TMC1 and TMC2 Localize at the Site of Mechanotransduction in Mammalian Inner Ear Hair Cell Stereocilia

Kurima, Kiyoto; Ebrahim, Seham; Pan, Bifeng; Sedlacek, Miloslav; Sengupta, Prabuddha; Millis, Bryan A.; Cui, Runjia; Nakanishi, Hiroshi; Fujikawa, Taro; Kawashima, Yasunaru; Choi, Byung Yoon; Monahan, Kelly; Holt, Jeffrey R.; Griffith, Andrew J.; Kachar, Bechara

doi:10.1016/j.celrep.2015.07.058

Cited by 169 publications

(205 citation statements)

References 34 publications

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“…The following rabbit polyclonal, affinity purified primary custom made antibodies were obtained for the studies: anti-TMC2 (1:200, PB361) 44 , anti-whirlin (1:200, PB5140) 35 , anti-myosin XVa (1:50, PB48) 45 , anti-Eps8L2 (1:50, NP_073609.2) 46 and anti-Pcdh15 (1:200, HL5614) 5 . Secondary antibodies were: Alexa Fluor-405, 488, 546, or 647 goat anti-rabbit and Alexa Fluor-546, 555, or 647 goat anti-mouse (1:1000, Life Technologies).…”

Section: Methodsmentioning

confidence: 99%

CIB2 interacts with TMC1 and TMC2 and is essential for mechanotransduction in auditory hair cells

et al. 2017

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Inner ear hair cells detect sound through deflection of stereocilia, the microvilli-like projections that are arranged in rows of graded heights. Calcium and integrin-binding protein 2 is essential for hearing and localizes to stereocilia, but its exact function is unknown. Here, we have characterized two mutant mouse lines, one lacking calcium and integrin-binding protein 2 and one carrying a human deafness-related Cib2 mutation, and show that both are deaf and exhibit no mechanotransduction in auditory hair cells, despite the presence of tip links that gate the mechanotransducer channels. In addition, mechanotransducing shorter row stereocilia overgrow in hair cell bundles of both Cib2 mutants. Furthermore, we report that calcium and integrin-binding protein 2 binds to the components of the hair cell mechanotransduction complex, TMC1 and TMC2, and these interactions are disrupted by deafness-causing Cib2 mutations. We conclude that calcium and integrin-binding protein 2 is required for normal operation of the mechanotransducer channels and is involved in limiting the growth of transducing stereocilia.

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Section: Methodsmentioning

confidence: 99%

CIB2 interacts with TMC1 and TMC2 and is essential for mechanotransduction in auditory hair cells

et al. 2017

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“…These proteins are all likely to be involved in regulating actin polymerization at the top of the stereocilium and therefore dictating stereociliary height (182) (12) (71). The lower end of the tip link, formed by protocadherin-15, is also connected to the putative MET channel components TMC1 [transmembrane channel-like protein; (158) (135) (157) (78)], LHFPL5 [previously named TMHS for t etraspan m embrane protein of h air cell s tereocilia; (173) (312) (23)], and TMIE [ t rans m embrane i nner e ar; (98) (319)]. Protocadherin-15 falls into three isoform classes, CD1, CD2, and CD3, which have distinct carboxy termini (2) (302); the CD2 isoform is the native isoform in mammalian auditory hair cells (230), and it is the only isoform thought to interact with TMIE (319).…”

Section: Hair Cell Transductionmentioning

confidence: 99%

Hair Cell Transduction, Tuning, and Synaptic Transmission in the Mammalian Cochlea

Fettiplace

2017

Comprehensive Physiology

274

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Sound pressure fluctuations striking the ear are conveyed to the cochlea, where they vibrate the basilar membrane on which sit hair cells, the mechanoreceptors of the inner ear. Recordings of hair cell electrical responses have shown that they transduce sound via sub-micrometer deflections of their hair bundles, which are arrays of interconnected stereocilia containing the mechanoelectrical transducer (MET) channels. MET channels are activated by tension in extracellular tip links bridging adjacent stereocilia, and they can respond within microseconds to nanometer displacements of the bundle, facilitated by multiple processes of Ca2+-dependent adaptation. Studies of mouse mutants have produced much detail about the molecular organization of the stereocilia, the tip links and their attachment sites, and the MET channels localized to the lower ends of each tip link. The mammalian cochlea contains two categories of hair cells. Inner hair cells relay acoustic information via multiple ribbon synapses that transmit rapidly without rundown. Outer hair cells are important for amplifying sound-evoked vibrations. The amplification mechanism primarily involves contractions of the outer hair cells, which are driven by changes in membrane potential and mediated by prestin, a motor protein in the outer hair cell lateral membrane. Different sound frequencies are separated along the cochlea, with each hair cell being tuned to a narrow frequency range; amplification sharpens the frequency resolution and augments sensitivity 100-fold around the cell’s characteristic frequency. Genetic mutations and environmental factors such as acoustic overstimulation cause hearing loss through irreversible damage to the hair cells or degeneration of inner hair cell synapses.

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“…The channel proteins TMC 1 and 2 are part of a multi-subunit structure at the tips of each cilia [22] which is tethered to the side of an adjacent cilia by cadherin like proteins [23]. Sound induced vibrations lead to motion between adjacent cilia and activation of the tethered channels.…”

Section: Msc Gating Mechanisms and Molecular Identitymentioning

confidence: 99%

Piezo channels and GsMTx4: Two milestones in our understanding of excitatory mechanosensitive channels and their role in pathology

Suchyna

2017

Progress in Biophysics and Molecular Biology

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Discovery of Piezo channels and the reporting of their sensitivity to the inhibitor GsMTx4 were important milestones in the study of non-selective cationic mechanosensitive channels (MSCs) in normal physiology and pathogenesis. GsMTx4 had been used for years to investigate the functional role of cationic MSCs, especially in muscle tissue, but with little understanding of its target or inhibitory mechanism. The sensitivity of Piezo channels to bilayer stress and its robust mechanosensitivity when expressed in heterologous systems were keys to determining GsMTx4’s mechanism of action. However, questions remain regarding Piezo’s role in muscle function due to the non-selective nature of GsMTx4 inhibition toward membrane mechanoenzymes and the implication of MCS channel types by genetic knockdown. Evidence supporting Piezo like activity, at least in the developmental stages of muscle, is presented. While the MSC targets of GsMTx4 in muscle pathology are unclear, its muscle protective effects are clearly demonstrated in two recent in situ studies on normal cardiomyocytes and dystrophic skeletal muscle. The muscle protective function may be due to the combined effect of GsMTx4’s inhibitory action on cationic MSCs like Piezo and TRP, and its potentiation of repolarizing K+ selective MSCs like K2P and SAKCa. Paradoxically, the potent in vitro action of GsMTx4 on many physiological functions seems to conflict with its lack of in situ side-effects on normal animal physiology. Future investigations into cytoskeletal control of sarcolemma mechanics and the suspected inclusion of MSCs in membrane micro/nano sized domains with distinct mechanical properties will aide our understanding of this dichotomy.

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TMC1 and TMC2 Localize at the Site of Mechanotransduction in Mammalian Inner Ear Hair Cell Stereocilia

Cited by 169 publications

References 34 publications

CIB2 interacts with TMC1 and TMC2 and is essential for mechanotransduction in auditory hair cells

CIB2 interacts with TMC1 and TMC2 and is essential for mechanotransduction in auditory hair cells

Hair Cell Transduction, Tuning, and Synaptic Transmission in the Mammalian Cochlea

Piezo channels and GsMTx4: Two milestones in our understanding of excitatory mechanosensitive channels and their role in pathology

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