# Binding of PCDH15 to TMC1 for Mechanosensation in the Inner Ear

> **NIH NIH F32** · HARVARD MEDICAL SCHOOL · 2022 · $67,582

## Abstract

Project Summary
At the tip of each stereocilium in the hair bundle of vertebrate hair cells is a mechanotransduction
complex that mediates the conversion of sound and head movements into the senses of hearing
and balance, respectively. TMC1, a ten‐pass transmembrane (TM) protein with homology to
TMEM16 and OSCA ion channels, has recently been identified as a pore‐forming, ion channel
subunit of the complex. Protocadherin 15 (PCDH15) and cadherin 23 (CDH23) bind to form a
tetrameric, double‐stranded protein filament, the `tip link' that physically connects the
mechanotransduction complex to the side of a taller, neighboring stereocilia. Deflection of the
hair bundle increases tension along the tip link, pulling on the complex to open TMC1. It has
recently been shown through co‐immunoprecipitation (co‐IP) experiments that PCDH15 and
TMC1 physically interact, yet it not known specifically how.
This project aims to identify individual residues within TMC1 and PCDH 15 that facilitate
binding and that enable tension to gate the TMC1 channel. Biolayer interferometry and co‐IP
analysis of chimeric TMC1 and PCDH15 proteins will reveal which general regions are involved
in binding. Site‐directed mutagenesis will narrow the binding interface to specific residues. If
necessary, cross‐linking mass spectrometry will reveal residue‐to‐residue contacts in intracellular
and extracellular loops. If binding occurs within the membrane, a classic tryptophan scanning
protocol will be employed on the single TM helix of PCDH 15 to find residues essential for
interaction with TMC1. Finally, non‐binding TMC1 mutants and controls will be expressed in a
TMC1/TMC2 double knockout mouse model to determine if mutants localize properly to the tips
of hair bundle stereocilia but fail to mediate mechanotransduction.

## Key facts

- **NIH application ID:** 10375541
- **Project number:** 5F32DC018713-03
- **Recipient organization:** HARVARD MEDICAL SCHOOL
- **Principal Investigator:** Charles Brown Phillips
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $67,582
- **Award type:** 5
- **Project period:** 2020-04-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10375541

## Citation

> US National Institutes of Health, RePORTER application 10375541, Binding of PCDH15 to TMC1 for Mechanosensation in the Inner Ear (5F32DC018713-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10375541. Licensed CC0.

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