IPO8
Description
The IPO8 (importin 8) is a protein-coding gene located on chromosome 12.
IPO8 is a gene that encodes Importin 8, a protein involved in the transport of proteins into the nucleus. It acts as a member of a group of proteins that interact with Ran, a GTPase that regulates nuclear transport. IPO8 binds to the nuclear pore complex and inhibits the activity of a protein that promotes the breakdown of Ran. Different isoforms of IPO8 are produced due to alternative splicing.
IPO8 is involved in the nuclear import of proteins, acting as either an autonomous nuclear transport receptor or as an adapter protein in association with the importin-beta subunit KPNB1. As an autonomous receptor, IPO8 binds nuclear localization signals (NLS) and promotes translocation of substrates through the nuclear pore complex (NPC) via a Ran-dependent, energy-requiring mechanism. At the nucleoplasmic side of the NPC, Ran binds to IPO8, causing the importin/substrate complex to dissociate and allowing IPO8 to be re-exported back to the cytoplasm where GTP hydrolysis releases Ran. The directionality of nuclear import is mediated by the uneven distribution of GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus. In vitro, IPO8 mediates the nuclear import of the signal recognition particle protein SRP19. IPO8 may also participate in the cytoplasm-to-nucleus shuttling of a diverse range of other cargos, including Argonaute-microRNA complexes, the JUN protein, RELA/NF-kappa-B p65 subunit, the translation initiation factor EIF4E, and a set of receptor-activated SMAD transcription factors involved in TGF-beta and BMP signaling.
IPO8 is also known as RANBP8, VISS.
