A novel role for RhoGDI as an inhibitor of GAP proteins.
RhoGDI inhibits guanine nucleotide dissociation from post-translationally processed Rho and Rac proteins but its biochemical role in vivo is unknown. We show here that N-terminal effector site mutations in the Rac protein do not compromise its interaction with RhoGDI and that, whilst geranylgeranylation and -AAX proteolysis of the C-terminal CAAX motif of Rac1 and RhoA are required for efficient interaction with RhoGDI, methylesterification of the C-terminal cysteine residue is not required. In vitro, RhoGDI can form stable complexes with Rho and Rac proteins in both the GTP and GDP bound states. Furthermore the Rac-GTP--RhoGDI complex is resistent to the action of recombinant RhoGAP and recombinant BCR. Thus GDI, by complexing with Rac-GTP and preventing GAP stimulated GTP hydrolysis, may allow transit of the activated form of the Rac protein between physically separated activator and effector proteins in the cell.
Hancock
J F
JF
ONYX Pharmaceuticals, Richmond, CA 94806.
Hall
A
A
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004277:DNA, Single-Stranded; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D020690:GTPase-Activating Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009154:Mutation; D015513:Oncogene Proteins / Q000378:metabolism; D017368:Protein Prenylation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051562:Proto-Oncogene Proteins c-bcr; D011994:Recombinant Proteins / Q000378:metabolism; D020744:rac GTP-Binding Proteins; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020742:rhoA GTP-Binding Protein
C569638:ARHGDIA protein, human; D004277:DNA, Single-Stranded; D020690:GTPase-Activating Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D015513:Oncogene Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D006153:Guanosine Diphosphate; D000246:Adenosine Diphosphate Ribose; D006160:Guanosine Triphosphate; D011505:Protein-Tyrosine Kinases; C496613:BCR protein, human; D051562:Proto-Oncogene Proteins c-bcr; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein