Table 1.

Selectivity of −S4 β-neurexins and +B neuroligin for glutamatergic synapses, and +S4 β-neurexins and −B neuroligins for GABAergic synapses

A. Effect of splicing on relative binding affinitiesa
B. Induction of postsynaptic protein clustering by +S4 neurexin 1β in co-culture assaysb
Proteins:	Neuroligin 1/3/4	Neuroligin 2	PSD-95	Gephyrin
Clustering (%):	65c	90c	50c, 7d	104c, 110d
C. Enhancement of selective presynaptic input onto neurons by overexpression of neuroligin variantse
	Neuroligin 1 +B	Neuroligin 1 −B		Neuroligin 2 (always −B)
Enhancement of VGlut1:	4.7d, 1.5f	2.5d		5.3d, 1.5f
Enhancement of VGAT:	1.5d, 2.2f	5.0d		5.6d, 3.0f

^aLine widths reflect affinity of interaction. β-Neurexins that contain an insert at site 4 (+S4) interact preferentially with neuroligins that lack an insert at the B site (−B); they have lower affinity for +B neuroligin. β-Neurexins that lack an insert at site 4 (−S4) interact with −B neuroligins and +B neuroligin with equal affinity [9••,43••,44••].

^bInduction is reported normalized to 100% induction by neurexin 1β (−S4).

^cFrom [9••].

^dFrom [44••].

^eEnhancement is reported as increased density of inputs immunoreactive for VGlut (a marker of glutamatergic presynapses) or VGAT (a marker of GABAergic presynapses) relative to a value of 1.0 for control input density onto neurons expressing enhanced green fluorescent protein (EGFP). The neuroligin forms tested all contained the A-site insert.

^fFrom [35].