CIT-3 (CIT-N, citron-N or citron) is a splicing isoform of CIT that lacks the N-terminal kinase domain. CIT-3 is specifically expressed in the brain, where it participates in the formation of postsynaptic densities at glutamatergic synapses by binding to the postsynaptic density protein PSD-95 (DLG4). Binding of CIT-3 to DLG4 is RHO GTPase-dependent. DLG4 may simultaneously bind CIT-3 and NMDA-type glutamate receptors (Zhang et al. 1999, Furuyashiki et al. 1999, Zhang and Benson 2006).