Identification of the retinoschisin-binding site on the retinal Na/K-ATPase

PLoS One. 2019 May 2;14(5):e0216320. doi: 10.1371/journal.pone.0216320. eCollection 2019.


X-linked juvenile retinoschisis (XLRS) is a hereditary retinal dystrophy, caused by mutations in the RS1 gene which encodes the secreted protein retinoschisin. In recent years, several molecules have been proposed to interact with retinoschisin, including the retinal Na/K-ATPase, L-voltage gated Ca2+ channels, and specific sugars. We recently showed that the retinal Na/K-ATPase consisting of subunits ATP1A3 and ATP1B2 is essential for anchoring retinoschisin to plasma membranes and identified the glycosylated ATP1B2 subunit as the direct interaction partner for retinoschisin. We now aimed to precisely map the retinoschisin binding domain(s) in ATP1B2. In general, retinoschisin binding was not affected after selective elimination of individual glycosylation sites via site-directed mutagenesis as well as after full enzymatic deglycosylation of ATP1B2. Applying the interface prediction tool PresCont, two putative protein-protein interaction patches ("patch I" and "patch II") consisting each of four hydrophobic amino acid stretches on the ATP1B2 surface were identified. These were consecutively altered by site-directed mutagenesis. Functional assays with the ATP1B2 patch mutants identified patch II and, specifically, the associated amino acid at position 240 (harboring a threonine in ATP1B2) as crucial for retinoschisin binding to ATP1B2. These and previous results led us to suggest an induced-fit binding mechanism for the interaction between retinoschisin and the Na/K-ATPase, which is dependent on threonine 240 in ATP1B2 allowing the accommodation of hyperflexible retinoschisin spikes by the associated protein-protein interaction patch on ATP1B2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism*
  • Animals
  • Binding Sites
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Cell Adhesion Molecules / genetics
  • Cell Adhesion Molecules / metabolism*
  • Cell Adhesion Molecules, Neuronal / genetics
  • Cell Adhesion Molecules, Neuronal / metabolism*
  • Eye Proteins / genetics
  • Eye Proteins / metabolism*
  • HEK293 Cells
  • Humans
  • Mice
  • Mice, Knockout
  • Mutagenesis, Site-Directed
  • Retina / metabolism*
  • Sodium-Potassium-Exchanging ATPase / genetics
  • Sodium-Potassium-Exchanging ATPase / metabolism


  • Atp1b2 protein, mouse
  • Cation Transport Proteins
  • Cell Adhesion Molecules
  • Cell Adhesion Molecules, Neuronal
  • Eye Proteins
  • RS1 protein, mouse
  • Adenosine Triphosphatases
  • Atp1a3 protein, mouse
  • Sodium-Potassium-Exchanging ATPase

Grant support

This work was supported by grants FR 3377/1-1 and FR 3377/1-2 to UF; Funder: Deutsche Forschungsgemeinschaft (DFG, Furthermore, it was supported by institutional funds of the Title Group 73 and Title Group 77 (Institute of Human Genetics, University of Regensburg, Germany). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.