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

Sci Rep. 2020 May 8;10(1):7795. doi: 10.1038/s41598-020-64752-4.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Eye Proteins / genetics*
  • Eye Proteins / metabolism*
  • Gene Deletion*
  • Glycosylation
  • Mice
  • Mutation
  • Photoreceptor Cells / metabolism*
  • Polysaccharides / metabolism*
  • Protein Transport
  • Retina / metabolism
  • Retina / pathology
  • Secretory Vesicles / metabolism
  • Synaptotagmin I / metabolism
  • Zebrafish / genetics
  • Zebrafish / metabolism
  • Zebrafish Proteins / genetics*
  • Zebrafish Proteins / metabolism*

Substances

  • EYS protein, zebrafish
  • Eye Proteins
  • Polysaccharides
  • Synaptotagmin I
  • Zebrafish Proteins