C-terminal sequences in R-Ras are involved in integrin regulation and in plasma membrane microdomain distribution

• DOI: 10.1016/j.bbrc.2003.10.074
• Publication Date: 2003-10-27T22:15:40Z
• Authors: Malene Hansen; Ian A Prior; Paul E Hughes; Beat Oertli; Fan-Li Chou; Berthe M Willumsen; John F Hancock; Mark H Ginsberg
• Keywords: Biochemistry & Molecular Biology; Integrins; Out Signal-transduction; 270104 Membrane Biology; Molecular Sequence Data; Biophysics; R-ras; Activation; CHO Cells; H-ras; Kidney; Transformation; GTP Phosphohydrolases; Structure-Activity Relationship; 03 medical and health sciences; C1; Cricetulus; Membrane Microdomains; Species Specificity; Cricetinae; Animals; Homeostasis; Amino Acid Sequence; Suppression; 0303 health sciences; Gene-product; Integrin Affinity Modulation; Adapter Protein; Chimera; Cell Membrane; 500; 730108 Cancer and related disorders; Cytoplasmic Domains; Protein Structure, Tertiary; Subcellular Localization; Map Kinase; Kinase Pak1; ras Proteins

The small GTPases R-Ras and H-Ras are highly homologous proteins with contrasting biological properties, for example, they differentially modulate integrin affinity: H-Ras suppresses integrin activation in fibroblasts whereas R-Ras can reverse this effect of H-Ras. To gain insight into the sequences directing this divergent phenotype, we investigated a panel of H-Ras/R-Ras chimeras and found that sequences in the R-Ras hypervariable C-terminal region including amino acids 175-203 are required for the R-Ras ability to increase integrin activation in CHO cells; however, the proline-rich site in this region, previously reported to bind the adaptor protein Nck, was not essential for this effect. In addition, we found that the GTPase TC21 behaved similarly to R-Ras. Because the C-termini of Ras proteins can control their subcellular localization, we compared the localization of H-Ras and R-Ras. In contrast to H-Ras, which migrates out of lipid rafts upon activation, we found that activated R-Ras remained localized to lipid rafts. However, functionally distinct H-Ras/R-Ras chimeras containing different C-terminal R-Ras segments localized to lipid rafts irrespective of their integrin phenotype.