were not labeled by this technique.
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PMID:Ultrastructural localization to 10 nm filaments of an insoluble 58K protein in cultured fibroblasts. 739 54

The radula of the limpet, Cellana toreuma, consists of a continuous series of teeth in various stages of iron biomineralization. The major iron-binding protein of the limpet's iron-containing granule (siderosome) has been purified and identified as ferritin. Limpet ferritin has a M(r) of 575 kDa and can be resolved into two bands by SDS-PAGE analysis, with respective M(r)s of 26 and 21 kDa. The partial N-terminal amino acid sequences of these two subunits were confirmed, and antisera against them were respectively generated. The specifity of these two antisera shows no difference between them. By using transmission electron microscopy and immunogold staining techniques the following two events were revealed: (1) in the superior epithelial cell of the radula, ferritin was disassembled through autophagy or heterophagy before exocytosis; (2) of the limpet ferritin, at least the 26-kDa subunit was found to pass through the microvilli, resulting in the accumulation of iron in the extracellular tooth chamber and the formation of goethite needles. Intracellular ferritin being translocated to the extracellular environment is discussed in the text.
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PMID:Translocation of ferritin and biomineralization of goethite in the radula of the limpet Cellana toreuma reeve. 762 30


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