Dissection of the pathway required for generation of vitamin A and for Drosophila phototransduction.
Dietary carotenoids are precursors for the production of retinoids, which participate in many essential processes, including the formation of the photopigment rhodopsin. Despite the importance of conversion of carotenoids to vitamin A (all-trans-retinol), many questions remain concerning the mechanisms that promote this process, including the uptake of carotenoids. We use the Drosophila visual system as a genetic model to study retinoid formation from beta-carotene. In a screen for mutations that affect the biosynthesis of rhodopsin, we identified a class B scavenger receptor, SANTA MARIA. We demonstrate that SANTA MARIA functions upstream of vitamin A formation in neurons and glia, which are outside of the retina. The protein is coexpressed and functionally coupled with the beta, beta-carotene-15, 15'-monooxygenase, NINAB, which converts beta-carotene to all-trans-retinal. Another class B scavenger receptor, NINAD, functions upstream of SANTA MARIA in the uptake of carotenoids, enabling us to propose a pathway involving multiple extraretinal cell types and proteins essential for the formation of rhodopsin.
Wang
Tao
T
Department of Biological Chemistry, Department of Neuroscience, and Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Jiao
Yuchen
Y
Montell
Craig
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000378:metabolism; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism; D051116:Receptors, Scavenger / Q000235:genetics / Q000378:metabolism; D012172:Retinaldehyde / Q000378:metabolism; D012177:Retinol-Binding Proteins / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D051122:Scavenger Receptors, Class B / Q000378:metabolism; D016415:Sequence Alignment; D014785:Vision, Ocular; D014801:Vitamin A / Q000031:analogs & derivatives / Q000378:metabolism*; D019207:beta Carotene / Q000378:metabolism; D050559:beta-Carotene 15,15'-Monooxygenase / Q000378:metabolism
D029721:Drosophila Proteins; C465435:NinaD protein, Drosophila; C507946:PINTA protein, Drosophila; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; D012177:Retinol-Binding Proteins; D051122:Scavenger Receptors, Class B; C493360:ninaB protein, Drosophila; C519704:santa-maria protein, Drosophila; D019207:beta Carotene; D014801:Vitamin A; D012243:Rhodopsin; D050559:beta-Carotene 15,15'-Monooxygenase; D012172:Retinaldehyde