title: Retrograde intraciliary trafficking of opsin during the maintenance of cone-shaped photoreceptor outer segments of Xenopus laevis.
abstract: Photoreceptor outer segments (OSs) are essential for our visual perception, and take either rod or cone forms. The cell biological basis for the formation of rods is well established; however, the mechanism of cone formation is ill characterized. While Xenopus rods are called rods, they exhibit cone-shaped OSs during the early process of development. To visualize the dynamic reorganization of disk membranes, opsin and peripherin/rds were fused to a fluorescent protein, Dendra2, and expressed in early developing rod photoreceptors, in which OSs are still cone-shaped. Dendra2 is a fluorescent protein which can be converted from green to red irreversibly, and thus allows spatiotemporal labeling of proteins. Using a photoconversion technique, we found that disk membranes are assembled at the base of cone-shaped OSs. After incorporation into disks, however, Opsin-Dendra2 was also trafficked from old to new disk membranes, consistent with the hypothesis that retrograde trafficking of membrane components contributes to the larger disk membrane observed toward the base of the cone-shaped OS. Such retrograde trafficking is cargo-specific and was not observed for peripherin/rds-Dendra2. The trafficking is unlikely mediated by diffusion, since the disk membranes have a closed configuration, as evidenced by CNGA1 labeling of the plasma membrane. Consistent with retrograde trafficking, the axoneme, which potentially mediates retrograde intraflagellar trafficking, runs through the entire axis of OSs. This study provides an insight into the role of membrane reorganization in developing photoreceptor OSs, and proves that retrograde trafficking of membrane cargoes can occur there.
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
authors.forename: Guilian
authors.initials: G
authors.lastname: Tian
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
authors.forename: Kerrie H
authors.initials: KH
authors.lastname: Lodowski
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Lee
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Imanishi
mesh_terms: D000367:Age Factors; D000818:Animals; D030801:Animals, Genetically Modified; D002462:Cell Membrane / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008970:Molecular Weight; D009924:Organ Culture Techniques; D021381:Protein Transport / Q000502:physiology; D012160:Retina / Q000166:cytology* / Q000254:growth & development; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D017299:Rod Opsins / Q000378:metabolism*; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: C583169:Dendra2 protein, Dendronephthya; D008164:Luminescent Proteins; D017299:Rod Opsins
keywords: Dendra2; RRID: AB_2315773; RRID:AB_477585; RRID:nif-0000-30467; cilia; disk membrane; retina; rhodopsin; rod photoreceptor