LRRC4 (Leu-rich repeat/LRR-containing glycoprotein 4), LRRC4B and LRRC4C are post-synaptic adhesion molecules of the LRR protein family that induce excitatory synapse formation. LRRC4 is also known as Brain tumor-associated protein BAG, Netrin-G2 ligand (NGL-2), Nasopharyngeal carcinoma-associated gene 14 protein (NAG14), which contains 1 Ig-like (immunoglobulin-like) domain and 9 LRR (leucine-rich) repeats, 1 LRRCT domain, 1 LRRNT domain. LRRC4 / NGL-2 specifically expressed in brain. LRRC4 / NGL-2 regulates the formation of exitatory synapses through the recruitment of pre-and-postsynaptic proteins. LRRC4 / NGL-2 organize the lamina/pathway-specific differentiation of dendrites. LRRC4 / NGL-2 plays a important role for auditory synaptic responses and involved in the suppression of glioma.