What they found
TL;DR (qwen3.6:35b): Cryo-EM analysis reveals that protocadherin 15 forms a right-handed double-helix dimer, providing the first direct structural evidence for the architecture of tip links. Mutations disrupting this dimerization interface impair mechanotransduction, confirming its functional importance.
Tip links connect the stereocilia of mechanosensory hair cells in the inner ear and transmit force onto mechanotransduction (MET) channels. Tip links consist of protocadherin 15 (PCDH15) and cadherin 23, which assemble into an extracellular filament approximately 150 nm in length. Rare freeze-etched electron microscopy (EM) images have suggested that tip links could be right-handed double helices in vivo, but direct structural evidence has been lacking. Using cryo-EM we determined the structure of a large part of the extracellular PCDH15 domain. Two PCDH15 molecules form a parallel cis dimer stabilized by several dimerization interfaces, including two strand crossovers and two parallel contacts, yielding a right-handed double helix. Functional studies show that mutations in PCDH15 dimerization-domains impair MET. Our results establish the molecular foundation for how PCDH15 forms a right-handed double helix to enable mechanical sensing.
How this applies to our program
This study clarifies the structural composition of the tip link complex, distinguishing the role of PCDH15 from STRC/DFNB16. Understanding how PCDH15 dimerizes to form the filament backbone helps isolate the specific mechanical and assembly defects caused by STRC mutations in hair cells.
Key numbers
- 150 nm length of the extracellular tip link filament
- 2 strand crossovers stabilizing the dimer
- 2 parallel contacts contributing to the dimerization interface
Links
Connections
[source]auto-indexed 2026-06-11 by strc-lit-watch