VLC-PUFAs in Vision
In the retina, very-long-chain polyunsaturated fatty acids (VLC-PUFAs, which contain acyl chains longer than 26 carbons) are produced in photoreceptors through the elongation of LC-PUFAs mediated by Elongation of very-long-chain fatty acids like-4 (ELOVL4) and are highly enriched in the light-sensitive membrane disks of the photoreceptor outer segments. VLC-PUFAs were hypothesized to provide flexibility in the disk membrane interior by folding back on themselves on one side of the bilayer. The reduced levels of VLC-PUFAs may impair rhodopsin function, resulting in reduced visual function and photoreceptor degeneration. A recent report from our groups has further distinguished the major membrane domains of the rod OS disks, showing that compared to the rim regions of the disks, the center lamellar contained the vast majority of the LC- and VLC-PUFA (including DHA). This finding supports the idea that VLC-PUFAs exert the majority of their influence through interacting with rhodopsin, which is well aligned with a series of studies that showed increased rhodopsin activity in artificial liposomes enriched with DHA-containing phospholipids.
