Cortactin-Src Kinase Signaling Pathway Is Involved in N-syndecan-dependent Neurite Outgrowth*
- Tarja Kinnunen‡§¶‖,
- Marko Kaksonenद,
- Juhani Saarinen**,
- Nisse Kalkkinen**,
- H. Benjamin Peng‡ and
- Heikki Rauvala‡§
- From the ‡Laboratory of Molecular Neurobiology, Institute of Biotechnology, §Department of Biosciences, Division of Biochemistry, **Protein Chemistry Laboratory, Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki, Finland and the ‡Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill, North Carolina 27599
Abstract
N-syndecan (syndecan-3) was previously isolated as a cell surface receptor for heparin-binding growth-associated molecule (HB-GAM) and suggested to mediate the neurite growth-promoting signal from cell matrix-bound HB-GAM to the cytoskeleton of neurites. However, it is unclear whether N-syndecan would possess independent signaling capacity in neurite growth or in related cell differentiation phenomena. In the present study, we have transfected N18 neuroblastoma cells with a rat N-syndecan cDNA and show that N-syndecan transfection clearly enhances HB-GAM-dependent neurite growth and that the transfected N-syndecan distributes to the growth cones and the filopodia of the neurites. The N-syndecan-dependent neurite outgrowth is inhibited by the tyrosine kinase inhibitors herbimycin A and PP1. Biochemical studies show that a kinase activity, together with its substrate(s), binds specifically to the cytosolic moiety of N-syndecan immobilized to an affinity column. Western blotting reveals both c-Src and Fyn in the active fractions. In addition, cortactin, tubulin, and a 30-kDa protein are identified in the kinase-active fractions that bind to the cytosolic moiety of N-syndecan. Ligation of N-syndecan in the transfected cells by HB-GAM increases phosphorylation of c-Src and cortactin. We suggest that N-syndecan binds a protein complex containing Src family tyrosine kinases and their substrates and that N-syndecan acts as a neurite outgrowth receptor via the Src kinase-cortactin pathway.
Footnotes
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↵* This study was supported by grant from the Academy of Finland (to H. R.) and from the Sigrid Jusélius Foundation (to H. R., and H. B. P.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ Contributed equally to this work.
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↵‖ To whom correspondence should be addressed. Tel.: 358-9-70859062; Fax: 358-9-70859068.
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↵1 The abbreviations used are: HB-GAM, heparin-binding growth-associated molecule; PAGE, polyacrylamide gel electrophoresis; RAGE, receptor for advanced glycation end products.
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↵2 H. Huttunen and H. Rauvala, unpublished results.
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↵3 T. Kinnunen and H. Rauvala, unpublished results.
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↵4 M. Kaksonen and H. Rauvala, unpublished results.
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- Received August 12, 1997.
- Revision received January 13, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
