The FASEB Journal • Research Communication Integrin    3 is a pleiotrophin receptor required for pleiotrophin-induced endothelial cell migration through receptor protein tyrosine phosphatase / Constantinos Mikelis,* Evanthia Sfaelou,* Marina Koutsioumpa,* Nelly Kieffer, † and Evangelia Papadimitriou* ,1 *Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, Patras, Greece; and † Sino-French Research Center for Life Sciences and Genomics, CNRS/LIA124, Rui Jin Hospital, Jiao Tong University Medical School, Shanghai, China ABSTRACT We have previously shown that the angio- genic growth factor pleiotrophin (PTN) induces migra- tion of endothelial cells through binding to its receptor protein tyrosine phosphatase / (RPTP/ ). In this study, we show that a monoclonal antibody against    3 but not  5  1 integrin abolished PTN-induced human endothelial cell migration in a concentration-dependent manner. Integrin    3 was found to directly interact with PTN in an RGD-independent manner, whereas a synthetic peptide corresponding to the specificity loop of the  3 integrin extracellular domain ( 177 CYD- MKTTC 184 ) inhibited PTN-   3 interaction and totally abolished PTN-induced endothelial cell migration. In- terestingly,    3 was also found to directly interact with RPTP/, and PTN-induced Y773 phosphorylation of  3 integrin was dependent on both RPTP/ and the downstream c-src kinase activation. Midkine was found to interact with RPTP/, but not with    3 , and caused a small but statistically significant decrease in cell migration. In the same line, PTN decreased migra- tion of different glioma cell lines that express RPTP/ but do not express    3 , while it stimulated migration of U87MG cells that express    3 on their cell membrane. Overexpression or down-regulation of  3 stimulated or abolished, respectively, the effect of PTN on cell migration. Collectively, these data suggest that    3 is a key molecule that determines the stimu- latory or inhibitory effect of PTN on cell migration.— Mikelis, C., Sfaelou, E., Koutsioumpa, M., Kieffer, N., Papadimitriou, E. Integrin    3 is a pleiotrophin recep- tor required for pleiotrophin-induced endothelial cell migration through receptor protein tyrosine phospha- tase /. FASEB J. 23, 1459 –1469 (2009) Key Words: heparin affin regulatory peptide  heparin-binding growth associated molecule  angiogenesis  tumor growth  gli- oma Pleiotrophin (PTN), also known as heparin affin regulatory peptide or heparin binding growth-associ- ated molecule, is a secreted growth factor that together with midkine (MK) forms a family of structurally re- lated heparin binding growth factors that share many biological activities, the best characterized being neural development and tumor growth. Besides a direct effect of PTN on tumor cells, there is a plethora of reports indicating a positive correlation between PTN and in vivo or in vitro angiogenesis (1, 2). The receptors of PTN involved in its angiogenic effects are, however, still unidentified. We have shown that PTN induces human endothelial cell migration through its receptor protein tyrosine phosphatase / (RPTP/ ) (3). RPTP/ is predominantly expressed as a chondroitin sulfate proteoglycan (4), while it is also expressed in a nonproteoglycan form (5). Several different splice vari- ants of human RPTP/ have been described, including a transmembrane long form, a truncated transmembrane short form, and two secreted forms, termed 6B4 proteo- glycan/phosphacan and phosphacan short isoform (6). Several different ligands bind to the extracellular domain of RPTP/, including growth factors, extracellular ma- trix molecules, and cell adhesion molecules (6, 7). Inter- actions of RPTP/ with neuronal adhesion molecules have been implicated in glial–neuronal interaction and neuronal migration during development (8), while inter- actions with the Notch-related transmembrane protein Delta/Notch-like EGF-related receptor regulate neurito- genesis (9). Finally, RPTP/ was also found to colocalize with integrins  6  1 and  4  1 and this multimolecular complex mediated MK-induced osteoblastic cell migra- tion (10). Integrins are a family of transmembrane glycopro- teins that mediate cell– cell and cell–matrix interac- tions. All known members of this superfamily are noncovalently associated heterodimers composed of an  and a  subunit (11). The interaction between integrins and their ligands is important in a number of cellular processes, such as adhesion, migration, prolif- eration, differentiation, and survival (12). One of the most prevalent integrins,  v  3 , is expressed on almost all the cells originating from the mesenchyme and on a 1 Correspondence: Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, GR 26504 Greece. E-mail: epapad@upatras.gr doi: 10.1096/fj.08-117564 1459 0892-6638/09/0023-1459 © FASEB