Novel mechanism of the co-regulation of nuclear transport of SmgGDS and Rac1. J Biol Chem 2003 Apr 04;278(14):12495-506
Date
01/29/2003Pubmed ID
12551911DOI
10.1074/jbc.M211286200Scopus ID
2-s2.0-0038485593 (requires institutional sign-in at Scopus site) 83 CitationsAbstract
The armadillo protein SmgGDS promotes guanine nucleotide exchange by small GTPases containing a C-terminal polybasic region (PBR), such as Rac1 and RhoA. Because the PBR resembles a nuclear localization signal (NLS) sequence, we investigated the nuclear transport of SmgGDS with Rac1 or RhoA. We show that the Rac1 PBR has significant NLS activity when it is fused to green fluorescent protein (GFP) or in the context of full-length Rac1. In contrast, the RhoA PBR has very poor NLS activity when it is fused to GFP or in the context of full-length RhoA. The nuclear accumulation of both Rac1 and SmgGDS is enhanced by Rac1 activation and diminished by mutation of the Rac1 PBR. Conversely, SmgGDS nuclear accumulation is diminished by interactions with RhoA. An SmgGDS nuclear export signal sequence that we identified promotes SmgGDS nuclear export. These results suggest that SmgGDS. Rac1 complexes accumulate in the nucleus because the Rac1 PBR has NLS activity and because Rac1 supplies the appropriate GTP-dependent signal. In contrast, SmgGDS.RhoA complexes accumulate in the cytoplasm because the RhoA PBR does not have NLS activity. This model may be applicable to other armadillo proteins in addition to SmgGDS, because we demonstrate that activated Rac1 and RhoA also provide stimulatory and inhibitory signals, respectively, for the nuclear accumulation of p120 catenin. These results indicate that small GTPases with a PBR can regulate the nuclear transport of armadillo proteins.
Author List
Lanning CC, Ruiz-Velasco R, Williams CLAuthor
Carol L. Williams PhD Professor in the Pharmacology and Toxicology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Active Transport, Cell NucleusAnimals
CHO Cells
Cell Nucleus
Cricetinae
Cytoplasm
Guanine Nucleotide Exchange Factors
Mutagenesis
Nuclear Localization Signals
rac1 GTP-Binding Protein
rhoA GTP-Binding Protein