Rhodopsin formation in Drosophila is dependent on the PINTA retinoid-binding protein

J Neurosci. 2005 May 25;25(21):5187-94. doi: 10.1523/JNEUROSCI.0995-05.2005.

Abstract

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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Blotting, Northern / methods
  • Blotting, Western / methods
  • Chromosome Mapping / methods
  • Cloning, Molecular / methods
  • Dose-Response Relationship, Drug
  • Drosophila / genetics
  • Drosophila / metabolism*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism
  • Drosophila Proteins / physiology*
  • Electroretinography / methods
  • Eye Proteins / genetics
  • Eye Proteins / metabolism
  • Gene Expression Regulation, Developmental / physiology
  • Genotype
  • In Situ Hybridization / methods
  • Light
  • Mutation
  • Pigment Epithelium of Eye / cytology
  • Pigment Epithelium of Eye / metabolism
  • Protein Binding / drug effects
  • Protein Structure, Tertiary / genetics
  • Radioligand Assay / methods
  • Retinol-Binding Proteins / genetics
  • Retinol-Binding Proteins / physiology*
  • Rhodopsin / metabolism*
  • Sequence Alignment
  • Tretinoin / pharmacology

Substances

  • Drosophila Proteins
  • Eye Proteins
  • PINTA protein, Drosophila
  • Retinol-Binding Proteins
  • ninaE protein, Drosophila
  • Tretinoin
  • Rhodopsin