Fig 1. Molecular model of PTPσ signaling pathways in heterologous synapse formation.
A) PTPσ triggers excitatory heterologous synapse formation through a combination of extracellular and intracellular signaling components. The PTPσ D2 domain binds intracellular adaptor proteins (e.g., liprin-α) and substrates (e.g., p250RhoGAP and N-cadherin) to recruit the vesicular machinery for excitatory synapse development. This signal transduction model differs from that of neurexin.
B) Neurexins serve as anchor proteins that transduce postsynaptic signals from various ligands (e.g., neuroligins and leucine-rich repeat transmembrane proteins) and transfer them to adjacent, but as yet unidentified, coreceptor protein(s) to mediate the signal transduction cascades necessary for full heterologous synapse formation activity.