Involved in synaptic inhibition in the brain. Selectively regulates inhibitory presynaptic differentiation through interacting with presynaptic NRXN2. Interacts (Ig-like 1 domain) with NRXN2 (via Laminin G-like 1 domain) in a trans-interaction manner. Ig-like 1 domain is indispensable for synaptogenic activity whereas Ig-like 2 domain is secondarily responsible for the activity.