Rap1 promotes cell spreading by localizing Rac guanine nucleotide exchange factors.
The Ras-related GTPase Rap1 stimulates integrin-mediated adhesion and spreading in various mammalian cell types. Here, we demonstrate that Rap1 regulates cell spreading by localizing guanine nucleotide exchange factors (GEFs) that act via the Rho family GTPase Rac1. Rap1a activates Rac1 and requires Rac1 to enhance spreading, whereas Rac1 induces spreading independently of Rap1. Active Rap1a binds to a subset of Rac GEFs, including VAV2 and Tiam1 but not others such as SWAP-70 or COOL-1. Overexpressed VAV2 and Tiam1 specifically require Rap1 to promote spreading, even though Rac1 is activated independently of Rap1. Rap1 is necessary for the accumulation of VAV2 in membrane protrusions at the cell periphery. In addition, if VAV2 is artificially localized to the cell edge with the subcellular targeting domain of Rap1a, it increases cell spreading independently of Rap1. These results lead us to propose that Rap1 promotes cell spreading by localizing a subset of Rac GEFs to sites of active lamellipodia extension.
Fred Hutchison Cancer Research Center, Seattle, WA 98109, USA. barthur@fhcrc.org
William T
WT
Arthur
Lawrence A
LA
Quilliam
Jonathan A
JA
Cooper
D002448:Cell Adhesion; D018797:Cell Cycle Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D015778:Minor Histocompatibility Antigens; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D011554:Pseudopodia / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D014162:Transfection; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
C576606:ARHGEF7 protein, human; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D015778:Minor Histocompatibility Antigens; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011506:Proteins; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; C491873:SWAP70 protein, human; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; C093651:VAV2 protein, human; D005982:Glutathione Transferase; D020744:rac GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins