Structural Insights into Modulation of Neurexin-Neuroligin Trans-synaptic Adhesion by MDGA1/Neuroligin-2 Complex

• Published in: Neuron (Cambridge, Mass.) Mass.), 2017-06, Vol.94 (6), p.1121-1131.e6
• Main Authors: Kim, Jung A, Kim, Doyoun, Won, Seoung Youn, Han, Kyung Ah, Park, Dongseok, Cho, Eunju, Yun, Nayoung, An, Hyun Joo, Um, Ji Won, Kim, Eunjoon, Lee, Jie-Oh, Ko, Jaewon, Kim, Ho Min
• Format: Article
• Language: English
• Subjects: Animals; Assaying; Autism; Cell Adhesion; Cell adhesion & migration; Cell Adhesion Molecules, Neuronal - metabolism; Cercopithecus aethiops; COS Cells; Crystal structure; Crystallography; Glycosylphosphatidylinositol; GPI-Linked Proteins - metabolism; HEK293 Cells; Humans; inhibitory synapse formation; Interfaces; L Cells (Cell Line); Mass Spectrometry; MDGA1; MDGA2; Membranes; Mice; Mucin; Nerve Tissue Proteins - metabolism; Neural Cell Adhesion Molecules - metabolism; Neural Inhibition; neurexin; Neurogenesis; neuroligin-2; Neuromodulation; Neurons; Protein Binding; Protein Structure, Quaternary; Proteins; Studies; Synapses; Synapses - metabolism; synaptic adhesion
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2017.05.034

Membrane-associated mucin domain-containing glycosylphosphatidylinositol anchor proteins (MDGAs) bind directly to neuroligin-1 (NL1) and neuroligin-2 (NL2), thereby respectively regulating excitatory and inhibitory synapse development. However, the mechanisms by which MDGAs modulate NL activity to specify development of the two synapse types remain unclear. Here, we determined the crystal structures of human NL2/MDGA1 Ig1-3 complex, revealing their stable 2:2 arrangement with three interaction interfaces. Cell-based assays using structure-guided, site-directed MDGA1 mutants showed that all three contact patches were required for the MDGA’s negative regulation of NL2-mediated synaptogenic activity. Furthermore, MDGA1 competed with neurexins for NL2 via its Ig1 domain. The binding affinities of both MDGA1 and MDGA2 for NL1 and NL2 were similar, consistent with the structural prediction of similar binding interfaces. However, MDGA1 selectively associated with NL2, but not NL1, in vivo. These findings collectively provide structural insights into the mechanism by which MDGAs negatively modulate synapse development governed by NLs/neurexins. •Crystal structure of neuroligin-2 (NL2) in complex with MDGA1 Ig1-Ig3 domains•MDGA1 Ig1-Ig2 domains interact with NL2 dimer with 2:2 stoichiometry•MDGA1 competes with Nrx1β for NL2 binding via their overlapping binding site on NL2•MDGA1 selectively forms complexes with NL2, but not NL1, in vivo Kim et al. investigated the crystal structure of 2:2 heterotetrameric neuroligin-2/MDGA1 complexes and the molecular mechanism underlying MDGA1-mediated inhibition of neuroligin-2 synaptogenic activity. MDGA1 specifically associates with neuroligin-2 in vivo, suggesting a mechanism that restricts interaction of MDGA1 with neuroligin-2.