期刊
MOLECULAR & CELLULAR PROTEOMICS
卷 12, 期 1, 页码 145-157出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/mcp.M112.019414
关键词
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资金
- RIKEN Special Project Funding for Basic Science in Cellular System Project Research
- Japan Society for the Promotion of Science (JSPS) through the Funding Program for Next Generation World-Leading Researchers (NEXT Program)
- Grants-in-Aid for Scientific Research [23570164, 10J08344] Funding Source: KAKEN
The human importin-beta family consists of 21 nucleocytoplasmic transport carrier proteins that carry proteins and RNAs across the nuclear envelope through nuclear pores in specific directions. These transport carriers are responsible for the nucleocytoplasmic transport of thousands of proteins, but the cargo allocation of each carrier, which is necessary information if one wishes to understand the physiological context of transport, is poorly characterized. To address this issue, we developed a high-throughput method to identify the cargoes of transport carriers by applying stable isotope labeling by amino acids in cell culture to construct an in vitro transport system. Our method can be outlined in three steps. (1) Cells are cultured in a medium containing a stable isotope. (2) The cell membranes of the labeled cells are permeabilized, and proteins extracted from unlabeled cells are transported into the nuclei of the permeabilized cells. In this step, the reaction system is first depleted of all importin-beta family carriers and then supplemented with a particular importin-beta family carrier of interest. (3) Proteins in the nuclei are extracted and analyzed quantitatively via LC-MS/MS. As an important test case, we used this method to identify cargo proteins of transportin, a representative member of the importin-beta family. As expected, the identified candidate cargo proteins included previously reported transportin cargoes as well as new potential cargoes, which we corroborated via in vitro binding assays. The identified cargoes are predominately RNA-interacting proteins, affirming that cargoes allotted to the same carrier share functional characteristics. Finally, we found that the transportin cargoes possessed at least two classes of signal sequences: the well characterized PY-nuclear localization signals specific for transportin, and Lys/Arg-rich segments capable of binding to both transportin and importin-beta. Thus, our method will be useful for linking a carrier to features shared among its cargoes and to specific nuclear localization signals. Molecular & Cellular Proteomics 12: 10.1074/mcp.M112.019414, 145-157, 2012.
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