Regulation of arrestin translocation by Ca2+ and myosin III in Drosophila photoreceptors.
J Neurosci
; 32(27): 9205-16, 2012 Jul 04.
Article
em En
| MEDLINE
| ID: mdl-22764229
ABSTRACT
Upon illumination several phototransduction proteins translocate between cell body and photosensory compartments. In Drosophila photoreceptors arrestin (Arr2) translocates from cell body to the microvillar rhabdomere down a diffusion gradient created by binding of Arr2 to photo-isomerized metarhodopsin. Translocation is profoundly slowed in mutants of key phototransduction proteins including phospholipase C (PLC) and the Ca(2+)-permeable transient receptor potential channel (TRP), but how the phototransduction cascade accelerates Arr2 translocation is unknown. Using real-time fluorescent imaging of Arr2-green fluorescent protein translocation in dissociated ommatidia, we show that translocation is profoundly slowed in Ca(2+)-free solutions. Conversely, in a blind PLC mutant with â¼100-fold slower translocation, rapid translocation was rescued by the Ca(2+) ionophore, ionomycin. In mutants lacking NINAC (calmodulin [CaM] binding myosin III) in the cell body, translocation remained rapid even in Ca(2+)-free solutions. Immunolabeling revealed that Arr2 in the cell body colocalized with NINAC in the dark. In intact eyes, the impaired translocation found in trp mutants was rescued in ninaC;trp double mutants. Nevertheless, translocation following prolonged dark adaptation was significantly slower in ninaC mutants, than in wild type a difference that was reflected in the slow decay of the electroretinogram. The results suggest that cytosolic NINAC is a Ca(2+)-dependent binding target for Arr2, which protects Arr2 from immobilization by a second potential sink that sequesters and releases arrestin on a much slower timescale. We propose that rapid Ca(2+)/CaM-dependent release of Arr2 from NINAC upon Ca(2+) influx accounts for the acceleration of translocation by phototransduction.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Visão Ocular
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Cálcio
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Células Fotorreceptoras de Invertebrados
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Cadeias Pesadas de Miosina
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Arrestinas
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Miosina Tipo III
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Proteínas de Drosophila
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Drosophila melanogaster
Limite:
Animals
Idioma:
En
Revista:
J Neurosci
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Reino Unido