βPIX controls cell motility and neurite extension by regulating the distribution of GIT1

Lorena Za, Chiara Albertinazzi, Simona Paris, Mariacristina Gagliani, Carlo Tacchetti, Ivan de Curtis

Research output: Contribution to journalArticlepeer-review

Abstract

Cell motility entails the reorganization of the cytoskeleton and membrane trafficking for effective protrusion. GIT1/p95-APP1 is a member of a family of GTPase-activating proteins for ARF GTPases that affect endocytosis, adhesion and migration. GIT1 associates with paxillin and a complex including the Rac/Cdc42 exchanging factors PIX/Cool and the kinase PAK. In this study, we show that overexpression. of βPIX induces the accumulation of endogenous and over-expressed GIT1 at large structures similar to those induced by an ArfGAP-defective mutant of GIT1 (p95-C2). Immunohistochemical analysis and immunoelectron microscopy reveal that these structures include the endogenous transferrin receptor. Time-lapse analysis during motogenic stimuli shows that the formation and perinuclear accumulation of the p95-C2-positive structures is paralleled by inhibition of lamellipodium formation and cell retraction. Both dimerization and a functional SH3 domain of βPIX are required for the accumulation of GIT1 in fibroblasts, which is prevented by the monomeric PIX-PG-ALZ. This mutant also prevents the formation of endocytic aggregates and inhibition of neurite outgrowth in retinal neurons expressing p95-C2. Our results indicate that βPIX is an important regulator of the subcellular distribution of GIT1, and suggest that alteration in the level of expression of the complex affects the endocytic compartment and cell motility.

Original languageEnglish
Pages (from-to)2654-2666
Number of pages13
JournalJournal of Cell Science
Volume119
Issue number13
DOIs
Publication statusPublished - Jul 1 2006

Keywords

  • ArfGAP
  • GTPases
  • Membrane traffic
  • Motility
  • Neuritogenesis

ASJC Scopus subject areas

  • Cell Biology

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