The outer dynein arm assembly factor CCDC103 forms molecular scaffolds through multiple self-interaction sites

Area of Science:

• Cell Biology
• Structural Biology
• Biophysics

Background:

• CCDC103 protein is essential for outer dynein arm assembly in ciliary axonemes.
• Mutations in CCDC103 cause primary ciliary dyskinesia (PCD), a human genetic disorder.
• CCDC103 exhibits unusual biophysical properties, including oligomerization and microtubule binding.

Purpose of the Study:

• To biochemically identify the regions of CCDC103 responsible for protein self-interaction.
• To investigate the stability and nature of these CCDC103-CCDC103 interactions.
• To model the structural impact of a pathogenic mutation (H154P) in the RPAP3_C domain.

Main Methods:

• Biochemical assays to map CCDC103 self-interaction domains.
• Heat and reducing agent stability assays for protein interactions.
• Molecular modeling of the RPAP3_C domain.

Main Results:

• Two distinct regions mediating CCDC103 self-interaction were identified.
• These interactions are highly stable, resisting heat and detergent.
• One interaction involves an intrinsically disordered segment, the other the RPAP3_C domain.
• Data support the formation of an unconventional CCDC103 polymer.
• Structural consequences of the H154P mutation were elucidated.

Conclusions:

• CCDC103 self-interaction is mediated by stable interfaces, including an intrinsically disordered region and the RPAP3_C domain.
• These interactions likely facilitate the formation of an unconventional CCDC103 polymer essential for ciliary function.
• Understanding these interactions and mutation effects provides insight into primary ciliary dyskinesia pathogenesis.