In brain, Axl recruits Grb2 and the p85 regulatory subunit of PI3 kinase; in vitro mutagenesis defines the requisite binding sites for downstream Akt activation

Jason G. Weinger, Pouyan Gohari, Ying Yan, Jonathan M. Backer, Brian Varnum, Bridget Shafit-Zagardo

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

Axl is a receptor tyrosine kinase implicated in cell survival following growth factor withdrawal and other stressors. The binding of Axl's ligand, growth arrest-specific protein 6 (Gas6), results in Axl autophosphorylation, recruitment of signaling molecules, and activation of downstream survival pathways. Pull-down assays and immunoprecipitations using wildtype and mutant Axl transfected cells determined that Axl directly binds growth factor receptor-bound protein 2 (Grb2) at pYVN and the p85 subunit of phosphatidylinositol-3 kinase (PI3 kinase) at two pYXXM sites (pY779 and pY821). Also, p85 can indirectly bind to Axl via an interaction between p85's second proline-rich region and the N-terminal SH3 domain of Grb2. Further, Grb2 and p85 can compete for binding at the pY821VNM site. Gas6-stimulation of Axl-transfected COS7 cells recruited activated PI3 kinase and phosphorylated Akt. An interaction between Axl, p85 and Grb2 was confirmed in brain homogenates, enriched populations of O4+ oligodendrocytes, and O4- flow-through prepared from day 10 mouse brain, indicating that cells with active Gas6/Axl signal through Grb2 and the PI3 kinase/Akt pathways.

Original languageEnglish (US)
Pages (from-to)134-146
Number of pages13
JournalJournal of Neurochemistry
Volume106
Issue number1
DOIs
StatePublished - Jul 2008

Keywords

  • Akt signaling
  • Axl receptor tyrosine kinase
  • Growth arrest-specific protein 6
  • Growth factor receptor-bound protein 2
  • Oligodendrocytes
  • p85 subunit of phosphatidylinositol-3 kinase

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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