Retinoids must associate with RBPs, because they are hydrophobic. The critical role for this cycle is reflected by the severe retinal diseases resulting from mutations disrupting two retinal dehydrogenases and two retinoid-binding proteins (RBPs) (for review, see Thompson and Gal, 2003). The 11- cis- retinal is then returned to the rods and cones. A more rapid retinoid cycle leading to regeneration of the cone rhodopsins occurs in the Müller cells ( Mata et al., 2002). Regeneration of the cis-retinal in mammalian rods involves release of the all- trans-retinal from the opsin and formation of vitamin A, which is transported to the retinal pigment epithelium (RPE) and converted into 11- cis-retinal. Light results in a cis-to- trans isomerization of the chromophore, and this transformation represents the only light-driven step during phototransduction. The retinoids required for Drosophila and mammalian phototransduction (3-hydroxy-11- cis-retinal and 11- cis-retinal, respectively) ( Wald, 1968 Vogt and Kirschfeld, 1984 Tanimura et al., 1986) bind to the opsin to form rhodopsin (Rh). In contrast to mammals, the fruit fly, Drosophila melanogaster, appears to require retinoids exclusively in the retina ( Harris et al., 1977). Defects in retinoid levels are associated with many forms of cancer as well as neurodegenerative diseases including retinitis pigmentosa, Parkinson's disease, and Huntington's disease (for review, see Simoni and Tolomeo, 2001 Thompson and Gal, 2003 Mey and McCaffery, 2004). Vitamin A (all- trans-retinol) and other retinoids are critical for processes ranging from development to visual pigment regeneration, neuronal plasticity, and cell proliferation (for review, see Simoni and Tolomeo, 2001 Thompson and Gal, 2003 Mey and McCaffery, 2004). 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. These results represent the first genetic evidence for a role for the retinal pigment cells in the visual response. We demonstrate that PINTA functions subsequent to the production of vitamin A and is expressed and required in the retinal pigment cells. 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. Here, we establish the Drosophila visual system as a genetic model for characterizing retinoid-binding proteins. Although this cycle has been studied extensively in mammals, many questions remain, including the specific roles of retinoid-binding proteins. 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. 11- cis-retinal binds to opsin and undergoes a light-driven isomerization to all- trans-retinal. Replace the cream of coconut with full-fat or low-fat coconut milk for a lighter version.Retinoids participate in many essential processes including the initial event in photoreception.Add more ice for a thicker drink, or more pineapple juice (or less ice) for a thinner version.Make a mocktail with the coco colada or a big-batch virgin piña colada recipe.Switch the rum out for brandy and enjoy a kappa colada.If you can't find a particular rum flavor at the store, make your own rum infusions. Apricot, banana, grapefruit, kiwi, kumquat, orange, passion fruit, and vanilla pair great with both coconut and pineapple. Add a hint of background flavor with a flavored rum.Add ¼-½ ounces of overproof Jamaican rum, such as Smith and Cross, to add an extra kick and an a layer of complexity.It'll make for a fresher, brighter cocktail. Use 5-6 ripe pineapple chunks instead of juice, cut them about 1 inch x 1 inch. Add 1/2 cup crushed ice and mix for 15 seconds, then pour into a 12-ounce glass and garnish with a pineapple and cherry.
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