Acts as a synaptic organizer in specific subsets of neurons in the brain. Essential for long-term maintenance but not establishment of excitatory synapses. Functions as part of a trans-synaptic complex by binding to postsynaptic GRID1 and presynaptic neurexins. This interaction helps regulate the activity of NMDA and AMPA receptors at hippocampal synapses without affecting synapse formation. NRXN1B-CBLN2- GRID1 complex transduce presynaptic signals into postsynaptic NMDAR response. NRXN3B-CBLN2-GRID1 complex transduce presynaptic signals into postsynaptic AMPAR response. . This is the function of CBLN2 (cerebellin 2 precursor, Ensembl gene identifier ENSG00000141668).