LAUSR

Retinoschisin (RS1) is involved in cell-cell junctions in the retina, but is unique among known celladhesion proteins in that it is a soluble secreted protein. Loss-of-function mutations in RS1 lead to early vision impairment in young males, called X-linked retinoschisis (XLRS). This name refers to the separation of the inner retinal layers, disrupting synaptic signaling. We previously reported the structure to 4.1 Å, revealing double octamer rings [1]. Each 24 kDa subunits has a small N-terminal RS1 domain in the middle of the ring, and a larger C-terminal discoidin domain at the periphery. As a soluble protein, RS1 is unlikely to interact directly with the hydrophobic parts of the cell membrane. Importantly, RS1 binds several sugar moieties, of which the best characterized is galactose [2]. It may tie retinal membranes together through interaction with the abundant glycans found on lipid-embedded and extracellular matrix proteins.