Functions as retinol transporter. Accepts all-trans retinol from the extracellular retinol-binding protein RBP4, facilitates retinol transport across the cell membrane, and then transfers retinol to the cytoplasmic retinol-binding protein RBP1 . Retinol uptake is enhanced by LRAT, an enzyme that converts retinol to all-trans retinyl esters, the storage forms of vitamin A . Contributes to the activation of a signaling cascade that depends on retinol transport and LRAT-dependent generation of retinol metabolites that then trigger activation of JAK2 and its target STAT5, and ultimately increase the expression of SOCS3 and inhibit cellular responses to insulin . Important for the homeostasis of vitamin A and its derivatives, such as retinoic acid . STRA6-mediated transport is particularly important in the eye, and under conditions of dietary vitamin A deficiency (Probable). Does not transport retinoic acid .
Cell membrane ; Multi-pass membrane protein . In the retinal pigment epithelium localizes to the basolateral membrane. .
Broad expression. In adult eye expressed in sclera, retina, retinal pigment epithelium, and trabecular meshwork but not in choroid and iris.
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