The aryl hydrocarbon receptor, known as AHR, is a normally cytosolic transcription factor that can bind to foreign compounds such as flavonoids and indoles from foods, as well as synthetic ligands including polychlorobiphenyls (PCBs) and polychlorinated dibenzo-p-dioxins (PCDD). This includes 2,3,7,8-tetrachlorodibenzodioxin (TCDD), which is the ligand shown in this pathway. AHR interacts with heat shock protein 90 (HSP90AA1), which acts as a chaperone for it. After this association, the ligand, in this case TCDD, can form a covalent bond with the complex in the cell's cytoplasm. This binding causes AHR and the rest of the complex to translocate into the nucleus of the cell. Once in the nucleus, the heat shock protein dissociates, leaving binding sites which the AHR nuclear translocator (ARNT) then binds to. Finally, the AHR/ARNT complex can interact, either directly or indirectly, with the DNA, in this case specifically a dioxin response element. With other ligands, the complex will bind to the equivalent DNA that corresponds to the genes that allow metabolism of the ligand.

Ahr Signal Transduction Pathway References