The Nup358-RanGAP complex is required for efficient importin α/β-dependent nuclear import
In vertebrate cells, the nucleoporin Nup358/RanBP2 is a major component of the filaments that emanate from the nuclear pore complex into the cytoplasm. Nup358 forms a complex with SUMOylated RanGAP1, the GTPase activating protein for Ran. RanGAP1 plays a pivotal role in the establishment of a RanGTP...
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
May 01, 2008
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| In: |
Molecular biology of the cell
Year: 2008, Volume: 19, Issue: 5, Pages: 2300-2310 |
| ISSN: | 1939-4586 |
| DOI: | 10.1091/mbc.e07-12-1279 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1091/mbc.e07-12-1279 Verlag, lizenzpflichtig, Volltext: https://www.molbiolcell.org/doi/10.1091/mbc.e07-12-1279 
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| Author Notes: | Saskia Hutten, Annette Flotho, Frauke Melchior, and Ralph H. Kehlenbach |
| Summary: | In vertebrate cells, the nucleoporin Nup358/RanBP2 is a major component of the filaments that emanate from the nuclear pore complex into the cytoplasm. Nup358 forms a complex with SUMOylated RanGAP1, the GTPase activating protein for Ran. RanGAP1 plays a pivotal role in the establishment of a RanGTP gradient across the nuclear envelope and, hence, in the majority of nucleocytoplasmic transport pathways. Here, we investigate the roles of the Nup358-RanGAP1 complex and of soluble RanGAP1 in nuclear protein transport, combining in vivo and in vitro approaches. Depletion of Nup358 by RNA interference led to a clear reduction of importin α/β-dependent nuclear import of various reporter proteins. In vitro, transport could be partially restored by the addition of importin β, RanBP1, and/or RanGAP1 to the transport reaction. In intact Nup358-depleted cells, overexpression of importin β strongly stimulated nuclear import, demonstrating that the transport receptor is the most rate-limiting factor at reduced Nup358-concentrations. As an alternative approach, we used antibody-inhibition experiments. Antibodies against RanGAP1 inhibited the enzymatic activity of soluble and nuclear pore-associated RanGAP1, as well as nuclear import and export. Although export could be fully restored by soluble RanGAP, import was only partially rescued. Together, these data suggest a dual function of the Nup358-RanGAP1 complex as a coordinator of importin β recycling and reformation of novel import complexes. |
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| Item Description: | Online veröffentlicht: 27. Februar 2008 Gesehen am 05.09.2023 |
| Physical Description: | Online Resource |
| ISSN: | 1939-4586 |
| DOI: | 10.1091/mbc.e07-12-1279 |