NinaB Is Essential for Drosophila Vision but Induces Retinal Degeneration in Opsin-deficient Photoreceptors
- Publikations-Art
- Zeitschriftenbeitrag (peer-reviewed)
- Autoren
- Olaf Voolstra, Vitus Oberhauser, Emerich Sumser, Nina E. Meyer, Michael E. Maguire, Armin Huber, and Johannes von Lintig
- Erscheinungsjahr
- 2010
- Veröffentlicht in
- J. Biol. Chem.
- Herausgeber
- The American Society for Biochemistry and Molecular Biology, Inc.
- Band/Volume
- 3/285
- Seite (von - bis)
- 2130-2139
In animals, visual pigments are essential for photoreceptor function and survival. These G-protein-coupled receptors consist of a protein moiety (opsin) and a covalently bound 11-cis-retinylidene chromophore. The chromophore is derived from dietary carotenoids by oxidative cleavage and trans-to-cis isomerization of double bonds. In vertebrates, the necessary chemical transformations are catalyzed by two distinct but structurally related enzymes, the carotenoid oxygenase β-carotenoid-15,15′-monooxygenase and the retinoid isomerase RPE65 (retinal pigment epithelium protein of 65 kDa). Recently, we provided biochemical evidence that these reactions in insects are catalyzed by a single enzyme family member named NinaB. Here we show that in the fly pathway, carotenoids are mandatory precursors of the chromophore. After chromophore formation, the retinoid-binding protein Pinta acts downstream of NinaB and is required to supply photoreceptors with chromophore. Like ninaE encoding the opsin, ninaB expression is eye-dependent and is activated as a downstream target of the eyeless/pax6 and sine oculis master control genes for eye development. The requirement for coordinated synthesis of chromophore and opsin is evidenced by analysis of ninaE mutants. Retinal degeneration in opsin-deficient photoreceptors is caused by the chromophore and can be prevented by restricting its supply as seen in an opsin and chromophore-deficient double mutant. Thus, our study identifies NinaB as a key component for visual pigment production and provides evidence that chromophore in opsin-deficient photoreceptors can elicit retinal degeneration.