scholarly journals Membrane trafficking in the retinal pigment epithelium at a glance

2020 ◽  
Vol 133 (16) ◽  
pp. jcs238279
Author(s):  
Tina Storm ◽  
Thomas Burgoyne ◽  
Clare E. Futter
Keyword(s):  
Retinal Pigment Epithelium ◽  
Membrane Trafficking ◽  
Pigment Epithelium ◽  
Scattered Light ◽  
Retinal Pigment ◽  
Retinal Disease ◽  
Neural Retina ◽  
Photoreceptor Outer Segment ◽  
Waste Products ◽  
Photoreceptor Outer Segments

ABSTRACTThe retinal pigment epithelium (RPE) is a highly specialised pigmented monolayer sandwiched between the choroid and the photoreceptors in the retina. Key functions of the RPE include transport of nutrients to the neural retina, removal of waste products and water from the retina to the blood, recycling of retinal chromophores, absorption of scattered light and phagocytosis of the tips of the photoreceptor outer segments. These functions place a considerable membrane trafficking burden on the RPE. In this Cell Science at a Glance article and the accompanying poster, we focus on RPE-specific adaptations of trafficking pathways. We outline mechanisms underlying the polarised expression of membrane proteins, melanosome biogenesis and movement, and endocytic trafficking, as well as photoreceptor outer segment phagocytosis and degradation. We also briefly discuss theories of how dysfunction in trafficking pathways contributes to retinal disease.

scholarly journals Loss of melanoregulin (MREG) enhances cathepsin-D secretion by the retinal pigment epithelium

2013 ◽  
Vol 30 (3) ◽  
pp. 55-64 ◽  
Author(s):  
LAURA S. FROST ◽  
VANDA S. LOPES ◽  
FRANK P. STEFANO ◽  
ALVINA BRAGIN ◽  
DAVID S. WILLIAMS ◽  
...  
Keyword(s):  
Retinal Pigment Epithelium ◽  
Cathepsin D ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinal Disease ◽  
Protective Role ◽  
Phagocytic Cells ◽  
Phagocytic Capacity ◽  
Photoreceptor Outer Segments ◽  
Age Dependent

AbstractCathepsin-D (Cat-D) is a major proteolytic enzyme in phagocytic cells. In the retinal pigment epithelium (RPE), it is responsible for the daily degradation of photoreceptor outer segments (POSs) to maintain retinal homeostasis. Melanoregulin (MREG)-mediated loss of phagocytic capacity has been linked to diminished intracellular Cat-D activity. Here, we demonstrate that loss of MREG enhances the secretion of intermediate Cat-D (48 kDa), resulting in a net enhancement of extracellular Cat-D activity. These results suggest that MREG is required to maintain Cat-D homeostasis in the RPE and likely plays a protective role in retinal health. In this regard, in the Mregdsu/dsu mouse, we observe increased basal laminin. Loss of the Mregdsu allele is not lethal and therefore leads to slow age-dependent changes in the RPE. Thus, we propose that this model will allow us to study potential dysregulatory functions of Cat-D in retinal disease.

scholarly journals Degradation of Photoreceptor Outer Segments by the Retinal Pigment Epithelium Requires Pigment Epithelium-derived Factor Receptor (PEDF-R)

2021 ◽  
Author(s):  
Jeanee Bullock ◽  
Federica Polato ◽  
Mones Abu-Asab ◽  
Alexandra Bernardo-Colón ◽  
Elma Aflaki ◽  
...  
Keyword(s):  
Retinal Pigment Epithelium ◽  
Phospholipase A2 ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Photoreceptor Outer Segment ◽  
Western Blots ◽  
Rpe Cells ◽  
Photoreceptor Outer Segments ◽  
Transmission Electron ◽  
Bromoenol Lactone

