Promotes neurite outgrowth in hippocampal neurons. Involved in the regulation and maintenance of excitatory synapses. Induces the clustering of excitatory postsynaptic proteins, including DLG4, DLGAP1, GRIA1 and GRIN1 (By similarity). Can form heteromeric complexes with LRFN2, LRFN3, LRFN4 and LRFN5 (By similarity). Forms homomeric complexes, but not across cell junctions (By similarity). Interacts with DLG1, DLG2, DLG3 and DLG4. Interacts with 2 AMPA receptor subunits GRIA1 and GRIA2 and NMDA receptor subunit GRIN1 (By similarity). Detected in excitatory, but not inhibitory, synaptic plasma membrane. The PDZ-binding motif is required for neurite outgrowth promotion and for DLG1-, DLG3- and DLG4-binding. Glycosylated. Belongs to the LRFN family.