Eyes shut homolog (EYS) interacts with matriglycan of O-mannosyl glycans whose deficiency results in EYS mislocalization and degeneration of photoreceptors

• Published in: Scientific reports Vol. 10; no. 1; p. 7795
• Main Authors: Liu, Yu, Yu, Miao, Shang, Xuanze, Nguyen, My Hong Hoai, Balakrishnan, Shanmuganathan, Sager, Rachel, Hu, Huaiyu
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 08.05.2020; Nature Publishing Group UK
• Subjects: Amino Acid Sequence; Animals; Cilia; Danio rerio; Extracellular matrix; Eye Proteins - genetics; Eye Proteins - metabolism; Gene Deletion; Glycosylation; Laminin; Localization; Mannose; Matrix protein; Mice; Mutants; Mutation; Photoreceptor Cells - metabolism; Photoreceptors; Polysaccharides; Polysaccharides - metabolism; Protein Transport; Proteins; Retina; Retina - metabolism; Retina - pathology; Retinal degeneration; Retinitis; Retinitis pigmentosa; Secretory vesicles; Secretory Vesicles - metabolism; Survival; Synaptotagmin; Synaptotagmin I - metabolism; Western blotting; Zebrafish; Zebrafish - genetics; Zebrafish - metabolism; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-64752-4

Mutations in eyes shut homolog (EYS), a secreted extracellular matrix protein containing multiple laminin globular (LG) domains, and in protein O-mannose β1, 2-N-acetylglucosaminyl transferase 1 (POMGnT1), an enzyme involved in O-mannosyl glycosylation, cause retinitis pigmentosa (RP), RP25 and RP76, respectively. How EYS and POMGnT1 regulate photoreceptor survival is poorly understood. Since some LG domain-containing proteins function by binding to the matriglycan moiety of O-mannosyl glycans, we hypothesized that EYS interacted with matriglycans as well. To test this hypothesis, we performed EYS Far-Western blotting assay and generated pomgnt1 mutant zebrafish. The results showed that EYS bound to matriglycans. Pomgnt1 mutation in zebrafish resulted in a loss of matriglycan, retention of synaptotagmin-1-positive EYS secretory vesicles within the outer nuclear layer, and diminished EYS protein near the connecting cilia. Photoreceptor density in 2-month old pomgnt1 mutant retina was similar to the wild-type animals but was significantly reduced at 6-months. These results indicate that EYS protein localization to the connecting cilia requires interaction with the matriglycan and that O-mannosyl glycosylation is required for photoreceptor survival in zebrafish. This study identified a novel interaction between EYS and matriglycan demonstrating that RP25 and RP76 are mechanistically linked in that O-mannosyl glycosylation controls targeting of EYS protein.