Membrane compartmentalization in photoreceptor health and disease

Title: Membrane compartmentalization in photoreceptor health and disease Abstract: Retinal ciliopathies are a group of inherited retina degenerative disorders that currently lack a detailed understanding of their pathological mechanisms. However, it is widely believed that deficiencies in ciliary architecture and protein trafficking specific to cilia are the main culprits behind these disorders. We have developed a method to monitor the trafficking of membrane proteins by specifically labeling newly synthesized proteins and discriminating against old proteins. By using this method in combination with state- of-the-art microscopy, biochemistry, and molecular biology techniques, we propose two Specific Aims: (1) Elucidate the mechanisms regulating rhodopsin compartmentalization in normal and pathological conditions. We aim to test the hypothesis that disruptions in the VxPx motif may lead to the miscoordination of other localization signals, resulting in rhodopsin mistrafficking. Our previous research has shown that rhodopsin contains multiple localization signals that work together with VxPx for proper and efficient ciliary transport. By utilizing affinity purification and mass spectrometry techniques, we will identify rhodopsin-binding partners involved in the trafficking and mistrafficking of rhodopsin. We will then study the roles of these partners in rhodopsin trafficking under both normal and pathological conditions. (2) Elucidate the septin cytoskeleton's role in organizing rod photoreceptors' membrane architecture. Previous study indicates that the OS plasma membrane is segregated into two domains, one for phototransduction and the other for disk synthesis. Furthermore, the OS plasma membrane is segregated from IS plasma membrane. Our recent study suggests that a cytoskeletal element septin is located at the interfaces of these membrane compartments. We will study the contributions of septin to the membrane architecture of rod photoreceptors, both under normal and pathological conditions. Through these studies, we aim to enhance the comprehension of retinal ciliopathies by exploring the structural separation of rod sensory cilia. Additionally, our research aims to uncover new therapeutic options for degenerative disorders of the retina that result from rhodopsin mislocalization. An example would be the inhibition of rhodopsin partners responsible for mistrafficking, as it can effectively alleviate rhodopsin toxicity.