In situ structure of a gap junction-stomatin complex

Area of Science:

• Cell Biology
• Structural Biology
• Biophysics

Background:

• Gap junctions (GJs) are vital intercellular channels for cell communication and organ function.
• Existing structural data primarily comes from purified GJs, lacking in situ context.
• In vivo, GJs exhibit complex heteromeric formations and protein associations.

Purpose of the Study:

• To determine the in situ structure and organization of gap junctions in Caenorhabditis elegans.
• To identify associated proteins and their potential roles in GJ function.

Main Methods:

• Cryo-electron tomography and subtomogram averaging were employed to analyze C. elegans GJs.
• AlphaFold3 modeling and molecular dynamics simulations were used to predict protein interactions.
• Expression of GFP-tagged proteins confirmed structural hypotheses.

Main Results:

• Hexagonal arrays of GJs with distinct wide and narrow conformations were observed in primary embryonal cells.
• A novel, cap-like cytosolic protein assembly was identified, enclosing the GJ channel pore.
• Evidence suggests the cap is formed by UNC-1 stomatin, interacting with UNC-9 innexins.

Conclusions:

• The study provides the first in situ structural insights into C. elegans gap junctions.
• The identified UNC-1/stomatin cap represents a potential regulatory mechanism for GJ assembly and function.
• This finding may have implications for understanding GJ regulation in other organisms.