AbstractPurposeTo examine the contribution of PEDF-R to the phagocytosis process. Previously, we identified PEDF-R, the protein encoded by the PNPLA2 gene, as a phospholipase A2 in the retinal pigment epithelium (RPE). During phagocytosis, RPE cells ingest abundant phospholipids and protein in the form of photoreceptor outer segment (POS) tips, which are then hydrolyzed. The role of PEDF-R in RPE phagocytosis is not known.MethodsMice in which PNPLA2 was conditionally knocked out in the RPE were generated (cKO). Mouse RPE/choroid explants were cultured. Human ARPE-19 cells were transfected with siPNPLA2 silencing duplexes. POS were isolated from bovine retinas. The phospholipase A2 inhibitor bromoenol lactone was used. Transmission electron microscopy, immunofluorescence, lipid labeling, pulse-chase experiments, western blots, and free fatty acid and β-hydroxybutyrate assays were performed.ResultsThe RPE of the cKO mice accumulated lipids as well as more abundant and larger rhodopsin particles compared to littermate controls. Upon POS exposure, RPE explants from cKO mice released less β-hydroxybutyrate compared to controls. After POS ingestion during phagocytosis, rhodopsin degradation was stalled both in cells treated with bromoenol lactone and in PNPLA2-knocked-down cells relative to their corresponding controls. Phospholipase A2 inhibition lowered β-hydroxybutyrate release from phagocytic RPE cells. PNPLA2 knock down also resulted in a decline in fatty acids and β-hydroxybutyrate release from phagocytic RPE cells.ConclusionsPEDF-R downregulation delayed POS digestion during phagocytosis. The findings imply that efficiency of RPE phagocytosis depends on PEDF-R, thus identifying a novel contribution of this protein to POS degradation in the RPE.

Cellular Effects of Detachment and Reattachment on the Neural Retina and the Retinal Pigment Epithelium

Retina ◽  
2013 ◽  
pp. 605-617
Author(s):  
Louisa Wickham ◽  
Geoffrey P. Lewis ◽  
David G. Charteris ◽  
Steven K. Fisher
Keyword(s):  
Retinal Pigment Epithelium ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Neural Retina ◽  
Cellular Effects

A PRPH2 gene variant detected in retinitis punctata albescens with congenital hypertrophy of the retinal pigment epithelium

2020 ◽  
pp. 112067212096202
Author(s):  
Aowang Qiu ◽  
Yan Yu ◽  
Junlong Huang ◽  
Qinghuai Liu ◽  
Yannis M Paulus ◽  
...  
Keyword(s):  
Retinal Pigment Epithelium ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Cone Photoreceptor ◽  
Blurred Vision ◽  
Full Field ◽  
Photoreceptor Outer Segments ◽  
Pigmented Lesions ◽  
Retinitis Punctata Albescens ◽  
Congenital Hypertrophy

Retinitis punctata albescens (RPA) is generally diagnosed by the presence of numerous clusters of white punctate lesions in the retina that progress over time and are related to several gene variants. The multifocal variant of congenital hypertrophy of the retinal pigment epithelium (CHRPE) is characterized by multiple, grouped, sharply circumscribed, pigmented spots. The PRPH2 gene encodes a photoreceptor-specific glycoprotein, which is essential for the morphogenesis of rod and cone photoreceptor outer segments. A 39-year-old Chinese female with nyctalopia, complained about blurred vision, presented a unique co-existing feature of RPA and CHRPE. Dilated fundus exam demonstrated numerous porcelain white discrete dots in both eyes and multiple, small, flat clusters of round brown to black pigmented lesions in the left eye. The full field electroretinography (ERG) showed decreased responses after standard dark adaptation and normal b-wave amplitudes after a long (4-h) dark-adapted period. A heterozygous PRPH2 splicing variant was detected in the proband. In addition, the same variant was found in her mother, her son, and her daughter. We describe a PRPH2 variant in a rare case of RPA associated with multifocal CHRPE of the same individual.

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