Stargardt-like macular dystrophy (STGD3) is a dominantly inherited juvenile macular degeneration that eventually leads to loss of vision. Three independent mutations causing STGD3 have been identified in exon six of a gene named Elongation of very long chain fatty acids 4 (ELOVL4). The ELOVL4 protein was predicted to be involved in fatty acid elongation, although evidence for this and the specific step(s) it may catalyze have remained elusive. Here, using a gain-of-function approach, we provide direct and compelling evidence that ELOVL4 is required for the synthesis of C28 and C30 saturated fatty acids (VLC-FA) and of C28-C38 very long chain polyunsaturated fatty acids (VLC-PUFA), the latter being uniquely expressed in retina, sperm, and brain. Rat neonatal cardiomyocytes and a human retinal epithelium cell line (ARPE-19) were transduced with recombinant adenovirus type 5 carrying mouse Elovl4 and supplemented with 24:0, 20:5n3, or 22:5n3. The 24:0 was elongated to 28:0 and 30:0; 20:5n3 and 22:5n3 were elongated to a series of C28-C38 PUFA. Because retinal degeneration is the only known phenotype in STGD3 disease, we propose that reduced VLC-PUFA in the retinas of these patients may be the cause of photoreceptor cell death.fatty acid biosynthesis ͉ macular degeneration T hree independent mutations in the last exon (exon-VI) of the ELOVL4 gene are associated with dominant Stargardt-like macular dystrophy (STGD3) in humans (1-4). These mutations cause a frame-shift that introduces a stop codon, resulting in premature termination of the protein and removal of the signal sequence for targeting the protein to its putative cellular location, the endoplasmic reticulum (1, 4). As a result, the mutant protein mis-localizes and aggregates (3,5,6), and, when coexpressed with the wild type protein, the mutant and wild-type proteins associate and mis-localize (3, 7). Based on sequence homology with a group of functional yeast genes and other mammalian ELOVLs, the ELOVL4 protein was predicted to be involved in elongation of very long chain fatty acids (1,5,8). For example, the yeast microsomal Elo1p is responsible for elongation of carbon chains between 14:0 and 16:0 (9). Yeast Elo2p and Elo3p, and mammalian ELOVL1, 2, 3, and 5 have been shown to be involved in elongation of saturated, monounsaturated, or polyunsaturated fatty acids (PUFA) from 18 to 26 carbons (10-12). However, a role for ELOVL4 protein in fatty acid elongation and the specific step(s) it may catalyze have remained elusive (13,14). Based on the abundant expression of ELOVL4 protein in photoreceptor cells of the retina (15-17) and to lesser extents in brain, testis, and skin (17), it was first hypothesized that ELOVL4 may be involved in the biosynthetic pathway of docosahexaenoic acid (22:6n3, DHA), the most abundant PUFA in the retina and the brain (1,16,18). A series of experiments carried out in our laboratory (unpublished data) does not support this hypothesis.Recent reports establish ELOVL4 as an essential protein for growth and development, as neonatal ...

This article is available online at http://www.jlr.org tively rare compared with the abundance of FA containing 16-22 carbons, they are widely distributed in higher plants and animals ( 1-10 ). They are found in most living organisms from humans to autotrophic and heterotrophic lower organisms, including microalgae, sponges, bacteria, and fungi ( 1,9,(11)(12)(13)(14)(15). VLC-FA are found mainly in seed oils, plant waxes, cutin, suberin, skin, hair, and wax glands ( 1 ), whereas VLC-PUFA are found primarily in retina, brain ( 1, 16 ), testis, and spermatozoa ( 17-19 ).The unusually long hydrocarbon chains with 3 -9 double bonds, which are prone to oxidative damage, combined with the small quantities found in mammalian tissues, have made them diffi cult to isolate and analyze in detail over the years ( 9 ). Very little is therefore known about the metabolism and function of VLC-PUFA and VLC-FA in mammals, except for their increase in disorders of peroxisomal function ( 3,16,20,21 ), as components of the secretions of meibomian glands (22)(23)(24)(25)(26)(27), and their reduction in animal models of autosomal dominant Stargardt-like macular dystrophy (STGD3) ( 28-32 ), a juvenile form of macular degeneration. In contrast, the roles of long-chain PUFA (LC-PUFA) with carbon chains that range from C18 to C24 are fairly well understood, especially in the retina and other neural tissues. A detailed account on the role and function of LC-PUFA in the retina was reviewed earlier (33)(34)(35)(36).Recent interest in the molecular and physiological roles of VLC-PUFA in the retina came from the fi nding that the gene associated with STGD3 shared sequence homologies with genes involved in FA elongation ( 37,38 ) Abbreviations: AOX, acyl-CoA oxidase; DHA or 22:6n3, docosahexaenoic acid; ELOVL, elongation of very long-chain FA; ELOVL4, elongation of very long-chain FA-4; ERG, electroretinogram; LC-PUFA, long-chain PUFA; PC, phosphatidylcholine; ROS, retinal outer segments; RPE, retinal pigment epithelium; STGD1, recessive Stargardt degeneration; STGD3, autosomal dominant Stargardt-like macular dystrophy; VLC-FA, very long-chain saturated or monounsaturated FA; VLC-PUFA, very long-chain PUFA.

Age-related macular degeneration (AMD) is a complex disease that has potential involvement of inflammatory and oxidative stress-related pathways in its pathogenesis. In search of effective therapeutic agents, we tested curcumin, a naturally-occurring compound with known antiinflammatory and anti-oxidative properties, in rat model of light induced retinal degeneration (LIRD) and in retina derived cell lines. We hypothesized that any compound effective against LIRD, which involves significant oxidative stress and inflammation, would be a candidate for further characterization for its potential application in AMD.We observed significant retinal neuroprotection in rats fed diets supplemented with curcumin (0.2% in diet) for 2 weeks. The mechanism of retinal protection from LIRD by curcumin involves inhibition of NF-κB activation and down-regulation of cellular inflammatory genes. When tested on retinaderived cell lines (661W and ARPE-19), pre-treatment of curcumin protected these cells from H 2 O 2 -induced cell death by up-regulating cellular protective enzymes, such as HO-1, thioredoxin.Since, curcumin with its pleiotropic activities can modulate the expression and activation of many cellular regulatory proteins such as NF-κB, AKT, NRF2 and growth factors, which in turn inhibit cellular inflammatory responses and protect cells; we speculate that curcumin would be an effective nutraceutical compound for preventive and augmentative therapy of AMD.