Medical College of Wisconsin
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Biosynthesis and vectorial transport of opsin on vesicles in retinal rod photoreceptors. J Histochem Cytochem 1986 Jan;34(1):5-16 PMID: 2934469

Pubmed ID

2934469

Abstract

Retinal rod photoreceptor cells absorb light at one end and establish synaptic contacts on the other. Light sensitivity is conferred by a set of membrane and cytosol proteins that are gathered at one end of the cell to form a specialized organelle, the rod outer segment (ROS). The ROS is composed of rhodopsin-laden, flattened disk-shaped membranes enveloped by the cell's plasma membrane. Rhodopsin is synthesized on elements of the rough endoplasmic reticulum and Golgi apparatus near the nucleus in the inner segment. From this synthetic site, the membrane-bound apoprotein, opsin, is released from the Golgi in the membranes of small vesicles. These vesicles are transported through the cytoplasm of the inner segment until they reach its apical plasma membrane. At that site, opsin-laden vesicles appear to fuse near the base of the connecting cilium that joins the inner and outer segments. This fusion inserts opsin into the plasma membrane of the photoreceptor. Opsin becomes incorporated into the disk membrane by a process of membrane expansion and fusion to form the flattened disks of the outer segment. Within the disks, opsin is highly mobile, and rapidly rotates and traverses the disk surface. Despite its mobility in the outer segment, quantitative electron microscopic, immunocytochemical, and autoradiographic studies of opsin distribution demonstrate that little opsin is detectable in the inner segment plasma membrane, although its bilayer is in continuity with the plasma membrane of the outer segment. The photoreceptor successfully establishes the polarized distribution of its membrane proteins by restricting the redistribution of opsin after vectorially transporting it to one end of the cell on post-Golgi vesicles.

Author List

Papermaster DS, Schneider BG, DeFoe D, Besharse JC

Author

Joseph C. Besharse PhD Director, Professor in the Ophthalmology and Visual Sciences department at Medical College of Wisconsin




Scopus

2-s2.0-0022631736   56 Citations

MESH terms used to index this publication - Major topics in bold

Animals
Biological Transport
Cell Membrane
Eye Proteins
Freeze Fracturing
Histocytochemistry
In Vitro Techniques
Microscopy, Electron
Photoreceptor Cells
Ranidae
Rod Opsins
Xenopus laevis
jenkins-FCD Prod-353 9ccd8489072cb19f5b9f808bb23ed672c582f41e