Presynaptic protein involved in both dopaminergic synaptic transmission and GABAergic system, thereby participating in the structural maturation of inhibitory interneuron synapses. Involved in the dopaminergic synaptic transmission by attenuating dopamine release through a presynaptic mechanism. Also participates in the GABAergic system. Interacts with TIAM1. Specifically present within the presynaptic compartment of synapses. Specifically present in developing cortical interneurons: highly expressed in cortical parvalbumin (PV) cells and midbrain dopaminergic neurons and is localized presynaptically (at protein level). Also present in the substantia nigra pars compacta (SnC) and ventral tegmental area (VTA) midbrain dopaminergic projection populations. Synaptic defects characterized by increased dopamine but decreased GABA signaling. A reduction in the output of cortical parvalbumin (PV)-positive GABAergic basket cells is observed, together with an increase of midbrain dopaminergic release in the nucleus accumbens. Increased dopaminergic signaling induces behavior abnormalities, characterized by severe and highly penetrant over-grooming behavior, resulting in whisker, face and sometimes body hair loss but rarely lesions. The over-grooming phenotype can be pharmacologically reversed following administration of haloperidol drug. Belongs to the neurexin family.