Identification of function-regulating antibodies targeting the receptor protein tyrosine phosphatase sigma ectodomain

Receptor tyrosine phosphatase sigma (RPTP sigma) plays an important role in the regulation of axonal outgrowth and neural regeneration. Recent studies have identified two RPTP sigma ligands, chondroitin sulfate proteoglycans (CSPGs) and heparan sulfate proteoglycans (HSPG), which can modulate RPTP sigma activity by affecting its dimerization status. Here, we developed a split luciferase assay to monitor RPTP sigma dimerization in living cells. Using this system, we demonstrate that heparin, an analog of heparan sulfate, induced the dimerization of RPTP sigma , whereas chondroitin sulfate increased RPTP sigma activity by inhibiting RPTP sigma dimerization. Also, we generated several novel RPTP sigma vertical bar gG monoclonal antibodies, to identify one that modulates its activity by inducing/stabilizing dimerization in living cells. Lastly, we demonstrate that this antibody promotes neurite outgrowth in SH-SY5Y cells. In summary, we demonstrated that the split luciferase RPTP sigma activity assay is a novel high throughput approach for discovering novel RPTP sigma modulators that can promote axonal outgrowth and neural regeneration.