TMHS Is an Integral Component of the Mechanotransduction Machinery of Cochlear Hair Cells

Abstract

SUMMARY Hair cells are mechanosensors for the perception of sound, acceleration and fluid motion. Mechanotransduction channels in hair cells are gated by tip links, which connect the stereocilia of a hair cell in the direction of their mechanical sensitivity. The molecular constituents of the mechanotransduction channels of hair cells are not known. Here we show that mechanotransduction is impaired in mice lacking the tetraspan TMHS. TMHS binds to the tip-link component PCDH15 and regulates tip-link assembly, a process that is disrupted by deafness-causing Tmhs mutations. TMHS also regulates transducer channel conductance and is required for fast channel adaptation. TMHS therefore resembles other ion channel regulatory subunits such as the TARPs of AMPA receptors that facilitate channel transport and regulate the properties of pore-forming channel subunits. We conclude that TMHS is an integral component of the hair cells mechanotransduction machinery that functionally couples PCDH15 to the transduction channel.

Functional Analysis of the Transmembrane and Cytoplasmic Domains of Pcdh15a in Zebrafish Hair Cells

“…In mice, mutations or deletions of Lhfpl5, Myo7a, and Ush1c cause the reduction or mislocalization of PCDH15 in stereocilia (Senften et al, 2006;Yan et al, 2011;Xiong et al, 2012). In agreement with previous findings, we observed that Pcdh15-CD3-EGFP is absent at the tips of mature hair bundles in lhfpl5a, myo7aa, and cdh23 mutant fish.…”

“…The cytoplasmic tail of PCDH15 has been shown to interact in vitro or in heterologous experiments with a number of proteins implicated in mechanotransduction, including LHFPL5, MYO7A, and a PDZ-containing protein, USH1C (also known as Harmonin) (El-Amraoui and Petit, 2005;Yan and Liu, 2010;Xiong et al, 2012). In mice, mutations or deletions of Lhfpl5, Myo7a, and Ush1c cause the reduction or mislocalization of PCDH15 in stereocilia (Senften et al, 2006;Yan et al, 2011;Xiong et al, 2012).…”

“…Some of these genes, such as Cdh23, Lhfpl5, and Myo7a, have been shown to affect the localization of PCDH15 in stereocilia (Senften et al, 2006;Xiong et al, 2012). To determine whether EGFPtagged Pcdh15a protein also exhibits the same requirements for localization, we imaged Pcdh15a-CD3-EGFP in lhfpl5a tm290d , cdh23 nl9 , and myo7aa ty220d mutant hair cells.…”

Rescue of Hearing by Gene Delivery to Inner-Ear Hair Cells Using Exosome-Associated AAV

“…LHFPL5 protein is an integral component of the mechanotransduction machinery in both OHCs and IHCs, and its absence leads to early hair cell degeneration, profound deafness, and severe vestibular dysfunction. 18 Because this model is on the C57BL/6 background and our previous gene transfer experiments were performed on CD1 mice, we tested whether exo-AAV transduces hair cells with the same efficiency on the C57BL/6 background. We did not observe any differences between CD1 and C57BL/6 transduction rates using exo-AAV1-GFP ( Figure S5).…”

Clarin-1 acts as a modulator of mechanotransduction activity and presynaptic ribbon assembly

“…These proteins form multimolecular complexes creating an intricate network in which signaling molecules complex together giving origin to subcellular structures known as the tetraspan-enriched microdomains. Thus, by integrating different signaling pathway components, these small transmembrane proteins act as modulators of the signaling cascade and, ultimately, of cell homeostasis (Adato et al, 2002;Charrin et al, 2003;Chen et al, 2003;Xiong et al, 2012).…”