Structural insights into the contactin 1 - neurofascin 155 adhesion complex.

Area of Science:

• Neuroscience
• Structural Biology
• Cell Biology

Background:

• Contactin 1 and neurofascin 155 are cell-surface proteins essential for nervous system development.
• They mediate cell adhesion to form and maintain paranodal myelin-axon junctions.
• The precise molecular mechanisms underlying their adhesion complex formation remain unclear.

Purpose of the Study:

• To elucidate the molecular mechanism of contactin 1-neurofascin 155 adhesion complex formation.
• To understand how structural variations contribute to diverse adhesion site formation.
• To determine the structural basis for paranodal spacing and intercellular bridging.

Main Methods:

• X-ray crystallography to determine structures of individual and complexed proteins.
• Biophysical analyses to characterize binding interactions.
• Cell-clustering assays to assess adhesion properties.

Main Results:

• Detailed structures of contactin 1 and neurofascin 155 binding regions were obtained.
• Conserved Ig1-2 interfaces mediate competing heterophilic (contactin 1-neurofascin 155) and homophilic (neurofascin 155-neurofascin 155) interactions.
• Contactin 1 forms low-affinity clusters via Ig3-6 interfaces.
• The Ig1-4 interaction defines the 7.4 nm paranodal spacing, with other domains bridging variable distances.

Conclusions:

• Structural plasticity, glycosylation, and splice variants enable diverse adhesion site formation.
• The elucidated structures provide a mechanistic understanding of paranodal junction formation and maintenance.
• This work clarifies how contactin 1 and neurofascin 155 control nervous system wiring through precise cell adhesion.