title: Arrestin translocation is stoichiometric to rhodopsin isomerization and accelerated by phototransduction in Drosophila photoreceptors.
abstract: Upon illumination, visual arrestin translocates from photoreceptor cell bodies to rhodopsin and membrane-rich photosensory compartments, vertebrate outer segments or invertebrate rhabdomeres, where it quenches activated rhodopsin. Both the mechanism and function of arrestin translocation are unresolved and controversial. In dark-adapted photoreceptors of the fruitfly Drosophila, confocal immunocytochemistry shows arrestin (Arr2) associated with distributed photoreceptor endomembranes. Immunocytochemistry and live imaging of GFP-tagged Arr2 demonstrate rapid reversible translocation to stimulated rhabdomeres in stoichiometric proportion to rhodopsin photoisomerization. Translocation is very rapid in normal photoreceptors (time constant <10 s) and can also be resolved in the time course of electroretinogram recordings. Genetic elimination of key phototransduction proteins, including phospholipase C (PLC), Gq, and the light-sensitive Ca2+-permeable TRP channels, slows translocation by 10- to 100-fold. Our results indicate that Arr2 translocation in Drosophila photoreceptors is driven by diffusion, but profoundly accelerated by phototransduction and Ca2+ influx.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya 466-8601, Japan.
authors.forename: Akiko K
authors.initials: AK
authors.lastname: Satoh
authors.forename: Hongai
authors.initials: H
authors.lastname: Xia
authors.forename: Limin
authors.initials: L
authors.lastname: Yan
authors.forename: Che-Hsiung
authors.initials: CH
authors.lastname: Liu
authors.forename: Roger C
authors.initials: RC
authors.lastname: Hardie
authors.forename: Donald F
authors.initials: DF
authors.lastname: Ready
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D003623:Dark Adaptation / Q000235:genetics; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004596:Electroretinography / Q000379:methods; D004705:Endocytosis / Q000502:physiology; D005786:Gene Expression Regulation / Q000528:radiation effects; D049452:Green Fluorescent Proteins / Q000235:genetics; D007536:Isomerism; D008027:Light; D055537:Light Signal Transduction / Q000235:genetics / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D054799:Phospholipase C beta / Q000235:genetics; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D012243:Rhodopsin / Q000378:metabolism*; D013057:Spectrum Analysis; D013997:Time Factors; D050051:Transient Receptor Potential Channels / Q000235:genetics
chemical_list: C504666:Arr2 protein, Drosophila; D019390:Arrestins; D029721:Drosophila Proteins; D050051:Transient Receptor Potential Channels; D049452:Green Fluorescent Proteins; C013110:metarhodopsins; D012243:Rhodopsin; C468371:NorpA protein, Drosophila; D054799:Phospholipase C beta; D002118:Calcium