Gene selection, alternative splicing, and post-translational processing regulate neuroligin selectivity for...

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Neuroligins (NLs) and beta-neurexins (NXs) are key synaptic proteins mediating cell adhesion and initiating presynaptic maturation.
• Both NLs and NXs possess alternatively spliced inserts in their extracellular domains, suggesting complex regulatory roles.

Purpose of the Study:

• To investigate the oligomeric states and binding stoichiometry of neuroligin and beta-neurexin extracellular domains.
• To characterize the binding affinities between neuroligins and beta-neurexin-1 (NX1beta) and elucidate the role of alternative splicing in modulating these interactions.

Main Methods:

• Analytical ultracentrifugation to determine oligomeric states and complex formation.
• Surface plasmon resonance and affinity chromatography to quantify binding affinities and analyze splice insert effects.

Main Results:

• Extracellular domains of neuroligins exist as dimers, while beta-neurexins are monomeric.
• Neuroligin and beta-neurexin form a 2:2 complex, with affinities varying over two orders of magnitude between different neuroligins and NX1beta.
• Splice insert B in NL1 is crucial for NL1/NX1beta binding, while splice insert 4 in NX affects association modulation.

Conclusions:

• A complex neuroligin recognition code, established by gene selection, mRNA splicing, and post-translational modifications, dictates specific neuroligin-neurexin interactions.
• This rank-ordered affinity code is conserved across mammalian species, highlighting its fundamental importance in synaptic organization and function.