Immunosubunit ?5i Knockout Suppresses Neovascularization and Restores Autophagy in Retinal Neovascularization by Targeting ATG5 for Degradation.

ABSTRACT:

Purpose

To investigate the functional role of immunoproteasome subunit ?5i in pathologic retinal neovascularization (RNV) and its ability to link the immunoproteasome and autophagy.

Methods

Oxygen-induced retinopathy (OIR) was induced in wild-type (WT) and ?5i knockout (KO) mouse pups on a C57BL/6J background. Proteasome catalytic subunit expression and proteasome activity were evaluated by quantitative real-time PCR (qPCR) and proteasome activity. Retinal vascular anatomy and neovascularization were characterized and quantified by retinal vascular flat-mount staining, fluorescence angiography, platelet endothelial cell adhesion molecule (PECAM) immunostaining, and hematoxylin and eosin staining. Correlation factors, including VEGF and ICAM-1, were detected by qPCR. Autophagy was examined by transmission electron microscopy (TEM). Autophagy biomarkers, including LC3, P62, ATG5, and ATG7, were measured by immunostaining and immunoblotting. The protein interaction between ?5i and ATG5 was detected by immunoprecipitation.

Results

We observed that ?5i had the greatest effect in WT OIR mice. Fundus fluorescence angiography, retinal flat-mount staining, and PECAM staining revealed that pathologic RNV decreased in ?5i KO OIR mice compared with WT OIR mice. Concurrently, TEM, immunostaining, and immunoblotting showed that autophagy was induced in ?5i KO OIR mice compared to WT OIR mice through increases in autophagosome and LC3 expression and a decrease in P62. Mechanistically, ?5i interacted with ATG5 and promoted its degradation, leading to autophagy inhibition and pathogenic RNV.

Conclusions

This study identifies a functional role for ?5i in RNV regulation. ?5i deletion ameliorates RNV and restores autophagy by stabilizing ATG5. These results demonstrate the potential of ?5i to serve as a bridge linking the immunoproteasome and autophagy.

SUBMITTER: Ji L 

PROVIDER: S-EPMC7774061 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature