FIGURE 1. Architecture of the trans-synaptic neurexin–neuroligin complex.

From the following article:

Neuroligins and neurexins link synaptic function to cognitive disease

Thomas C. Südhof

Nature 455, 903-911(16 October 2008)

doi:10.1038/nature07456

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a, The structure of an excitatory synapse and the putative locations of neurexins (NRXNs) and neuroligins (NLGNs) in the synapse. A presynaptic varicosity containing synaptic vesicles is shown on the left, and a postsynaptic spine with a postsynaptic density containing neurotransmitter receptors on the right. b, The NRXN–NLGN junction, including selected presynaptic and postsynaptic binding proteins: CASK, VELIs and MINTs on the presynaptic side62; and PSD95 (which binds to AMPA-type glutamate receptors through its first PDZ domain, and to NLGNs through its third PDZ domain64), GKAP and SHANKs on the postsynaptic side. Note that a proportion of NRXNs and CASK could be also postsynaptic, and that SHANKs might also be presynaptic. C, carboxyl terminus; CAMK, Ca2+/calmodulin-dependent protein kinase domain of CASK; CHO, carbohydrate-attachment sequence; E, epidermal growth factor (EGF)-like domain; GUK, guanylate-kinase domain; L, LNS (laminin, NRXN, sex-hormone-binding globulin) domain; N, amino terminus; P, PDZ domain; S, SH3 domain. c, Alternative splicing of NRXNs and NLGNs. alpha-NRXNs contain five canonical splice sites (1 to 5), and beta-NRXNs contain two (4 and 5). Splice site 1 is C-terminal to the first EGF-like domain. Splice sites 2, 3 and 4 are at similar positions in the second, fourth and sixth LNS domains, respectively. Splice site 5 is between the glycosylated CHO sequence and the transmembrane region. Most alternative splicing involves the insertions of small evolutionarily conserved sequences, except for at splice site 5. Splicing at this site in NRXN2 involves a large insertion (191 residues), and in NRXN3 it involves at least 16 variants, some of which include stop codons and thus produce secreted isoforms of NRXN3 (ref. 35). NLGNs contain only two sites of alternative splicing, and one of these sites, site B, is present only in NLGN1.

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