Neuroligins (NLGs) are postsynaptic adhesion molecules that bind presynaptic neurexins (NRXs) with nanomolar affinity (Südhof, 2008). Rodents have four NLG isoforms, each exhibiting a specific expression pattern and subcellular Autophagy inhibitor molecular weight distribution. In particular, NLG1 and NLG2 are localized to excitatory and inhibitory synapses, respectively (Graf et al., 2004). NLGs and NRXs contain intracellular domains that interact with scaffold proteins,

such as PSD95 and CASK (Südhof, 2008). Adhesion between NLGs and NRXs thus provides a structural bridge between pre- and postsynaptic scaffolding machinery. In humans, NRXs and NLGs have been strongly linked to autism spectrum disorders, emphasizing the importance of this transsynaptic complex for normal brain development (Südhof, 2008). Indeed, NLGs induce functional maturation of presynaptic terminals (Dean et al., 2003; Scheiffele et al., 2000; Wittenmayer et al., 2009), whereas NRXs cluster postsynaptic proteins (Graf et al.,

2004; Heine et al., 2008). Their Galunisertib ic50 ability to transaggregate synaptic components implicated NLGs and NRXs as critical mediators of synapse formation. This hypothesis was supported by in vitro studies showing that NLG levels correlate with the number of synapses generated during development (Chih et al., 2005; Dean et al., 2003; Graf et al., 2004; Levinson et al., 2005). However, NLG1-NLG3 triple knockout (KO) neurons exhibit normal synapse number and ultrastructural synaptic features, but present severe deficits in synaptic transmission (Varoqueaux et al., 2006),

indicating that, in vivo, NLGs are not required Oxymatrine for the initial stages of synaptogenesis, but are critical for proper synaptic function. Recent studies have further shown that NLGs regulate NMDA (Chubykin et al., 2007; Jung et al., 2010) and AMPA (Etherton et al., 2011; Heine et al., 2008; Shipman et al., 2011) receptor function and are involved in multiple forms of synaptic plasticity across species (Choi et al., 2011; Jung et al., 2010). Interestingly, overexpression of NLG1 in hippocampal slices and cultured neurons increases release probability through NRX-dependent mechanisms (Futai et al., 2007; Ko et al., 2009; Stan et al., 2010), whereas disruption of endogenous NLG-NRX interactions with soluble Fc-NRX fragments decreases miniature excitatory postsynaptic current (mEPSC) frequency and release probability (Levinson et al., 2005). In vivo, transgenic expression of NLG1 results in extended active zones and increased number of reserve pool vesicles (Dahlhaus et al., 2010), while neurons lacking αNRX1-αNRX3 exhibit deficits in synaptic transmission due to impaired N-type Ca2+ channel function (Missler et al., 2003). These results suggest that the NLG-NRX transsynaptic complex is an important regulator of presynaptic function. However, a limitation of most studies to date is the reliance on long-term manipulations susceptible to indirect compensatory mechanisms.