Connexin 33 impairs gap junction functionality by accelerating connexin 43 gap junction plaque endocytosis

Area of Science:

• Cell Biology
• Molecular Biology
• Reproductive Biology

Background:

• Connexin 33 (Cx33) is a testis-specific protein influencing gap junction communication.
• Cx33 can negatively impact intercellular communication by affecting Cx43 trafficking in Sertoli cells.
• The precise molecular mechanisms behind Cx33's dominant-negative effect remain unclear.

Purpose of the Study:

• To investigate the molecular mechanisms by which Cx33 exerts its dominant-negative effect on gap junction function.
• To analyze the trafficking and interaction of Cx33 and Cx43 in Sertoli cells.
• To determine the role of Cx33 in the formation and function of heteromeric gap junctions.

Main Methods:

• Transfection of wild-type Sertoli cells with Cx33-DsRed2 and Cx43-green fluorescent protein vectors.
• Fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer (FLIM-FRET) and videomicroscopy.
• Immunoprecipitation assays to analyze protein-protein interactions.

Main Results:

• Cx33 and Cx43 form heteromeric oligomers that traffic to the plasma membrane via microtubules.
• Gap junction plaques containing Cx33 were found to be non-functional.
• Cx33 interacts with zonula occludens-1 (ZO-1) and alters its association with Cx43, particularly phosphorylated isoforms.
• Reduced ZO-1 signal at the membrane was observed in cells expressing Cx33.

Conclusions:

• Cx33 and Cx43 form non-functional heteromeric gap junctions.
• Cx33's dominant-negative effect may stem from its disruption of the Cx43/ZO-1 interaction.
• This altered association impacts ZO-1 localization and potentially gap junction plaque stability and function.