A retinal proteomics‐based study identifies αA‐crystallin as a sex steroid‐regulated protein

Abstract

Sex steroids influence the structural and functional organization of ocular tissues, promote survival in several pathological conditions including retinal neurodegeneration and have a prominent role in age-related eye diseases as well as neurodegenerative diseases. However, their underlying mechanisms are still elusive. We explored proteomic profiling of rat retinas following intravitreal injection of the bioactive 17β-estradiol or androgen dihydrotestosterone. Using narrow range 2-DE gels and MALDI-TOF-MS analysis, we identified three sex steroid-regulated proteins: the galectin-related-inter-fiber (GRIFIN) which is a galectin family member protein of unknown function, the fatty acid-binding protein epidermal-5 (FABP5) protein responsible for the fatty acid uptake and transport and the small heat shock αA-crystallin (CRYAA) protein involved in preventing aggregation of denatured or unfolded proteins. Changes in the expression of these proteins revealed a predominant estrogenic effect and the multiple CRYAA protein species reflected posttranslational modifications. Sex steroid-mediated modifications of CRYAA were confirmed by Western blotting analysis. This study provides new target proteins for sex steroids with a potential link to age-related diseases associated with proteotoxic stress.

17β-Estradiol Eye Drops Protect the Retinal Ganglion Cell Layer and Preserve Visual Function in an in Vivo Model of Glaucoma

“…In addition, increased oxidative stress-induced retinal degeneration has been associated with decreased levels of α-crystallin expression. 52 Upregulation of a specific isoform of this protein (αA crystallin (Figure 3), has also been obtained upon intravitreal injection of E2, 53 which further supports distribution of the hormone into the retina after topical application as eye drops in our study. CRYAA is a small heat shock protein with chaperone-like activity that prevents the aggregation of denatured or unfolded proteins.…”

The estrogenic retina: The potential contribution to healthy aging and age-related neurodegenerative diseases of the retina

“…Intravitreal injection of E2 may prevent retinal light-induced damage, likely endorsing neurotrophic and anti-inflammatory effects [135]. We found that E2 regulates both transcription and post-transcription of the heat-shock αA-crystallin [134]. αA-crystallin is a chaperone-like protein involved in remodeling cytoskeleton and preventing protein aggregation, inflammation and apoptosis, and with supposed implications in aging, glaucoma, diabetes, Alzheimer and other neurodegenerative diseases (for review, see [136]).…”

“…Diverse proteins, not previously characterized as E2 targets, were identified in an our study on the rat retinal proteomic profiling following intravitreal injection of E2 [134]. Intravitreal injection of E2 may prevent retinal light-induced damage, likely endorsing neurotrophic and anti-inflammatory effects [135].…”

17β-Estradiol Delivered in Eye Drops: Evidence of Impact on Protein Networks and Associated Biological Processes in the Rat Retina through Quantitative Proteomics

“…Our previous studies have convincingly shown that administration of 17β-estradiol (E 2 ) as eye drops can provide therapeutic drug levels in the retina, which was associated with profound protection of retinal ganglion cells and preservation of visual acuity in a rat glaucoma model [20]. However, understanding how the hormone acts in the retina has remained rudimentary, and few estrogen-regulated retinal proteins have been identified to date [21], even relying on early proteomics studies [20,22]. Here, we present an expanded study relying on our previous in vivo experimental design [20], but performed using a newer, more powerful instrument for label-free quantitative proteomic analyses.…”