Roles of Disulfide Bonds for Outer Segment Disc Rim Curvature

The protein peripherin-2/rds (P/rds) is a protein located within the photoreceptor cells (rods and cones) of the eye and is essential to vision. P/rds is an integral membrane protein that is required to form outer segments organelles, and is assembled as polymers that are joined by disulfide bonds. Outer segments contain stacks of discs with highly curved, hairpin like rims and it is still unknown how these rims attain their highly specific shape. To determine if the disulfide bonds that hold together P/rds higher order polymers are responsible for the shaping of these membranes, Mus musculus (mouse) and Xenopus leavis (frog) eye cups were treated ex vivo with a disulfide reducing agent and analyzed by western blotting and transmission electron microscopy. It was determined that outer segment discs treated in this way possessed rim diameters 25% greater in size (in comparison to control rims) in both species. This treatment was effective at reducing P/rds, so we conclude that there is a correlation between disulfide bond reduction between P/rds polymer constituents and the increase in outer segment disc rim size and shape change.