![]() To be activated RARs can bind to ATRA or 9-cis-RA while RXRs bind only to 9-cis-RA (Allenby G et al., 1993). ![]() RARA (RARα) is involved essentially in hematopoiesis, while RARγ (RARG) is assigned to the skin. There are two families of RA receptors, the RARs (retinoic acid receptor α, β, and γ: RARA, RARB, RARG) and the RXRs (retinoid X receptor α, β and γ: RXRA, RXRB, RXRG). ![]() All these isoforms are members of the retinoids, acting in different tissues after linkage with specific nuclear protein receptors. ATRA gives rise to 9-cis-RA, 11-cis-RA and 13-cis-RA, via an isomerase. Then retinal is oxidized as ATRA by a retinal dehydrogenase ( ALDH1A2 or RALDH). In target cells retinol is oxidized as retinal with the help of an alcohol dehydrogenase. The active retinol product is the retinoic acid (RA) which plays a great role as modulator of proliferation and differentiation in numerous tissues. Retinol (vitamin A) is strictly furnished by the nutrition. ![]() The gene response to RARA binding is modulated by a series of co-repressors and co-activators. Ligand-dependent transcription factor activated by all-trans retinoic acid (ATRA), specifically involved in hematopoietic stem cells differentiation and maturation = receptor for all-trans retinoic acid (ATRA) and 9-cis RA which are intracellular metabolites of vitamine A, active in cellular differentiation and morphogenesis.
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