title: The unique N-terminus of R-ras is required for Rac activation and precise regulation of cell migration.
abstract: The Ras family GTPase, R-Ras, elicits important integrin-dependent cellular behaviors such as adhesion, spreading and migration. While oncogenic Ras GTPases and R-Ras share extensive sequence homology, R-Ras induces a distinct set of cellular behaviors. To explore the structural basis for these differences, we asked whether the unique N-terminal 26 amino acid extension of R-Ras was responsible for R-Ras-specific signaling events. Using a 32D mouse myeloid cell line, we show that full-length R-Ras activates Rac and induces Rac-dependent cell spreading. In contrast, truncated R-Ras lacking its first 26 amino acids fails to activate Rac, resulting in reduced cell spreading. Truncated R-Ras also stimulates more beta3 integrin-dependent cell migration than full-length R-Ras, suggesting that the N-terminus may negatively regulate cell movement. However, neither the subcellular localization of R-Ras nor its effects on cell adhesion are affected by the presence or absence of the N-terminus. These results indicate that the N-terminus of R-Ras positively regulates specific R-Ras functions such as Rac activation and cell spreading but negatively regulates R-Ras-mediated cell migration.
authors.affiliation: Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Holly
authors.forename: Mark K
authors.initials: MK
authors.lastname: Larson
authors.forename: Leslie V
authors.initials: LV
authors.lastname: Parise
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D004247:DNA / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D017384:Sequence Deletion; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D020558:GTP Phosphohydrolases; C513254:Rras protein, mouse; D020744:rac GTP-Binding Proteins; D018631:ras Proteins; D020741:rho GTP-Binding Proteins