3BP-1, an SH3 domain binding protein, has GAP activity for Rac and inhibits growth factor-induced membrane ruffling in fibroblasts.
The SH3 binding protein, 3BP-1, was originally cloned as a partial cDNA from an expression library using the Abl SH3 domain as a probe. In addition to an SH3 binding domain, 3BP-1 displayed homology to a class of GTPase activating proteins (GAPs) active against Rac and Rho proteins. We report here a full length cDNA of 3BP-1 which extends the homology to GAP proteins previously noted. 3BP-1 functions in vitro as a GAP with a specificity for Rac-related G proteins. Microinjection of the 3BP-1 protein into serum-starved fibroblasts produces an inhibition of platelet-derived growth factor (PDGF)-induced membrane ruffling mediated by Rac. Co-injection of 3BP-1 with an activated Rac mutant that is unresponsive to GAPs, counter-acts this inhibition. 3BP-1 does not show in vitro activity towards Rho and, in agreement with this finding, microinjection of 3BP-1 into fibroblasts has no effect on lysophosphatidic acid (LPA)-induced stress fiber assembly mediated by Rho. Thus 3BP-1 is a new and specific Rac GAP that can act in cells to counter Rac-mediated membrane ruffling. How its SH3 binding site interacts with its GAP activity remains to be understood.
Cicchetti
P
P
Rockefeller University, New York, NY 10021, USA.
Ridley
A J
AJ
Zheng
Y
Y
Cerione
R A
RA
Baltimore
D
D
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D005786:Gene Expression Regulation; D016391:Genes, src; D006133:Growth Substances / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008246:Lysophospholipids / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D015513:Oncogene Proteins / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D051562:Proto-Oncogene Proteins c-bcr; D017386:Sequence Homology, Amino Acid; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins
D000199:Actins; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D006133:Growth Substances; D008246:Lysophospholipids; D015513:Oncogene Proteins; D010712:Phosphatidic Acids; D011518:Proto-Oncogene Proteins; C094762:Sh3bp1 protein, mouse; D006160:Guanosine Triphosphate; D011505:Protein-Tyrosine Kinases; C496614:Bcr protein, mouse; D051562:Proto-Oncogene Proteins c-bcr; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins