Connexin channels and hemichannels are modulated differently by charge reversal at residues forming the intracellular...

Area of Science:

• Cell biology
• Biophysics
• Structural biology

Background:

• Connexins form channels for cell-to-cell communication.
• The β-subfamily of connexins possesses an intracellular pocket; its presence in other subfamilies was unknown.
• Connexin50 (Cx50) mutations are a common cause of congenital cataracts.

Purpose of the Study:

• To investigate the presence and function of the intracellular pocket in Cx50.
• To understand how Cx50 intracellular pocket alterations impact channel activity.

Main Methods:

• Molecular dynamics simulations to identify the Cx50 intracellular pocket.
• Site-directed mutagenesis to alter key residues (R33, E162) in the pocket.
• Assays for gap junction communication and hemichannel activity.

Main Results:

• The intracellular pocket was identified in Cx50 hemichannels.
• Altering a salt bridge (R33-E162) disrupted gap junction plaques and communication.
• Mutations led to non-functional gap junctions but highly active hemichannels.

Conclusions:

• Intracellular pocket interactions are crucial for both gap junction and hemichannel function.
• Disruptions in Cx50's intracellular pocket may underlie congenital cataract development.