PTPσ Is a Receptor for Chondroitin Sulfate Proteoglycan, an Inhibitor of Neural Regeneration

Chondroitin sulfate proteoglycans (CSPGs) present a barrier to axon regeneration. However, no specific receptor for the inhibitory effect of CSPGs has been identified. We showed that a transmembrane protein tyrosine phosphatase, PTP sigma, binds with high affinity to neural CSPGs. Binding involves the chondroitin sulfate chains and a specific site on the first immunoglobulin-like domain of PTP sigma. In culture, PTP sigma(-/-) neurons show reduced inhibition by CSPG. A PTP sigma fusion protein probe can detect cognate ligands that are up-regulated specifically at neural lesion sites. After spinal cord injury, PTP sigma gene disruption enhanced the ability of axons to penetrate regions containing CSPG. These results indicate that PTP sigma can act as a receptor for CSPGs and may provide new therapeutic approaches to neural regeneration.