Identification and localization of an arachidonic acid-sensitive potassium channel in the cochlea.
Receptor cells of the auditory and vestibular end organs of vertebrates acquire various types of potassium channels during development. Their expression and kinetics can differ along the tonotopic axis as well as in different cell types of the sensory epithelium. These variations can play a crucial role in modulating sensory transduction and cochlear tuning. Whole-cell tight-seal recordings of isolated hair cells revealed the presence of an arachidonic acid-sensitive A-type channel in the short (outer) hair cells of the chicken cochlea. This polyunsaturated fatty acid blocked the A-current, thereby increasing the amplitude and duration of the voltage response in these cells. We identified the gene encoding this channel as belonging to a member of the Shal subfamily, Kv4.2. Expression of the recombinant channel shows half-activation and inactivation potentials shifted to more positive values relative to native channels, suggesting that the native channel is coexpressed with an accessory subunit. RT-PCR revealed that transcription begins early in development, whereas in situ hybridization showed mRNA expression limited to the intermediate and short hair cells located in specific regions of the adult cochlea. Additional localization, using immunofluorescent staining, revealed clustering in apical-lateral regions of the receptor cell as well as in the cochlear ganglion. These experiments provide evidence that in addition to membrane proteins modulating excitation in these receptor cells, fatty acids contribute to the coding of auditory stimuli via these channels.
Sokolowski
Bernd H A
BH
Department of Otolaryngology-Head and Neck Surgery, University of South Florida, Tampa, Florida 33612, USA. bsokolow@hsc.usf.edu
Sakai
Yoshihisa
Y
Harvey
Margaret C
MC
Duzhyy
Dmytro E
DE
D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001483:Base Sequence; D016466:CHO Cells; D002642:Chick Embryo; D002645:Chickens; D003051:Cochlea / Q000196:embryology / Q000254:growth & development; D006224:Cricetinae; D003412:Cricetulus; D018076:DNA, Complementary / Q000235:genetics; D015723:Gene Library; D018072:Hair Cells, Auditory, Outer / Q000737:chemistry* / Q000196:embryology; D017403:In Situ Hybridization; D015640:Ion Channel Gating / Q000187:drug effects; D008969:Molecular Sequence Data; D005810:Multigene Family; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D012333:RNA, Messenger / Q000032:analysis; D011993:Recombinant Fusion Proteins / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D018076:DNA, Complementary; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D015117:5,8,11,14-Eicosatetraynoic Acid; D016718:Arachidonic Acid