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. Author manuscript; available in PMC: 2023 Feb 7.
Published in final edited form as: Oncol Res Treat. 2022 Feb 7;45(5):291–298. doi: 10.1159/000522425

Fig. 1. Simplified scheme for the retinoid signaling pathway.

Fig. 1.

Blood-circulating retinol is internalized through membrane transporter and receptor STRA6, not in all cell types, however it is converted into all-trans RA, which binds to CRABP2 for signaling in the nucleus. RA triggers gene transcription by binding to RARs and to retinoid X receptors (RXRs). In the presence of the ligand, RAR and RXR heterodimerize on RARE sequences located in promoter regions inducing the transcription of target genes. ADH, alcohol dehydrogenase; CRBP, cellular retinolbinding protein 1; Gαq, Gq protein alpha subunit; MAPK, mitogen-activated protein kinases; RALDH, retinaldehyde dehydrogenase; RBP4, retinol-binding protein 4; RDH, retinol dehydrogenase; STRA6, stimulated by RA 6; RARE, RA-response element.