ARTICLES

Cell Research (2006)16: 759-770
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A new interaction between Abi-1 and βPIX involved in PDGF-activated actin cytoskeleton reorganisation

Fanny Campa, Nikolaus Machuy, Alexander Klein, Thomas Rude

¹Max Planck Institute for Infection Biology, Department of Molecular Biology, Campus Charit¨¦ Mitte, Charit¨¦platz 1, Berlin 10 117, Germany; ²Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA

Correspondence: Thomas Rudel Tel: +49-30-28460-415; Fax: +49-30-28460-401 E-mail: rudel@mpiib-berlin.mpg.de Received 24 Feb 2006; revised 30 Jul 2006; accepted 31 Jul 2006; published online 29 Aug 2006

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Members of the Rho family of GTPases are key regulators of the actin cytoskeleton. In particular, activated Rac1 stimulates membrane dorsal ruffle formation in response to platelet-derived growth factor (PDGF). Abl-interactor (Abi)- 1 and βPIX, a guanine nucleotide exchange factor for Rac1, localise at these Rac1-induced actin structures and play important roles in the induction of membrane dorsal ruffling in response to PDGF in fibroblasts. Here, we demonstrate a novel interaction between Abi-1 and βPIX using the yeast two-hybrid system, in vitro pull-down assays, and in vivo co-immunoprecipitation experiments. In vitro, the C-terminal fragment of βPIX interacted with Abi-1, while in vivo the N-terminal fragment of βPIX interacted with Abi-1. The biological function of this interaction was investigated in mouse fibroblasts in response to PDGF stimulation. Abi-1 and βPIX co-localised in the cytoplasm and to membrane dorsal ruffles after PDGF treatment. We show that the co-expression of Abi-1 and truncated forms of βPIX in mouse fibroblasts blocked PDGF-induced membrane dorsal ruffles. Together, these results show that the interaction between Abi-1 and βPIX is involved in the formation of growth factor-induced membrane dorsal ruffles.

Cell Research (2006) 16:759-770. doi: 10.1038/sj.cr.7310091; published online 29 Aug 2006

Keywords: βPIX, Abi-1, PDGF, membrane dorsal ruffling, cytoskeleton