Transport receptors of the importin β family continuously shuttle between the nucleus and cytoplasm. We previously reported that the nuclear export of importin β involves energy-requiring step(s) in living cells. Here, we show that the in vitro nuclear export of importin β also requires energy input. Cytosol, depleted of ATP-binding proteins, did not support the sufficient nuclear export of importin β. Further purification revealed that the active component in the absorbed fraction was a 70-kD heat shock cognate protein (hsc70). The addition of recombinant hsc70, but not an ATPase-deficient hsc70 mutant, to the depleted cytosol restored the export activity. In living cells, depletion of hsc70 caused the significant nuclear accumulation of importin β. These effects of hsc70 were observed in the nuclear export of importin β, but also for other import receptors, transportin and importin α. These results suggest that hsc70 broadly modulates nucleocytoplasmic transport systems by regulating the nuclear export of receptor proteins.
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10 October 2005
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October 03 2005
The 70-kD heat shock cognate protein (hsc70) facilitates the nuclear export of the import receptors
Shingo Kose,
Shingo Kose
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
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Maiko Furuta,
Maiko Furuta
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
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Makiko Koike,
Makiko Koike
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
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Yoshihiro Yoneda,
Yoshihiro Yoneda
2Department of Frontier Biosciences, Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
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Naoko Imamoto
Naoko Imamoto
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
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Shingo Kose
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
Maiko Furuta
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
Makiko Koike
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
Yoshihiro Yoneda
2Department of Frontier Biosciences, Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
Naoko Imamoto
1Cellular Dynamics Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198, Japan
Correspondence to Naoko Imamoto: [email protected]
Abbreviations used in this paper: hsc70, 70-kD heat shock cognate protein; NPC, nuclear pore complex; NTF2, nuclear transport factor 2; RCC1, regulator of chromosomal condensation; siRNA, small interfering RNA; TB, transport buffer.
Received:
June 14 2005
Accepted:
September 06 2005
Online ISSN: 1540-8140
Print ISSN: 0021-9525
The Rockefeller University Press
2005
J Cell Biol (2005) 171 (1): 19–25.
Article history
Received:
June 14 2005
Accepted:
September 06 2005
Citation
Shingo Kose, Maiko Furuta, Makiko Koike, Yoshihiro Yoneda, Naoko Imamoto; The 70-kD heat shock cognate protein (hsc70) facilitates the nuclear export of the import receptors . J Cell Biol 10 October 2005; 171 (1): 19–25. doi: https://doi.org/10.1083/jcb.200506074
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