Mannose 6-phosphate receptors on the plasma membrane on rat retinal pigment epithelial cells. 1988

B I Tarnowski, and V L Shepherd, and B J McLaughlin
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163.

The retinal pigment epithelium (RPE) phagocytizes the tips of photoreceptor outer segments (OS) during normal eye function. It is not known what ligand on OS is recognized by the RPE for removal from the interphotoreceptor matrix. It is possible that a sugar residue on a cell surface glycoconjugate of either the OS or RPE mediates the phagocytic interaction. Pinocytic experiments with a soluble mannose 6-phosphate ligand (125I-labelled mannosidase) showed that similar quantities of ligand were bound by RPE explants from Long Evans rat retinas and from Royal College of Surgeons (RCS/p+) rat retinas known to be defective in the phagocytosis of OS. The addition of mannose 6-phosphate reduced the total counts of bound alpha-mannosidase by 23% in both normal and dystrophic RPE explants. Mannose 6-phosphate receptors were visualized on normal and dystrophic RPE plasma membranes by immunocytochemical techniques. Further, phagocytosis was studied using phosphomannan-coated beads as phagocytic particles. Dystrophic RPE phagocytized phosphomannan-coated beads by a mannose 6-phosphate specific mechanism as shown by a significant reduction in the number of these coated beads taken up in the presence of the competing sugar. In contrast, normal RPE showed no uptake of phosphomannan-coated beads. Our findings indicate that a mannose 6-phosphate receptor is on the apical plasma membrane of rat RPE. This receptor may not be involved in normal OS phagocytic recognition, but may function in the trafficking of lysosomal enzymes by RPE cells.

UI MeSH Term Description Entries
D007150 Immunohistochemistry Histochemical localization of immunoreactive substances using labeled antibodies as reagents. Immunocytochemistry,Immunogold Techniques,Immunogold-Silver Techniques,Immunohistocytochemistry,Immunolabeling Techniques,Immunogold Technics,Immunogold-Silver Technics,Immunolabeling Technics,Immunogold Silver Technics,Immunogold Silver Techniques,Immunogold Technic,Immunogold Technique,Immunogold-Silver Technic,Immunogold-Silver Technique,Immunolabeling Technic,Immunolabeling Technique,Technic, Immunogold,Technic, Immunogold-Silver,Technic, Immunolabeling,Technics, Immunogold,Technics, Immunogold-Silver,Technics, Immunolabeling,Technique, Immunogold,Technique, Immunogold-Silver,Technique, Immunolabeling,Techniques, Immunogold,Techniques, Immunogold-Silver,Techniques, Immunolabeling
D008854 Microscopy, Electron Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen. Electron Microscopy
D008863 Microspheres Small uniformly-sized spherical particles, of micrometer dimensions, frequently labeled with radioisotopes or various reagents acting as tags or markers. Latex Beads,Latex Particles,Latex Spheres,Microbeads,Bead, Latex,Beads, Latex,Latex Bead,Latex Particle,Latex Sphere,Microbead,Microsphere,Particle, Latex,Particles, Latex,Sphere, Latex,Spheres, Latex
D010587 Phagocytosis The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES). Phagocytoses
D010857 Pigment Epithelium of Eye The layer of pigment-containing epithelial cells in the RETINA; the CILIARY BODY; and the IRIS in the eye. Eye Pigment Epithelium
D010873 Pinocytosis The engulfing of liquids by cells by a process of invagination and closure of the cell membrane to form fluid-filled vacuoles. Pinocytoses
D011919 Rats, Inbred Strains Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding. August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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