Importin-5 (IPO5)

Importin-5 is a member of the importin beta (karyopherin) family of nuclear transport receptors encoded by the IPO5 gene. It facilitates the nuclear import of cargo proteins with a nuclear localization signal (NLS) by binding these cargo proteins in the cytoplasm, docking at the nuclear pore complex, and enabling their import into the nucleus in a process regulated by the small GTPase Ran and nucleoside triphosphates[1][2][3]. Importin-5 plays a critical role in shuttling ribosomal proteins, histones H3/H4 (especially monomeric H3), and various viral proteins between cytoplasm and nucleus[2][3][5]. In oncology, importin-5 is of interest due to its aberrant overexpression in certain cancers and its centrality to protein trafficking that supports cell growth and survival[3]. It also functions in viral infection, as several viruses (e.g., HIV, HPV, influenza) hijack this pathway for nuclear import of their proteins. No selective clinically approved drugs target IPO5 directly, and disrupting its activity carries significant safety risks due to its fundamental roles in normal cell function[3][5].

Other names

Ran-binding protein 5 (RanBP5)Importin beta-3 (KPNB3)Karyopherin subunit beta 3Karyopherin beta 3

Mediates nuclear import by binding proteins with nuclear localization signals (NLS); releases cargo upon RanGTP binding; proteins utilize IPO5 for entry into the nucleus, including viral proteins (e.g., HIV-1 Rev, HPV16 E5) and cellular proteins (e.g., ribosomal proteins, histones)[2][3][5].