Thematic Review Series: Fat-Soluble Vitamins: Vitamin A Vitamin A and retinoid signaling: genomic and nongenomic effects

Vitamin A or retinol is arguably the most multi- functional vitamin in the human body, as it is essential from embryogenesis to adulthood. The pleiotropic effects of vita- min A are exerted mainly by one active metabolite, all -trans retinoic acid (atRA), which regulates the expression of a bat- tery of target genes through several families of nuclear re- ceptors (RARs, RXRs, and PPAR / ), polymorphic retinoic acid (RA) response elements, and multiple coregulators. It also involves extranuclear and nontranscriptional effects, such as the activation of kinase cascades, which are inte- grated in the nucleus via the phosphorylation of several actors of RA signaling. However, vitamin A itself proved re- cently to be active and RARs to be present in the cytosol to regulate translation and cell plasticity. These new concepts expand the scope of the biologic functions of vitamin A and RA. —Al Tanoury, Z., A. Piskunov, and C. Rochette-Egly. Vitamin A and retinoid signaling: genomic and nongenomic effects. J. Lipid Res. 2013. 54: 1761-1775.