| First Author | Stepanyan R | Year | 2009 |
| Journal | J Neurosci | Volume | 29 |
| Issue | 13 | Pages | 4023-34 |
| PubMed ID | 19339598 | Mgi Jnum | J:147447 |
| Mgi Id | MGI:3840739 | Doi | 10.1523/JNEUROSCI.4566-08.2009 |
| Citation | Stepanyan R, et al. (2009) Fast adaptation and Ca2+ sensitivity of the mechanotransducer require myosin-XVa in inner but not outer cochlear hair cells. J Neurosci 29(13):4023-34 |
| abstractText | In inner ear hair cells, activation of mechanotransduction channels is followed by extremely rapid deactivation that depends on the influx of Ca(2+) through these channels. Although the molecular mechanisms of this 'fast' adaptation are largely unknown, the predominant models assume Ca(2+) sensitivity as an intrinsic property of yet unidentified mechanotransduction channels. Here, we examined mechanotransduction in the hair cells of young postnatal shaker 2 mice (Myo15(sh2/sh2)). These mice have no functional myosin-XVa, which is critical for normal growth of mechanosensory stereocilia of hair cells. Although stereocilia of both inner and outer hair cells of Myo15(sh2/sh2) mice lack myosin-XVa and are abnormally short, these cells have dramatically different hair bundle morphology. Myo15(sh2/sh2) outer hair cells retain a staircase arrangement of the abnormally short stereocilia and prominent tip links. Myo15(sh2/sh2) inner hair cells do not have obliquely oriented tip links, and their mechanosensitivity is mediated exclusively by 'top-to-top' links between equally short stereocilia. In both inner and outer hair cells of Myo15(sh2/sh2) mice, we found mechanotransduction responses with a normal 'wild-type' amplitude and speed of activation. Surprisingly, only outer hair cells exhibit fast adaptation and sensitivity to extracellular Ca(2+). In Myo15(sh2/sh2) inner hair cells, fast adaptation is disrupted and the transduction current is insensitive to extracellular Ca(2+). We conclude that the Ca(2+) sensitivity of the mechanotransduction channels and the fast adaptation require a structural environment that is dependent on myosin-XVa and is disrupted in Myo15(sh2/sh2) inner hair cells, but not in Myo15(sh2/sh2) outer hair cells. |
