Adaptations in rod outer segment disc membranes in response to environmental lighting conditions

Abstract

The light-sensing rod photoreceptor cell exhibits several adaptations in response to the lighting environment. While adaptations to short-term changes in lighting conditions have been examined in depth, adaptations to long-term changes in lighting conditions are less understood. Atomic force microscopy was used to characterize the structure of rod outer segment disc membranes, the site of photon absorption by the pigment rhodopsin, to better understand how photoreceptor cells respond to long-term lighting changes. Structural properties of the disc membrane changed in response to housing mice in constant dark or light conditions and these adaptive changes required output from the phototransduction cascade initiated by rhodopsin. Among these were changes in the packing density of rhodopsin in the membrane, which was independent of rhodopsin synthesis and specifically affected scotopic visual function as assessed by electroretinography. Studies here support the concept of photostasis, which maintains optimal photoreceptor cell function with implications in retinal degenerations.

Effect of dietary docosahexaenoic acid on rhodopsin content and packing in photoreceptor cell membranes

“…3). Similar to AFM images of ROS disc membranes reported previously [35–38], ROS disc membranes displayed a characteristic structure of a rim region and lamellar region containing rhodopsin nanodomains, which are formed by oligomeric rhodopsin [33]. Qualitatively, AFM images of ROS disc membranes from the different mouse lines were similar (Fig.…”

“…Mice are normally fed Prolab 3000 diet from LabDiet (St. Louis, MO) in our animal facilities. ROS disc membranes previously investigated by AFM were obtained from mice fed this diet [35, 37, 38]. To establish DHA-deficient and DHA-adequate mouse lines, three generations of mice were fed an ω-3-deficient or ω-3-adequate diets, respectively, and the established lines were maintained on the respective diets.…”

“…Extraction, derivatization, and separation of retinoids by high-performance liquid chromatography (HPLC) were performed on mouse eye samples as described previously [38, 43]. All reactions involving retinoids were carried out under dim red light.…”

“…ROS disc membranes have been imaged using AFM to reveal the organization of oligomeric rhodopsin into nanoscale domains (i.e., nanodomains) [33–36]. The ability to directly monitor the structure of photoreceptor cell membranes and the packing of rhodopsin within those membranes by AFM has revealed the adaptations of photoreceptor cells to changes in rhodopsin expression and environmental lighting conditions [37, 38]. In the current study, AFM was used to assess the changes in photoreceptor cell membranes and rhodopsin packing that accompany changes in DHA levels in the membrane.…”

Loss of PRCD alters number and packaging density of rhodopsin in rod photoreceptor disc membranes

“…to ensure the density of rhodopsin in ROS disc membranes is kept constant, suggesting that regulation of proper rhodopsin density is crucial for photoreceptor disc formation and health 32,33 .…”