Autophagy-mediated catabolism of visual transduction proteins prevents retinal degeneration
AUTOPHAGY
Authors: Yao, Jingyu; Jia, Lin; Feathers, Kecia; Lin, Chengmao; Khan, Naheed W.; Klionsky, Daniel J.; Ferguson, Thomas A.; Zacks, David N.
Abstract
Autophagy is a lysosomal degradation pathway critical to preventing the accumulation of cytotoxic proteins. Deletion of the essential autophagy gene Atg5 from the rod photoreceptors of the retina (atg5(rod) mouse) results in the accumulation of the phototransduction protein transducin and the degeneration of these neurons. The purpose of this study is to test the hypothesis that autophagic degradation of visual transduction proteins prevents retinal degeneration. Targeted deletion of both Gnat1 (a gene encoding the subunit of the heterotrimeric G-protein transducin) and Atg5 in the rod photoreceptors resulted in a significantly decreased rate of rod cell degeneration as compared to the atg5(rod) mouse retina, and considerable preservation of photoreceptors. Supporting this we used a novel technique to immunoprecipitate green fluorescent protein (GFP)-tagged autophagosomes from the retinas of the GFP-LC3 mice and demonstrated that the visual transduction proteins transducin and ARR/arrestin are associated with autophagosome-specific proteins. Altogether, this study shows that degradation of phototransduction proteins by autophagy is necessary to prevent retinal degeneration. In addition, we demonstrate a simple and easily reproducible immunoisolation technique for enrichment of autophagosomes from the GFP-LC3 mouse retina, providing a novel application to the study of autophagosome contents across different organs and specific cell types in vivo.
Lutein and zeaxanthin isomers may attenuate photo-oxidative retinal damage via modulation of G protein-coupled receptors and growth factors in rats
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Authors: Sahin, Kazim; Gencoglu, Hasan; Akdemir, Fatih; Orhan, Cemal; Tuzcu, Mehmet; Sahin, Nurhan; Yilmaz, Ismet; Juturu, Vijaya
Abstract
Background: Retina photoreceptor cells are specially adapted for functioning over comprehensive ambient light conditions. Lutein and Zeaxanthin isomers (L/Zi) can protect photoreceptor cells against excessive light degeneration. Efficacy of L/Zi has been assessed on some G protein-coupled receptors (GPCRs), transcription and neurotrophic factors in the retina of rats exposed to incremental intense light emitting diode (LED) illumination conditions. Methods: Forty-two male rats (age: 8 weeks) were randomly assigned to six treatment groups, 7 rats each. The rats with a 3x2 factorial design were kept under 3 intense light conditions (12hL/12hD, 16hL/8hD, 24hL/OhD) and received two levels of L/Zi (0 or 100 mg/kg BW) for two months. Increased nuclear factor-kappa B (NF-kappa B), glial fibrillary acid protein (GFAP), and decreased Rhodopsin (Rho), Rod arrestin (Sag), G Protein Subunit Alpha Transducin1 (Gnat1), neural cell adhesion molecule (NCAM), growth associated protein-43 (GAP43), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and heme oxygenase 1 (HO-1) were observed in 24 h light intensity adaptation followed by 16 h IL and 8 h D. Results: L/Zi administration significantly improved antioxidant capacity and retinal Rho, Rod-arrestin (Sag), Gnat1, NCAM, GAP43, BDNF, NGF, IG1, Nrf2, and HO-1 levels. However, the levels of NF-kappa B and GFAP levels were decreased by administration of L/Zi. Conclusions: According to these results, L/Zi may be assumed as an adjunct therapy to prevent early photoreceptor cell degeneration and neutralize free radicals derived from oxidative stress. (C) 2019 Elsevier Inc. All rights reserved.