title: Differential properties of D4/LyGDI versus RhoGDI: phosphorylation and rho GTPase selectivity.
abstract: RhoA/B/C and CDC42/Rac, which form two subgroups of the rho guanosine triphosphatase (GTPase) family, regulate various aspects of actin cytoskeleton organisation. In cytosol, guanosine diphosphate (GDP) dissociation inhibitor (GDI) interacts with and maintains rho GTPases in their inactive GDP-bound form. RhoGDI is a ubiquitously expressed GDI, whereas D4/LyGDI is hematopoietic cell-specific and 10-fold less potent than RhoGDI in binding to and regulating rho GTPases. We have combined microanalytical liquid chromatography with the use of specific antibodies in order to separate D4/LyGDI and RhoDGI-complexes from the cytosol of U937 cells and to demonstrate that the two GDIs associate with different rho protein partners. RhoGDI can form a complex with CDC42Hs, RhoA, Rac1 and Rac2, while none of these GTPases was found to interact with D4/LyGDI. In addition, we found that stimulation of U937 cells with phorbol ester leads to phosphorylation of D4/LyGDI. Our results suggest that LyGDI forms complexes with specific rho GTPases expressed in hematopoietic cells where it may regulate specific pathways.
authors.affiliation: Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, France.
authors.forename: J P
authors.initials: JP
authors.lastname: Gorvel
authors.forename: T C
authors.initials: TC
authors.lastname: Chang
authors.forename: J
authors.initials: J
authors.lastname: Boretto
authors.forename: T
authors.initials: T
authors.lastname: Azuma
authors.forename: P
authors.initials: P
authors.lastname: Chavrier
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies; D000918:Antibody Specificity; D003600:Cytosol / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: C569638:ARHGDIA protein, human; C569658:ARHGDIB protein, human; D000906:Antibodies; D020690:GTPase-Activating Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D010446:Peptide Fragments; D011506:Proteins; D025521:Tumor Suppressor Proteins; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate