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XB-ART-49055
J Comp Neurol November 1, 2014; 522 (16): 3577-3589.

Retrograde intraciliary trafficking of opsin during the maintenance of cone-shaped photoreceptor outer segments of Xenopus laevis.

Tian G , Lodowski KH , Lee R , Imanishi Y .


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.

PubMed ID: 24855015
PMC ID: PMC4142104
Article link: J Comp Neurol
Grant support: R01 EY020826 NEI NIH HHS , DK007319 NIDDK NIH HHS , EY011373 NEI NIH HHS , EY020826 NEI NIH HHS , P30 EY011373 NEI NIH HHS , T32 DK007319 NIDDK NIH HHS

Genes referenced: cnga1 prph prph2


Article Images: [+] show captions
References:
Anderson, 1978, Pubmed [+]


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