Neurite outgrowth in brain neurons induced by heparin-binding growth-associated molecule (HB-GAM) depends on the specific interaction of HB-GAM with heparan sulfate at the cell surface.
Heparin-binding growth-associated molecule (HB-GAM) is a cell-surface- and extracellular matrix-associated protein that lines developing axons in vivo and promotes neurite outgrowth in vitro. Because N-syndecan (syndecan-3) was found to function as a receptor in HB-GAM-induced neurite outgrowth, we have now studied whether the heparan sulfate side chains of N-syndecan play a role in HB-GAM-neuron interactions. N-Syndecan from postnatal rat brain was found to inhibit HB-GAM-induced but not laminin-induced neurite outgrowth when added to the assay media. The inhibitory activity was abolished by treating N-syndecan with heparitinase, but it was retained in N-syndecan-derived free glycosaminoglycan chains, suggesting that N-syndecan heparan sulfate at the cell surface is involved in HB-GAM-induced neurite outgrowth. Binding to HB-GAM and inhibition of neurite outgrowth was observed with heparin-related polysaccharides only; galactosaminoglycans were inactive. Significant inhibition of neurite outgrowth was induced by heparin and by N-syndecan heparan sulfate but not by heparan sulfates from other sources. A minimum of 10 monosaccharide residues were required for HB-GAM-induced neurite outgrowth. Experiments with selectively desulfated heparins indicated that 2-O-sulfated iduronic acid units, in particular, are of importance to the interaction with HB-GAM, were implicated to a lesser extent. Structural analysis of N-syndecan from 6-day-old rat brain indicated that the heparan sulfate chains contain sequences of contiguous, N-sulfated disaccharide units with an unusually high proportion (82%) of 2-O-sulfated iduronic acid residues. We suggest that this property of N-syndecan heparan sulfate is essential for HB-GAM binding and induction of neurite outgrowth.
Kinnunen
T
T
Laboratory of Molecular Neurobiology, University of Helsinki, Finland.
Raulo
E
E
Nolo
R
R
Maccarana
M
M
Lindahl
U
U
Rauvala
H
H
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000196:embryology / Q000648:ultrastructure; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016501:Neurites / Q000648:ultrastructure*; D009844:Oligosaccharides / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D011509:Proteoglycans / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins; D053670:Syndecan-3
D002352:Carrier Proteins; D016207:Cytokines; D006497:Heparan Sulfate; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D009844:Oligosaccharides; D011134:Polysaccharides; D011509:Proteoglycans; D011994:Recombinant Proteins; D053670:Syndecan-3; C508303:Sdc3 protein, rat; C066845:pleiotrophin