Characterization of the solution structure of a neuroligin/β-neurexin complex

Abstract

SUMMARYNeuroligins are postsynaptic cell adhesion molecules that promote synaptic maturation and stabilization upon binding with presynaptic partners, the α-and β-neurexins. Using a combination of analytical ultracentrifugation, small angle x-ray, and neutron scattering, we have characterized the low-resolution three-dimensional structure of the extracellular domain of the neuroligins, free in solution, and in complex with β-neurexin. The globular extracellular domain of the neuroligins forms stable homodimers through a four-helix bundle typical of the cholinesterases and other members of the α/β-hydrolase fold family. The presence of the stalk region adds to the extracellular domain of neuroligin-1 an elongated structure, suggesting a rod-like nature of the stalk domain. Sedimentation equilibrium coupled with solution scattering data of the β-neurexin/neuroligin-1 complex indicated a 2:2 stoichiometry where two β-neurexin molecules bind to a neuroligin-1 dimer. Deuteration of neurexin allowed us to collect neutron scattering data that, in combination with other biochemical techniques, provide a basis for optimizing the positioning of each component in a higher resolution computational model of the neuroligin/neurexin complex. As several mutations of both neurexin and neuroligin genes have been linked to autism spectrum disorders and mental retardation, these new structures provide an important framework for the study of altered structure and function of these synaptic proteins.

Cis and Trans Actions of the Cholinesterase-like Domain within the Thyroglobulin Dimer

“…The Tg ChEL domain, for instance, physically associates with I-II-III with an equimolar binding stoichiometry (Fig. 6); identical to that found for neuroligin-1 and its binding partner ␤-neurexin (40). In this report, we found that AChE and secretory neuroligins also can bind to upstream Tg regions I-II-III (Fig.…”

“…3, lower). These data directly implicate the carboxyl-terminal ␣-helices in ChEL dimerization, strongly supporting a 4-helix bundle dimerization mechanism similar to that used by AChE and other cholinesterase-like family members (39,40).…”

“…Bi-directional stabilization (ChEL stabilizing I-II-III, and I-II-III stabilizing ChEL) appears to be such a potential mechanism (25), which may be involved in extra-allelic suppression of Tg mutations (that would be otherwise incompetent for secretion in homozygotes or compound heterozygotes). Dimerization is also critical for neuroligin function and may be important for its secretion (40), while cross-dimerization with wild-type ChEL enhances NL3 secretion efficiency (Fig. 4D).…”

Dystroglycan Binding to α-Neurexin Competes with Neurexophilin-1 and Neuroligin in the Brain

“…Up to six alternative splice sites (SS#1–6) accept inserts ( red ). The stalk region between LNS6 and transmembrane region ( TM ) is visualized as rod-like due to massive O- glycosylation ( 119 ). B , binding of αDAG (immunoblots, upper panel ) and Nlgn1 ( middle panel ) from mouse brain was tested by pull-down with Fc-tagged extracellular domain of Nrxn1α carrying an insert in SS#4 ( lane 4 ).…”

Monozygotic twins discordant for submicroscopic chromosomal anomalies in 2p25.3 region detected by array CGH

“…SNTG2 encodes a scaffolding protein which interacts with neuroligins (NL4X and NL4Y) . Mutations of neuroligins (NL3 and NL4X) are implicated in autism and ID . Furthermore, Rosenfeld et al identified by whole‐genome arrays in a cohort of 1461 individuals referred for autism spectrum disorder a patient with a deletion involving a part of SNTG2 .…”