Rhodopsin formation in Drosophila is dependent on the PINTA retinoid-binding protein.
Retinoids participate in many essential processes including the initial event in photoreception. 11-cis-retinal binds to opsin and undergoes a light-driven isomerization to all-trans-retinal. In mammals, the all-trans-retinal is converted to vitamin A (all-trans-retinol) and is transported to the retinal pigment epithelium (RPE), where along with dietary vitamin A, it is converted into 11-cis-retinal. Although this cycle has been studied extensively in mammals, many questions remain, including the specific roles of retinoid-binding proteins. Here, we establish the Drosophila visual system as a genetic model for characterizing retinoid-binding proteins. In a genetic screen for mutations that affect the biosynthesis of rhodopsin, we identified a novel CRAL-TRIO domain protein, prolonged depolarization afterpotential is not apparent (PINTA), which binds to all-trans-retinol. We demonstrate that PINTA functions subsequent to the production of vitamin A and is expressed and required in the retinal pigment cells. These results represent the first genetic evidence for a role for the retinal pigment cells in the visual response. Moreover, our data implicate Drosophila retinal pigment cells as functioning in the conversion of dietary all-trans-retinol to 11-cis-retinal and suggest that these cells are the closest invertebrate equivalent to the RPE.
Wang
Tao
T
Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Montell
Craig
C
D000818:Animals; D030801:Animals, Genetically Modified; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D002874:Chromosome Mapping / Q000379:methods; D003001:Cloning, Molecular / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004596:Electroretinography / Q000379:methods; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D005838:Genotype; D017403:In Situ Hybridization / Q000379:methods; D008027:Light; D009154:Mutation; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000235:genetics; D011869:Radioligand Assay / Q000379:methods; D012177:Retinol-Binding Proteins / Q000235:genetics / Q000502:physiology*; D012243:Rhodopsin / Q000378:metabolism*; D016415:Sequence Alignment; D014212:Tretinoin / Q000494:pharmacology
D029721:Drosophila Proteins; D005136:Eye Proteins; C507946:PINTA protein, Drosophila; D012177:Retinol-Binding Proteins; C083315:ninaE protein, Drosophila; D014212:Tretinoin; D012243:Rhodopsin