Integrity and regeneration of mechanotransduction machinery regulate aminoglycoside entry and sensory cell death.
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 Cdh23(v2J/+) mice, but failed to detect GTTR uptake in Cdh23(v2J/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 Cdh23(v2J/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.
Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California, USA.
Andrew A
AA
Vu
Garani S
GS
Nadaraja
Markus E
ME
Huth
Lauren
L
Luk
John
J
Kim
Renjie
R
Chai
Anthony J
AJ
Ricci
Alan G
AG
Cheng
D000617:Aminoglycosides / Q000378:metabolism*; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D016923:Cell Death; D002614:Chelating Agents / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives; D006198:Hair Cells, Auditory / Q000378:metabolism; D040542:Mechanotransduction, Cellular; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation
D000617:Aminoglycosides; D015820:Cadherins; C499091:Cdh23 protein, mouse; D002614:Chelating Agents; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium