Abstract
Purpose :
Serpin family E member 3 (SERPINE3) is a putative serine proteinase inhibitor with unknown function in mammalian retina. Here, we define the cellular expression of SERPINE3 in human and mouse, define target proteases, and explore its function in a novel mouse model.
Methods :
Human and macaque expression data from eyeIntegration and plae were analyzed. Protease assay using fluorescently-labeled peptide substrate was performed for screening the SERPINE3 against all major classes of proteases. Serpine3-VenusGFP knockin mice were generated using CRISPR-mediated homologous recombination in mouse zygotes, replacing exon 2 with a Venus reporter. For analyzing the retinal degeneration of Serpine3Gfp/Gfp mice, hematoxylin and eosin staining, anti-ZO1 staining and anti-photoreceptor specific markers’ immunostaining were performed.
Results :
SERPINE3 is specifically expressed in human and macaque retinal pigment epithelium (RPE). Through compartment analysis, SERPINE3 protein was observed in cytoplasm and extracellular vesicles of human iPSC-derived RPE. Protease inhibition screen of 75 candidates identified Caspase 1, Caspase 2, Caspase 5, and Cathepsin K as putative SERPINE3 targets. In mouse eye, Serpine3 protein and Serpine3-VenusGFP reporter expression were localized exclusively to RPE. Serpine3Gfp/Gfp homozygous mice are viable. Preliminary assessment indicates regional structural abnormalities of the outer retina and retinal-RPE interface.
Conclusions :
In mammalian retina, SERPINE3 is expressed specifically in the RPE and is secreted in extracellular vesicles. SERPINE3 targets include multiple caspases implicated in retinal inflammation and cell death. Deletion of Serpine3 in mouse results in structural retinal abnormalities, supporting a nonautonomous role for RPE-secreted Serpine3 in outer nuclear lamination.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.