Abstract
Purpose :
The connecting cilium (CC) of the photoreceptor provides the only physical route for the trafficking of the outer segment (OS) proteins. Despite the narrowness (~0.3um) of the CC bridge, it resides a wealth of proteins, disruption of which often leads to retinal degeneration. Among these proteins, the role of CC membrane proteins in OS protein trafficking has rarely been addressed. Our investigation aims to understand the role of CC membrane proteins in Rhodopsin
trafficking.
Methods :
Immunohistochemistry was used to determine the CC protein and Rhodopsin localization. Genetically-engineered mutant mice were used to study CC membrane protein function. Protein-protein interactions were detected by pull-down experiment. The ciliary membrane protein complex was analyzed with TAP/MS. Expansion microscopy was conducted to visualize connecting cilium.
Results :
Rhodopsin interacts with several ciliary membrane proteins including Tmem138 and Tmem231. Rhodopsin was detected partially colocalized with Tmem138 and Tmem231 at the CC area during development. Mislocalization of Rhodopsin was observed in Tmem138 mutants before the initiation of the outer segment. Protein interaction and TAP/MS assay identify several types of modified tubulins interacting with Tmem138, which might be involved in Rhodopsin transport.
Conclusions :
Connecting ciliary membrane proteins could facilitate Rhodopsin OS transport by transient interaction with it and coordinating ciliary cytoplasm proteins and microtubules.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.