AhR (Aryl hydrocarbon receptor) is a ligand-activated transcription factor belonging to the bHLH-PAS family. It consists of multiple domains, including a DNA-binding domain and a ligand-binding domain, and is primarily located in the cytoplasm and nucleus. AhR functions in sensing environmental toxins, metabolic regulation, and immune responses. Upon activation by binding to aromatic hydrocarbon compounds, it translocates to the nucleus and influences the expression of target genes. The expression of AhR is tissue-specific, and mutations or dysregulation in its gene are associated with various diseases, including cancer, autoimmune diseases, and developmental abnormalities. The regulation of the AhR signaling pathway affects cell responses and adaptation to environmental changes.