IPO5 (importin 5) is a nuclear transport receptor that mediates the import of cargo proteins into the nucleus by recognizing nuclear localization signals (NLS) and facilitating translocation through nuclear pore complexes via a Ran-GTPase-dependent mechanism 1. Beyond canonical nuclear import functions, IPO5 has emerged as a significant player in cancer progression and other diseases. In colorectal cancer, IPO5 is upregulated and promotes tumor development by mediating nuclear translocation of RASAL2, thereby activating RAS signaling pathways 1. Similarly, in esophageal cancer, elevated IPO5 expression correlates with poor prognosis and promotes malignant progression through MMP7 activation 2. IPO5 also plays unexpected roles in chemotherapy response, where it cooperates with PPP2R2B to facilitate nuclear import of ISG15, which subsequently inhibits DNA repair and increases cisplatin sensitivity in bladder cancer 3. Additionally, sphingosine-like compounds can bind IPO5 and inhibit its function while simultaneously activating PP2A, reducing nuclear accumulation of cancer-promoting proteins 4. Beyond malignancy, IPO5 is involved in spermatogenesis, where its abnormal accumulation in sperm flagella following FBXO24 deletion leads to male infertility 5. Genetic studies suggest IPO5 variants may contribute to schizophrenia pathophysiology through altered expression and alternative splicing 6.