NLGN1

NLGN1 is a postsynaptic cell adhesion molecule that organizes excitatory synapse assembly and plasticity by linking presynaptic and postsynaptic compartments (PMID:22723984, PMID:20010541). Its postsynaptic function is conserved and physiologically required: human NLGN1 rescues synaptic behavioral deficits in C. elegans nlg-1 mutants, and autism-associated mutations (R453C, D432X) abolish this rescue, defining residues critical for function (PMID:22723984, PMID:20010541). PKA phosphorylates NLGN1 at S839 near its PDZ ligand, and this modification dynamically tunes binding to the scaffold PSD-95; disrupting the NLGN1/PSD-95 interaction reduces NLGN1 surface expression and diminishes NLGN1-mediated synaptic enhancement, coupling phosphorylation state to synaptic trafficking (PMID:31138690). NLGN1 abundance is also set translationally downstream of mTORC1: elevated cap-dependent translation in Tsc2 heterozygous mice raises NLGN1, and lowering NLGN1 rescues mGluR-LTD and behavioral deficits, placing it as an effector limb of mTORC1 signaling (PMID:37293130).

1. 2009 Medium

   Established that neuroligin-1 is required for synaptic function at the organismal level, moving it from a candidate adhesion molecule to a functionally necessary synaptic component.

   Evidence Loss-of-function and RNAi behavioral assays (osmotic avoidance) in C. elegans nlg-1 mutants

   PMID:20010541

   Open questions at the time

   • No molecular partners or postsynaptic mechanism resolved
   • Phenotype is behavioral, not synapse-resolved
2. 2012 Medium

   Demonstrated that human NLGN1 acts postsynaptically and that specific disease-associated residues are functionally essential, by showing cross-species rescue and its loss with point/truncation mutations.

   Evidence Transgenic rescue and RNAi in C. elegans, site-directed mutagenesis, behavioral assays

   PMID:22723984

   Open questions at the time

   • Mechanism by which R453C/D432X abolish function not defined
   • Mammalian validation of rescue not addressed
3. 2019 High

   Identified a phosphoregulatory switch—PKA phosphorylation at S839—that controls NLGN1/PSD-95 binding and thereby surface trafficking and synaptic strength, explaining how NLGN1 function is dynamically gated.

   Evidence Phosphomimetic mutagenesis, Co-IP, surface expression and synaptic function assays in cultured neurons

   PMID:31138690

   Open questions at the time

   • Kinase/phosphatase regulation in vivo not established
   • Whether phosphorylation responds to defined activity signals unknown
4. 2023 Medium

   Placed NLGN1 downstream of mTORC1 by showing that translational upregulation of NLGN1 drives disease-relevant synaptic and behavioral deficits that are rescued by lowering NLGN1.

   Evidence Genetic knockdown and pharmacological inhibition of Nlgn1 in Tsc2 mice, mGluR-LTD electrophysiology, behavioral assays

   PMID:37293130

   Open questions at the time

   • Direct link between NLGN1 levels and LTD machinery not defined
   • Single model system
5. 2025 Low

   Implicated the NRXN3-NLGN1 transsynaptic complex and the MDGA2-NLGN1 interaction as additional regulators of glutamatergic synapse structure and stress-related plasticity.

   Evidence Maternal separation rat model with expression and dendritic morphology analysis (NRXN3); mammalian expression systems and hippocampal neurons with MDGA2 variant interaction assays (preprint)

   PMID:40286836

   Open questions at the time

   • NRXN3-NLGN1 finding is correlative without direct binding/mutagenesis
   • MDGA2 interaction reported in a preprint as a secondary finding without detailed methods

• How phosphoregulation, transsynaptic neurexin binding, MDGA2 competition, and mTORC1-driven abundance are integrated to set excitatory synapse number and strength in vivo remains unresolved.
• No unified in vivo model connecting trafficking control to translational control
• Structural basis of partner selectivity not addressed in this corpus