Retinoid Binding Protein
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Introduction
Retinoids are a general term for various active metabolites of vitamin A in the body, mainly including retinol, retinal and retinoic acid (RA). Its physiological function is mainly mediated by retinoid binding protein. There are mainly five retinol-binding proteins: (1)plasma retinal binding protein (RBP); (2)cellular retinol binding protein (CRBP); (3)cellular retinoic acid-binding protein (CRABP); (4)cellular retinal binding protein (CRALBP); (5)interphotoreceptor retinoid binding protein (IRBP). RBP belongs to (lipocalin), CRBP, CRABP, etc. belong to intracellular lipid-binding protein (iLBP) superfamily. CRALBP and IRBP do not belong to the above two categories, the former is similar to vitamin E transporter and SEC14. IRBP has multiple ligand binding sites. The function of retinoid binding proteins is primarily to store and transport retinol in a liquid phase environment while protecting these hydrophobic ligands.
Mechanism of action
RBP is mainly responsible for the binding and transport of all-trans retinol in plasma. It can regulate the uptake of vitamin A by the membrane receptor Rpe65 or the downstream reaction state. Lecithin retinol acyltransferase (LRAT) is a substance that activates retinol, which regulates the storage, distribution and metabolism of vitamin A by binding to LRAT. CRABP can promote the activity of retinoic acid-metabolizing enzymes and reduce the level of retinoic acid in cells. When retinoic acid is combined with CRABP, it can promote the reactivity of microsomal enzymes to retinoic acid and produce a variety of products. (CRALBP) and (IRBP) act as eye-specific retinol-binding proteins that have a special role in the visual cycle. IRBP is important for the survival of photoreceptor cells.
Application of Retinoid binding proteins
The retinol-binding protein stores and transports retinol in a liquid phase environment, and its concentration in the body changes to reflect changes in Retinoids in the body. When glomerular dysfunction occurs, the concentration of serum Retinoid binding proteins increases, and the concentration of serum retinoid binding proteins decreases during hepatobiliary disease. It is a good indicator for evaluating kidney disease and hepatobiliary diseases. In addition, there is also good expression for retinopathy.
References
- Borst, D. E., Redmond, T. M., Elser, J. E., Gonda, M. A., Wiggert, B., Chader, G. J., & Nickerson, J. M. (1989). Interphotoreceptor retinoid-binding protein. Gene characterization, protein repeat structure, and its evolution. Journal of Biological Chemistry, 264(2), 1115-1123.
- John, E., & Yune, M. (1998). The complex between retinal and RBP is formed in the rough microsomes of liver following repletion of Vitamin A-depleted rats. Bio Biophysica Acta, 1380, 10-17.
