title: Intracellular transport of fat-soluble vitamins A and E.
abstract: Vitamins are compounds that are essential for the normal growth, reproduction and functioning of the human body. Of the 13 known vitamins, vitamins A, D, E and K are lipophilic compounds and are therefore called fat-soluble vitamins. Because of their lipophilicity, fat-soluble vitamins are solubilized and transported by intracellular carrier proteins to exert their actions and to be metabolized properly. Vitamin A and its derivatives, collectively called retinoids, are solubilized by intracellular retinoid-binding proteins such as cellular retinol-binding protein (CRBP), cellular retinoic acid-binding protein (CRABP) and cellular retinal-binding protein (CRALBP). These proteins act as chaperones that regulate the metabolism, signaling and transport of retinoids. CRALBP-mediated intracellular retinoid transport is essential for vision in human. α-Tocopherol, the main form of vitamin E found in the body, is transported by α-tocopherol transfer protein (α-TTP) in hepatic cells. Defects of α-TTP cause vitamin E deficiency and neurological disorders in humans. Recently, it has been shown that the interaction of α-TTP with phosphoinositides plays a critical role in the intracellular transport of α-tocopherol and is associated with familial vitamin E deficiency. In this review, we summarize the mechanisms and biological significance of the intracellular transport of vitamins A and E.
authors.affiliation: Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, the University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Kono
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D010716:Phosphatidylinositols / Q000378:metabolism; D012176:Retinoids / Q000378:metabolism*; D054840:Retinol-Binding Proteins, Cellular / Q000378:metabolism*; D014815:Vitamins / Q000378:metabolism*
chemical_list: D010716:Phosphatidylinositols; D012176:Retinoids; D054840:Retinol-Binding Proteins, Cellular; D014815:Vitamins
keywords: CRABP; CRALBP; CRBP; lipid transfer protein; vitamin; α-TTP