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.
ONYX Pharmaceuticals, Richmond, CA 94806.
J F
JF
Hancock
A
A
Hall
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