Synaptic adhesion protein. Regulates the formation of excitatory synapses. The trans-synaptic adhesion between LRRC4B and PTPRF regulates the formation of excitatory synapses in a bidirectional manner (By similarity). Interacts with PTPRF (By similarity). Interacts with DLG4. The extreme C-terminus binds to the first 2 PDZ domains of DLG4. N-glycosylated. O-glycosylated; contains sialic acid.