title: Photoreceptors at a glance.
abstract: Retinal photoreceptor cells contain a specialized outer segment (OS) compartment that functions in the capture of light and its conversion into electrical signals in a process known as phototransduction. In rods, photoisomerization of 11-cis to all-trans retinal within rhodopsin triggers a biochemical cascade culminating in the closure of cGMP-gated channels and hyperpolarization of the cell. Biochemical reactions return the cell to its 'dark state' and the visual cycle converts all-trans retinal back to 11-cis retinal for rhodopsin regeneration. OS are continuously renewed, with aged membrane removed at the distal end by phagocytosis and new membrane added at the proximal end through OS disk morphogenesis linked to protein trafficking. The molecular basis for disk morphogenesis remains to be defined in detail although several models have been proposed, and molecular mechanisms underlying protein trafficking are under active investigation. The aim of this Cell Science at a Glance article and the accompanying poster is to highlight our current understanding of photoreceptor structure, phototransduction, the visual cycle, OS renewal, protein trafficking and retinal degenerative diseases.
authors.affiliation: Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada V5Z 3N9 molday@interchange.ubc.ca.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Molday
authors.affiliation: Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada V5Z 3N9.
authors.forename: Orson L
authors.initials: OL
authors.lastname: Moritz
mesh_terms: D000818:Animals; D006801:Humans; D055537:Light Signal Transduction; D021381:Protein Transport; D012162:Retinal Degeneration / Q000378:metabolism*; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*
keywords: Disk morphogenesis; Photoreceptors; Phototransduction; Protein trafficking; Retinal degenerative diseases; Visual cycle