Importin β is a key protein in the nuclear transport receptor family, specifically responsible for transporting proteins with nuclear localization signals from the cytoplasm to the nucleus. This family is composed of multiple members, each with unique substrate specificity. Importin β binds to the NLS region of proteins and traverses the nuclear pore complex through an energy-dependent mechanism. It plays roles in cell division and growth and participates in various signaling pathways, essential for maintaining cellular physiological states and regulating gene expression. The expression of Importin β genes is tissue-specific, and abnormalities in its function or gene mutations are associated with the occurrence of various diseases, such as certain cancers and genetic disorders.