title: The chloride-channel blocker 9-anthracenecarboxylic acid reduces the nonlinear capacitance of prestin-associated charge movement.
abstract: The basis of the extraordinary sensitivity and frequency selectivity of the cochlea is a chloride-sensitive protein called prestin which can produce an electromechanical response and which resides in the basolateral plasma membrane of outer hair cells (OHCs). The compound 9-anthracenecarboxylic acid (9-AC), an inhibitor of chloride channels, has been found to reduce the electromechanical response of the cochlea and the OHC mechanical impedance. To elucidate these 9-AC effects, the functional electromechanical status of prestin was assayed by measuring the nonlinear capacitance of OHCs from the guinea-pig cochlea and of prestin-transfected human embryonic kidney 293 (HEK 293) cells. Extracellular application of 9-AC caused reversible, dose-dependent and chloride-sensitive reduction in OHC nonlinear charge transfer, Qmax . Prestin-transfected cells also showed reversible reduction in Qmax . For OHCs, intracellular 9-AC application as well as reduced intracellular pH had no detectable effect on the reduction in Qmax by extracellularly applied 9-AC. In the prestin-transfected cells, cytosolic application of 9-AC approximately halved the blocking efficacy of extracellularly applied 9-AC. OHC inside-out patches presented the whole-cell blocking characteristics. Disruption of the cytoskeleton by preventing actin polymerization with latrunculin A or by decoupling of spectrin from actin with diamide did not affect the 9-AC-evoked reduction in Qmax . We conclude that 9-AC acts on the electromechanical transducer principally by interaction with prestin rather than acting via the cytoskeleton, chloride channels or pH. The 9-AC block presents characteristics in common with salicylate, but is almost an order of magnitude faster. 9-AC provides a new tool for elucidating the molecular dynamics of prestin function.
authors: Section of Physiological Acoustics and Communication, Faculty of Medicine, Eberhard Karls University Tübingen, 72076, Tübingen, Germany.
authors: Csaba
authors: C
authors: Harasztosi
authors: Section of Physiological Acoustics and Communication, Faculty of Medicine, Eberhard Karls University Tübingen, 72076, Tübingen, Germany.
authors: Anthony W
authors: AW
authors: Gummer
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D025802:Electric Capacitance; D006168:Guinea Pigs; D057809:HEK293 Cells; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008564:Membrane Potentials; D011506:Proteins / Q000378:metabolism*
chemical_list: D000873:Anthracenes; D018118:Chloride Channels; C498722:Pres protein, Cavia porcellus; D011506:Proteins; C010030:9-anthroic acid
keywords: auditory system; channelopathies; cochlea; electromechanical transduction; sensory hair cells