HCN1 and HCN2 proteins are expressed in cochlear hair cells: HCN1 can form a ternary complex with protocadherin 15 CD3 and f-actin-binding filamin a or can interact with HCN2

Background: Protein-protein interaction between HCN1 and tip-link protocadherin 15CD3 suggests a role for HCN1 in hair-cell mechanotransduction. Results: HCN1 and HCN2 form alternate ternary protein complexes with hair-cell stereociliary proteins. Conclusion: Alternate protein-protein interactions reflect separation of binding events for stereociliary proteins implicated in mechanotransduction. Significance: HCN1 is the only channel component identified as binding to a stereociliary tip-link protein.