[HTML][HTML] Integrity and regeneration of mechanotransduction machinery regulate aminoglycoside entry and sensory cell death

AA Vu, GS Nadaraja, ME Huth, L Luk, J Kim, R Chai… - PLoS …, 2013 - journals.plos.org
AA Vu, GS Nadaraja, ME Huth, L Luk, J Kim, R Chai, AJ Ricci, AG Cheng
PLoS One, 2013journals.plos.org
Sound perception requires functional hair cell mechanotransduction (MET) machinery,
including the MET channels and tip-link proteins. Prior work showed that uptake of ototoxic
aminoglycosides (AG) into hair cells requires functional MET channels. In this study, we
examined whether tip-link proteins, including Cadherin 23 (Cdh23), regulate AG entry into
hair cells. Using time-lapse microscopy on cochlear explants, we found rapid uptake of
gentamicin-conjugated Texas Red (GTTR) into hair cells from three-day-old Cdh23+/+ and …
Sound perception requires functional hair cell mechanotransduction (MET) machinery, including the MET channels and tip-link proteins. Prior work showed that uptake of ototoxic aminoglycosides (AG) into hair cells requires functional MET channels. In this study, we examined whether tip-link proteins, including Cadherin 23 (Cdh23), regulate AG entry into hair cells. Using time-lapse microscopy on cochlear explants, we found rapid uptake of gentamicin-conjugated Texas Red (GTTR) into hair cells from three-day-old Cdh23+/+ and Cdh23v2J/+ mice, but failed to detect GTTR uptake in Cdh23v2J/v2J hair cells. Pre-treatment of wildtype cochleae with the calcium chelator 1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA) to disrupt tip-links also effectively reduced GTTR uptake into hair cells. Both Cdh23v2J/v2J and BAPTA-treated hair cells were protected from degeneration caused by gentamicin. Six hours after BAPTA treatment, GTTR uptake remained reduced in comparison to controls; by 24 hours, drug uptake was comparable between untreated and BAPTA-treated hair cells, which again became susceptible to cell death induced by gentamicin. Together, these results provide genetic and pharmacologic evidence that tip-links are required for AG uptake and toxicity in hair cells. Because tip-links can spontaneously regenerate, their temporary breakage offers a limited time window when hair cells are protected from AG toxicity.
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