Importin beta: conducting a much larger cellular symphony.
Importin beta, once thought to be exclusively a nuclear transport receptor, is emerging as a global regulator of diverse cellular functions. Importin beta acts positively in multiple interphase roles: in nuclear import, as a chaperone for highly charged nuclear proteins, and as a potential motor adaptor for movement along microtubules. In contrast, importin beta plays a negative regulatory role in mitotic spindle assembly, centrosome dynamics, nuclear membrane formation, and nuclear pore assembly. In most of these, importin beta is counteracted by its regulator, Ran-GTP. In light of this, the recent discovery of Ran's involvement in spindle checkpoint control suggested a potential new arena for importin beta action, although it is also possible that one of importin beta's relatives, the karyopherin family of proteins, manages this checkpoint. Lastly, importin beta plays a role in transducing damage signals from the axons of injured neurons back to the cell body.
Harel
Amnon
A
Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California, San Diego, 9500 Gilman Drive, Room 2124A, Pacific Hall, La Jolla, CA 92093, USA.
Forbes
Douglass J
DJ
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008870:Microtubules / Q000378:metabolism; D021381:Protein Transport; D008941:Spindle Apparatus / Q000378:metabolism; D028961:beta Karyopherins / Q000502:physiology*; D020931:ran GTP-Binding Protein / Q000378:metabolism
D028961:beta Karyopherins; D006160:Guanosine Triphosphate; D020931:ran GTP-Binding Protein