title: Disruption of oligomerization induces nucleocytoplasmic shuttling of leukemia-associated rho Guanine-nucleotide exchange factor.
abstract: The rgsRhoGEFs comprise a subfamily of three guanine nucleotide exchange factors, which function in linking heterotrimeric G-proteins to the monomeric RhoGTPase. Here, we reveal the novel finding that oligomerization of leukemia-associated RhoGEF (LARG) functions to prevent nucleocytoplasmic shuttling and to retain LARG in the cytoplasm. We establish that oligomerization is mediated by a predicted coiled-coil sequence (amino acids 1507-1520) in the extreme C terminus of LARG and that substitution of isoleucines 1507/1510 with alanines disrupts homo-oligomerization and leads to nucleocytoplasmic shuttling via the CRM1 nuclear transport pathway. In addition, we demonstrate that induced dimerization of an otherwise nuclear monomeric LARG mutant promotes cytoplasmic localization. Furthermore, we establish that nuclear import of monomeric LARG is mediated by the nuclear localization sequence (29)PTDKKQK(35) in the extreme N terminus. We propose that nucleocytoplasmic shuttling provides a mechanism for spatially regulating the activity of LARG toward its cytoplasmic targets and potentially new nuclear targets.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 S. 10 Street, 839 BLSB, Philadelphia, PA 19107, USA.
authors.forename: Elda
authors.initials: E
authors.lastname: Grabocka
authors.forename: Philip B
authors.initials: PB
authors.lastname: Wedegaertner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism*; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism*; D017931:DNA Primers; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D019913:Nuclear Localization Signals; D011487:Protein Conformation; D021381:Protein Transport; D064067:Rho Guanine Nucleotide Exchange Factors
chemical_list: C577222:ARHGEF12 protein, human; D001704:Biopolymers; D017931:DNA Primers; D020662:Guanine Nucleotide Exchange Factors; D019913:Nuclear Localization Signals; D064067:Rho Guanine Nucleotide Exchange Factors