IQGAP1, a calmodulin-binding protein with a rasGAP-related domain, is a potential effector for cdc42Hs.
Proteins that associate with the GTP-bound forms of the Ras superfamily of proteins are potential effector targets for these molecular switches. A 195 kDa protein was purified from cell lysates by affinity chromatography on immobilized cdc42Hs-GTP and a corresponding cDNA was isolated. Sequence analysis revealed localized identities to calponin, the ... WW domain, unconventional myosins and to the rasGAP-related domain (GRD) contained in IRA, NF-1, SAR1 and rasGAP. p195 was found to be identical to IQGAP1, a protein previously reported to bind ras. Purified recombinant p195/IQGAP1 bound to and inhibited the GTPase activity of cdc42Hs and rac whereas no interaction with ras was detected. The C-terminal half of IQGAP1 containing the GRD bound to cdc42 and rac in a GRD-dependent fashion, but a smaller fragment containing only the GRD did not. Cdc42 was also co-immunoprecipitated from cell lysates with antibody specific to p195/IQGAP1. Calmodulin also co-immunoprecipitated with p195/IQGAP1 and was found to associate with fragments containing the IQ domain. Expression of a cDNA fragment encoding the GRD inhibited the CDC24/CDC42 pathway in yeast, but no effect on ras was observed. In mammalian cells, both endogenous and ectopically expressed p195/IQGAP1 were localized to lamellipodia and ruffling cell membranes, where co-localization with actin was apparent. These results suggest that IQGAP1 is an effector target for cdc42Hs and may mediate the effects of this GTPase on cell morphology.
Mesh Terms:
Amino Acid Sequence, Animals, Base Sequence, Calmodulin, Calmodulin-Binding Proteins, Carrier Proteins, Cell Cycle Proteins, Cell Line, Cell Membrane, Chromatography, Affinity, Cloning, Molecular, DNA, Complementary, GTP Phosphohydrolases, GTP-Binding Proteins, Immunohistochemistry, Molecular Sequence Data, Protein Binding, Sequence Homology, Amino Acid, cdc42 GTP-Binding Protein, ras GTPase-Activating Proteins
Amino Acid Sequence, Animals, Base Sequence, Calmodulin, Calmodulin-Binding Proteins, Carrier Proteins, Cell Cycle Proteins, Cell Line, Cell Membrane, Chromatography, Affinity, Cloning, Molecular, DNA, Complementary, GTP Phosphohydrolases, GTP-Binding Proteins, Immunohistochemistry, Molecular Sequence Data, Protein Binding, Sequence Homology, Amino Acid, cdc42 GTP-Binding Protein, ras GTPase-Activating Proteins
EMBO J.
Date: Jun. 17, 1996
PubMed ID: 8670801
View in: Pubmed Google Scholar
Download Curated Data For This Publication
1885
Switch View:
- Interactions 3