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)

The interphotoreceptor matrix (IPM) in mammalian retinas is subdivided into rod and cone specific compartments: peanut agglutinin (PNA) binding glycoconjugates are associated with cones, whereas wheat germ agglutinin (WGA) binding glycoconjugates are associated with rods. To establish the identity of a photoreceptor cell type in the human retina with rod dimensions but with a matrix domain which stains with PNA, double label studies, using PNA-ferritin to decorate the extracellular domains and immunocytochemical techniques using a rod specific anti-opsin antibody were conducted. The PNA-binding domains were observed in the cone-associated IPM as well as in the IPM surrounding a small population of rod-shaped photoreceptors. The outer segments of these rod-shaped photoreceptors showed intense labeling with a rod specific anti-opsin antibody as did all other rods which were free of PNA-labeling. A quantitative analysis of all retinal quadrants indicates that this novel rod represents approximately 0.3% of the total rod population in the human retina.
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PMID:Interphotoreceptor matrix in the human retina: cone-like domains surround a small population of rod photoreceptors. 138 87

Glycoconjugates, including glycolipids, glycoproteins, and proteoglycans, are present in the plasma membrane of photoreceptor cells and in the interphotoreceptor matrix surrounding photoreceptor cell ellipsoids and outer segments. Although the precise function of these molecules is unknown, they may be important in mediating photoreceptor-pigment epithelial cell interactions, outer segment membrane assembly, and/or disc shedding. Lectins, affinity ligands for defined carbohydrate sequences, have proven particularly useful in studying the glycoconjugate composition of the interphotoreceptor matrix. The peanut lectin selectively binds to domains of the interphotoreceptor matrix surrounding cone ("cone matrix sheaths"), but not rod inner and outer segments. This is evidence for the existence of chemical and structural heterogeneity within the interphotoreceptor matrix. The studies described herein utilized ultrastructural pre-embedding histochemical labeling to assess whether, in addition to the surrounding interphotoreceptor matrix, peanut lectin binding is associated directly with that plasma membrane of cone inner and outer segments. This study confirms that ferritin-conjugated peanut agglutinin binds to cone matrix sheaths, and, in addition, provides ultrastructural evidence for the presence of binding to the plasma membrane surrounding cone inner and outer segments. The data suggest that cone membrane-associated peanut agglutinin-binding molecules may differ from those located within cone matrix sheaths.
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PMID:Ultrastructural visualization of primate cone photoreceptor matrix sheaths. 337 60

The binding sites of two lectins, peanut agglutinin (PNA) and wheat germ agglutinin (WGA), in the interphotoreceptor matrix (IPM) and photoreceptor plasma membranes of the Japanese monkey (Macaca fuscata) retina were localized using a pre-embedding staining method with ferritin-conjugated (Fer) lectins as well as a postembedding staining method with fluorescence-labeled (FITC) lectins. FITC-PNA, but not WGA, stained cylindrical domains of the IPM around cone outer and inner segments, while the IPM around rods stained with FITC-WGA but not PNA. When the intact (not detached) retinal tissues were incubated with Fer-lectin, the lectin generally labeled neither the IPM nor photoreceptor plasma membranes, but labeled only those structures in detached portions occurring at the edges of occasional retinal tissue blocks. Thus, the neural retinas physically isolated from the retinal pigment epithelium (RPE) were utilized principally here. Ultrastructurally, the IPM in the intact retina consisted of granular and filamentous materials; the IPM in the isolated neutral retina also retained those components, although somewhat loosely organized, and the IPM around cones appeared to be preserved better than did the IPM around rods. Fer-PNA bound to the IPM associated with cones, but not rods; Fer-WGA bound to the rod- but not cone-associated IPM. The ferritin particles were found to lie close to the granular and filamentous materials. Those photoreceptor-associated IPMs extended to the apical surface of the RPE in detached portions or to the apical villi of the RPE which were frequently found in the isolated neural retinas. Also, Fer-PNA labeled the cone, but not rod, plasma membranes; Fer-WGA bound heavily to the plasma membranes of rod and cone outer segments, but sparsely to those of their inner segments. These results suggest that the IPM comprises chemically and physically differential domains specialized for cone and rod photoreceptor cells, and that these specialized IPM are structurally so stable that may be involved in isolating photoreceptor cells physicochemically from each other and in the interactions between the photoreceptors and the RPE, such as retinal adhesion.
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PMID:Specialization of the interphotoreceptor matrices around cone and rod photoreceptor cells in the monkey retina, as revealed by lectin cytochemistry. 342 1

Interstitial retinol binding protein (IRBP) is a soluble glycoprotein found in the interphotoreceptor matrix (IPM) and implicated in shuttling retinol between retina and pigment epithelium (PE) cells. The authors have studied the distribution of IRBP by EM immunocytochemistry. Thin sections of Lowicryl K4M embedded R. pipiens, X. laevis, bovine and human retinas were labeled sequentially with affinity purified rabbit antibovine IRBP, biotinyl-sheep antirabbit F(Ab')2, and avidin-ferritin, or with avidin and biotinyl-ferritin. Antigen was in the interphotoreceptor space and intercalated into the narrow spaces between PE cell microvilli. IRBP penetration between PE cells was delimited abruptly by the PE junctional complexes. IRBP was also observed in small vacuoles in the apical cytoplasm of PE cells and in PE cell phagosomes that contained IRBP surrounding ingested rod tips. IPM was heavily but inhomogeneously labeled. Antigen was usually deposited along the ROS and COS plasma membrane in a confluent layer, but sometimes it was distributed in large (ca. 0.2-micron thick) clumps. In bovine and human retinas, the connecting cilium was ensheathed by antigen at high density but an unlabeled halo surrounded its plasma membrane. The apical plasma membrane of the inner segment aligned along the connecting cilium was also densely coated by antigen. In both frog retinas, the ridges of the periciliary ridge complex (PRC) were coated with antigen. In none of the four species examined was Golgi labeling present. In bovine retinas, labeled vacuoles (granules) in the myoid region were found in very low numbers (15 vacuoles in 358 rod cells). Amphibian retinas also contained only small numbers of myoid vacuoles labeled by anti-IRBP. Absence of antibody binding to intracellular sites of synthesis in any of the cells that abut the interphotoreceptor matrix suggests that the antigen may be masked prior to its release from the synthetic cell(s) or that its level is below limits of detection.
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PMID:Electron microscopic immunocytochemistry of interstitial retinol-binding protein in vertebrate retinas. 348 71

Terminal saccharide sequences in rat photoreceptor cell surface glycoconjugates were characterized. Lectin cytochemistry and electron microscopy were used for preembedding cytochemical localization of surface carbohydrates. Neuraminidase digestion was employed for the exposure of penultimate saccharides in sialoglycoconjugates. Isolated rat retinas were incubated with ferritin-labeled wheat germ agglutinin (WGA), peanut agglutinin (PNA), and soybean agglutinin (SBA) prior to and after neuraminidase digestion. PNA and SBA did not label untreated photoreceptors. WGA densely labeled the photoreceptor surface and interphotoreceptor matrix (IPM) components. Following neuraminidase treatment, PNA, but not SBA, labeled the photoreceptor surface and the IPM. WGA labeling of the IPM was abolished, and the labeling of the photoreceptor surface was reduced. Based on the lectin specificity, it was concluded that photoreceptor surface glycoconjugates in the rat retina contain a terminal trisaccharide: sialic acid-D-galactose-(beta 1----3)-N-acetyl-D-galactosamine.
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PMID:Cytochemical characterization of sialoglycoconjugates on rat photoreceptor cell surface. 355 69

Xenopus laevis interphotoreceptor matrix (IPM) contains a relatively aqueous insoluble wheat germ agglutinin (WGA)-binding component containing unidentified sialoglycoconjugates (Wood et al [1984] J. Comp. Neurol. 228:299-307). The appearance of WGA-binding macromolecules in the IPM was assessed during late embryonic stages (32-45) and in retinal rudiment cultures, using lectin cytochemistry and Western blotting techniques. Metabolic labeling of the neural retina versus retinal pigment epithelium (RPE)-choroid of juvenile Xenopus with 35S-MET was also evaluated in vivo and in vitro. Lectin cytochemistry of eyes from developmental stages 32-42 demonstrated distinct WGA-ferritin-binding sites on the developing outer segment membranes and in the IPM compartment. At stages 44-46 extensive WGA-binding domains were present as an extracellular network with other randomly scattered domains near the retinal pigment epithelium. Retinal rudiments from stage 32-33 were isolated and allowed to differentiate in hanging drop culture (Hollyfield and Witkowsky [1974] J. Exp. Zool. 189:357-377) with or without an investing pigment epithelium. Cultures developing with RPE exhibited an elaborate IPM with an anastomosing meshwork of WGA-ferritin binding sites. In the absence of RPE only limited amounts of binding restricted to the immediate vicinity of the developing photoreceptor outer segment membranes was observed. When Western blots were probed with WGA-HRP, stage 32-45 retinas demonstrated a major WGA-binding band of 126 kD. Similar amounts of WGA-binding macromolecules were synthesized in preparations cultured in the presence or absence of the investing RPE. During development the major WGA-binding component is a 126-kD protein. Equivalent synthesis of this protein in the presence and absence of RPE suggests that the PE is not required for synthesis of this 126-kD component. These results suggest that the retina is the primary site of synthesis of the WGA-binding components of the Xenopus IPM, whereas the PE plays a principal role in their assembly and organization.
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PMID:Development of the interphotoreceptor matrix in Xenopus laevis. 771 7