title: Extensive cargo identification reveals distinct biological roles of the 12 importin pathways.
abstract: Vast numbers of proteins are transported into and out of the nuclei by approximately 20 species of importin-β family nucleocytoplasmic transport receptors. However, the significance of the multiple parallel transport pathways that the receptors constitute is poorly understood because only limited numbers of cargo proteins have been reported. Here, we identified cargo proteins specific to the 12 species of human import receptors with a high-throughput method that employs stable isotope labeling with amino acids in cell culture, an in vitro reconstituted transport system, and quantitative mass spectrometry. The identified cargoes illuminated the manner of cargo allocation to the receptors. The redundancies of the receptors vary widely depending on the cargo protein. Cargoes of the same receptor are functionally related to one another, and the predominant protein groups in the cargo cohorts differ among the receptors. Thus, the receptors are linked to distinct biological processes by the nature of their cargoes.
authors.affiliation: Cellular Dynamics Laboratory, RIKEN, Wako, Japan.
authors.forename: Makoto
authors.identifier: 0000-0003-0868-5334
authors.initials: M
authors.lastname: Kimura
authors.affiliation: Cellular Dynamics Laboratory, RIKEN, Wako, Japan.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Morinaka
authors.affiliation: Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan.|Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Imai
authors.affiliation: Cellular Dynamics Laboratory, RIKEN, Wako, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kose
authors.affiliation: Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan.|Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan.
authors.forename: Paul
authors.initials: P
authors.lastname: Horton
authors.affiliation: Cellular Dynamics Laboratory, RIKEN, Wako, Japan.
authors.forename: Naoko
authors.identifier: 0000-0002-2886-3022
authors.initials: N
authors.lastname: Imamoto
mesh_terms: D006801:Humans; D007553:Isotope Labeling; D028884:Karyopherins / Q000378:metabolism*; D013058:Mass Spectrometry; D013379:Substrate Specificity
chemical_list: D028884:Karyopherins
keywords: SILAC; biochemistry; cell biology; human; importin; nuclear protein; nuclear transport; transportin