R-Ras contains a proline-rich site that binds to SH3 domains and is required for integrin activation by R-Ras

Bingcheng Wang, June X Zou, Barbro Ek-Rylander, Erkki Ruoslahti

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


R-Ras contains a proline-rich motif that resembles SH3 domain-binding sites but that has escaped notice previously. We show here that this site in R-Ras is capable of binding SH3 domains and that the SH3 domain binding may be important for R-Ras function. A fusion protein containing the SH3 domains of the adaptor protein Nck interacted strongly with the R-Ras proline-rich sequence and with the intact protein. The binding was independent of whether R-Ras was in its GDP or GTP form. The Nck binding, which was mediated by the second of the three SH3 domains of Nck, was obliterated by mutations in the proline-rich sequence of R-Ras. The interaction of Nck with R-Ras could also be shown in yeast two-hybrid assays and by co-immunoprecipitation in human cells transfected with Nck and R-Ras. Previous results have shown that the expression of a constitutively active R-Ras mutant, R-Ras(38V), converts mouse 32D monocytic cells into highly adherent cells. Introducing the proline mutations into R-Ras(38V) suppressed the effect of R-Ras on 32D cell adhesion while not affecting GTP binding. These results reveal an unexpected regulatory pathway that controls R-Ras through an SH3 domain interaction. This pathway appears to be important for the ability of R-Ras to control cell adhesion.

Original languageEnglish (US)
Pages (from-to)5222-5227
Number of pages6
JournalJournal of Biological Chemistry
Issue number7
StatePublished - Feb 18 2000

ASJC Scopus subject areas

  • Biochemistry


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