Article ; Online: Retinal-phospholipid Schiff-base conjugates and their interaction with ABCA4, the ABC transporter associated with Stargardt disease.
The Journal of biological chemistry
2023 Volume 299, Issue 5, Page(s) 104614
Abstract: N-retinylidene-phosphatidylethanolamine (N-Ret-PE), the Schiff-base conjugate formed through the reversible reaction of retinal (Vitamin A-aldehyde) and phosphatidylethanolamine, plays a crucial role in the visual cycle and visual pigment ... ...
| Abstract | N-retinylidene-phosphatidylethanolamine (N-Ret-PE), the Schiff-base conjugate formed through the reversible reaction of retinal (Vitamin A-aldehyde) and phosphatidylethanolamine, plays a crucial role in the visual cycle and visual pigment photoregeneration. However, N-Ret-PE can react with another molecule of retinal to form toxic di-retinoids if not removed from photoreceptors through its transport across photoreceptor membranes by the ATP-binding-cassette transporter ABCA4. Loss-of-function mutations in ABCA4 are known to cause Stargardt disease (STGD1), an inherited retinal degenerative disease associated with the accumulation of fluorescent di-retinoids and severe loss in vision. A larger assessment of retinal-phospholipid Schiff-base conjugates in photoreceptors is needed, along with further investigation of ABCA4 residues important for N-Ret-PE binding. In this study we show that N-Ret-PE formation is dependent on pH and phospholipid content. When retinal is added to liposomes or photoreceptor membranes, 40 to 60% is converted to N-Ret-PE at physiological pH. Phosphatidylserine and taurine also react with retinal to form N-retinylidene-phosphatidylserine and N-retinylidene-taurine, respectively, but at significantly lower levels. N-retinylidene-phosphatidylserine is not a substrate for ABCA4 and reacts poorly with retinal to form di-retinoids. Additionally, amino acid residues within the binding pocket of ABCA4 that contribute to its interaction with N-Ret-PE were identified and characterized using site-directed mutagenesis together with functional and binding assays. Substitution of arginine residues and hydrophobic residues with alanine or residues implicated in STGD1 significantly reduced or eliminated substrate-activated ATPase activity and substrate binding. Collectively, this study provides important insight into conditions which affect retinal-phospholipid Schiff-base formation and mechanisms underlying the pathogenesis of STGD1. |
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| MeSH term(s) | Humans ; ATP-Binding Cassette Transporters/metabolism ; Phosphatidylserines ; Phospholipids ; Retinoids/metabolism ; Stargardt Disease/metabolism |
| Chemical Substances | ABCA4 protein, human ; ATP-Binding Cassette Transporters ; N-retinylidene-phosphatidylethanolamine ; Phosphatidylserines ; Phospholipids ; Retinoids |
| Language | English |
| Publishing date | 2023-03-16 |
| Publishing country | United States |
| Document type | Journal Article ; Research Support, Non-U.S. Gov't |
| ZDB-ID | 2997-x |
| ISSN | 1083-351X ; 0021-9258 |
| ISSN (online) | 1083-351X |
| ISSN | 0021-9258 |
| DOI | 10.1016/j.jbc.2023.104614 |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
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