Author's personal copy Research Article The PDZ protein MPP2 interacts with c-Src in epithelial cells Martin Baumgartner a, ⁎ ,1 , Andreas Weiss a,2,3 , Thorsten Fritzius a,3,4 , Jochen Heinrich a , Karin Moelling a,b a Institute of Medical Virology, University of Zürich, Zürich, Switzerland b Institute of Advanced Study, Berlin, Germany ARTICLE INFORMATION ABSTRACT Article Chronology: Received 7 August 2008 Revised version received 21 July 2009 Accepted 31 July 2009 Available online 6 August 2009 c-Src is a non-receptor tyrosine kinase involved in regulating cell proliferation, cell migration and cell invasion and is tightly controlled by reversible phosphorylation on regulatory sites and through protein–protein interactions. The interaction of c-Src with PDZ proteins was recently identified as novel mechanism to restrict c-Src function. The objective of this study was to identify and characterise PDZ proteins that interact with c-Src to control its activity. By PDZ domain array screen, we identified the interaction of c-Src with the PDZ protein Membrane Protein Palmitoylated 2 (MPP2), a member of the Membrane-Associated Guanylate Kinase (MAGUK) family, to which also the Discs large (Dlg) tumour suppressor protein belongs. The function of MPP2 has not been established and the functional significance of the MPP2 c-Src interaction is not known. We found that in non-transformed breast epithelial MCF-10A cells, endogenous MPP2 associated with the cytoskeleton in filamentous structures, which partially co-localised with microtubules and c-Src. MPP2 and c-Src interacted in cells, where c-Src kinase activity promoted increased interaction of c-Src with MPP2. We furthermore found that MPP2 was able to negatively regulate c-Src kinase activity in cells, suggesting that the functional significance of the MPP2-c-Src interaction is to restrict Src activity. Consequently, the c-Src-dependent disorganisation of the cortical actin cytoskeleton of epithelial cells expressing c-Src was suppressed by MPP2. In conclusion we demonstrate here that MPP2 interacts with c-Src in cells to control c-Src activity and morphological function. © 2009 Elsevier Inc. All rights reserved. Keywords: PDZ Dlg MAGUK Src Breast cancer cells Cytoskeleton Phosphorylation EXPERIMENTAL CELL RESEARCH 315 (2009) 2888 – 2898 ⁎ Corresponding author. Department of Clinical Research and Veterinary Public Health, Division of Molecular Pathobiology, University of Bern, Bern, Switzerland. Fax: +41 31 631 26 58. E-mail address: Martin.Baumgartner@mopa.unibe.ch (M. Baumgartner). Abbreviations: Dlg, Discs large; L27, Lin-2/Lin-7 domain; FERM, (four point 1, ezrin, radxin, moesin); IF, Immunofluorescence; MAGUK, Membrane- Associated Guanylate Kinase; MPP2, Membrane Protein Palmitoylated 2; PDZ, Postsynaptic density-95/Discs large 1/Zonula Occludens-1; SH, Src homology; Wb, Western blot 1 Current address: Department of Clinical Research and Veterinary Public Health, Division of Molecular Pathobiology, University of Bern, Bern, Switzerland. 2 Current address: Oncology Drug Discovery, Novartis Institutes for BioMedical Research, Basel, Switzerland. 3 These authors contributed equally. 4 Current address: Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland. 0014-4827/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.yexcr.2009.07.028 available at www.sciencedirect.com www.elsevier.com/locate/yexcr