q 2001 International Society for Neurochemistry, Journal of Neurochemistry, 78, 767±778 767 Journal of Neurochemistry, 2001, 78, 767±778 Soluble forms of NCAM and F3 neuronal cell adhesion molecules promote Schwann cell migration: identi®cation of protein tyrosine phosphatases z/b as the putative F3 receptors on Schwann cells Dimitra Thomaidou,* Delphine Coquillat,² , ³ Stathis Meintanis,* Masaharu Noda,§ Genevieve Rougon³ and Rebecca Matsas* *Laboratory of Cellular and Molecular Neurobiology, Department of Biochemistry, Hellenic Pasteur Institute, Athens, Greece ²Laboratoire de Genetique et Physiologie du Developpement, CNRS 6545 Parc Scienti®que de Luminy, Marseille, France ³Aventis Pasteur 1541 Avenue Marcel Me Ârieux, Marcy l'e Âtoile, France §Division of Molecular Neurobiology, National Institute for Basic Biology, Graduate University for Advanced Studies, Okazaki, Japan Abstract Neural cell adhesion molecule (NCAM) and F3 are both axonal adhesion molecules which display homophilic (NCAM) or heterophilic (NCAM, F3) binding activities and participate in bidirectional exchange of information between neurones and glial cells. Engineered Fc chimeric molecules are fusion proteins that contain the extracellular part of NCAM or F3 and the Fc region of human IgG1. Here, we investigated the effect of NCAM-Fc and F3-Fc chimeras on Schwann cell (SC) migration. Binding sites were identi®ed at the surface of cultured SCs by chimera coated ¯uorospheres. The functional effect of NCAM-Fc and F3-Fc binding was studied in two different SC migration models. In the ®rst, migration is monitored at speci®c time intervals inside a 1-mm gap produced in a monolayer culture of SCs. In the second, SCs from a dorsal root ganglion explant migrate on a sciatic nerve cryosection. In both systems addition of the chimeras signi®cantly increased the extent of SC migration and this effect could be prevented by the corresponding anti-NCAM or anti-F3 blocking antibodies. Furthermore, antiproteoglycan- type protein tyrosine phosphatase z/b (RPTPz/b) antibodies identi®ed the presence of RPTPz/b on SCs and prevented the enhancing effect of soluble F3 on SC motility by 95%. The F3-Fc coated Sepharose beads precipitated RPTPz/b from SC lysates. Altogether these data point to RPTPz/b is the putative F3 receptor on SCs. These results identify F3 and NCAM receptors on SC as potential mediators of signalling occurring between axons and glial cells during peripheral nerve development and regeneration. Keywords: chimeric molecules, development, migration, sciatic nerve, regeneration. J. Neurochem. (2001) 78, 767±778. The development and regeneration of peripheral nerves after injury involve the two major cellular components of the PNS, axons and Schwann cells (SC). It is now recognized that SC migration plays a fundamental role in normal development and the successful regeneration of peripheral nerves (Jessen and Mirsky 1999). During early develop- ment, SCs originating from the neural crest migrate along growing axons (Jessen et al. 1994) and studies using axonal and SC markers, suggest that migrating SCs participate in axonal guidance during development (Noakes and Bennett. 1987, Noakes et al. 1988). After this initial migration along the axonal surfaces, SCs migrate radially into the nerve bundles, proliferate actively and extend processes so that they gradually segregate axons into progressively smaller bundles. Shwann cell proliferation, migration and segrega- tion continue such that in the early neonate each myelinated Received January 26, 2001; revised manuscript received May 15, 2001; accepted May 18, 2001. Address correspondence and reprint requests to Dr Rebecca Matsas, Laboratory of Cellular and Molecular Neurobiology, Department of Biochemistry, Hellenic Pasteur Institute, 127 Vas So®as Avenue, 115 21 Athens, Greece. E-mail: rmatsa@mail.pasteur.gr Abbreviations used: Ara-C, cytosine arabinoside; CMFDA, 5-chloromethyl-¯uorescence diacetate; DM, de®ned medium; DMEM, Dulbecco's modi®ed Eagle's medium; DRG, dorsal root ganglion; FCS, fetal calf serum; NCAM, neural cell adhesion molecule; PBS, phosphate buffered saline; RPTPz/b, protein tyrosine phosphatase z/receptor-like protein tyrosine phosphatase b; SC, Schwann cells.