Distinct PTPmu-associated signaling molecules differentially regulate neurite outgrowth on E-, N-, and R-cadherin

Classical cadherins play distinct roles in axon growth and guidance in the visual system, however, the signaling pathways they activate remain unclear. Growth cones on each cadherin substrate have a unique morphology suggesting that distinct signals are activated by neurite outgrowth on E-, N-, and R-cadherin. We previously demonstrated that receptor protein tyrosine phosphatase-mu (PTPmu) is required for E- and N-cadherin-dependent neurite outgrowth. In this manuscript, we demonstrate that PTPmu regulates R-cadherin-mediated neurite outgrowth. Furthermore, we evaluated whether known PTPmu-associated signaling proteins, Rac1, Cdc42, IQGAP1 and PKCδ, regulate neurite outgrowth mediated by these cadherins. While Rac1 activity is required for neurite outgrowth on all three cadherins Cdc42/IQGAP1 are required only for N- and R-cadherin-mediated neurite outgrowth. In addition, we determined that PKC activity is required for E- and R-cadherin-mediated, but not N-cadherin-mediated neurite outgrowth. In summary, distinct PTPµ-associated signaling proteins are required to promote neurite outgrowth on cadherins.