title: Activation of Rac1 by Rho-guanine nucleotide dissociation inhibitor-beta with defective isoprenyl-binding pocket.
abstract: Rho-guanine nucleotide dissociation inhibitor-beta (RhoGDIbeta), a regulator for Rho GTPases, is implicated in cancer cell progression. We reported that C-terminal truncated RhoGDIbeta (DeltaC(166-201)-RhoGDIbeta) promoted metastasis through activating Rac1 signaling pathway in ras-transformed fibroblast cells. To better understand the mechanism of Rac1 activation by DeltaC(166-201)-RhoGDIbeta during metastasis, the amount of GTP-bound Rac1 was measured as the activation level of Rac1 in cells expressing various mutant RhoGDIbeta with sequential C-terminal deletions. Three C-terminal hydrophobic amino acid residues (Trp191, Leu193, and Ile195) supposed to interact with isoprenyl groups of Rac1, was indispensable for a proper regulation of Rac1 activation/inhibition. Deletion of this region led RhoGDIbeta to continuously associate with GTP-bound Rac1, provoking constitutive activation of Rac1. Thus, impaired interaction of RhoGDIbeta with Rac1 isoprenyl groups possibly makes RhoGDIbeta function as a positive regulator for Rac1 during metastasis.
authors.affiliation: Division of Molecular Oncology and Virology, Medical Research Institute, Kanazawa Medical University, Daigaku, Uchinada, Ishikawa 920-0293, Japan. takahide@kanazawa-med.ac.jp
authors.forename: Takahide
authors.initials: T
authors.lastname: Ota
authors.forename: Masayo
authors.initials: M
authors.lastname: Maeda
authors.forename: Manabu
authors.initials: M
authors.lastname: Murakami
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Takegami
authors.forename: Shiho
authors.initials: S
authors.lastname: Suto
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tatsuka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D041702:BALB 3T3 Cells; D020730:Guanine Nucleotide Dissociation Inhibitors; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D011506:Proteins; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020830:rac1 GTP-Binding Protein