Cloning and characterization of SK2 channel from chicken short hair cells.
In the inner ear of birds, as in mammals, reptiles and amphibians, acetylcholine released from efferent neurons inhibits hair cells via activation of an apamin-sensitive, calcium-dependent potassium current. The particular potassium channel involved in avian hair cell inhibition is unknown. In this study, we cloned a small-conductance, calcium-sensitive potassium channel (gSK2) from a chicken cochlear library. Using RT-PCR, we demonstrated the presence of gSK2 mRNA in cochlear hair cells. Electrophysiological studies on transfected HEK293 cells showed that gSK2 channels have a conductance of approximately 16 pS and a half-maximal calcium activation concentration of 0.74+/-0.17 microM. The expressed channels were blocked by apamin (IC(50)=73.3+/-5.0 pM) and d-tubocurarine (IC(50)=7.6+/-1.0 microM), but were insensitive to charybdotoxin. These characteristics are consistent with those reported for acetylcholine-induced potassium currents of isolated chicken hair cells, suggesting that gSK2 is involved in efferent inhibition of chicken inner ear. These findings imply that the molecular mechanisms of inhibition are conserved in hair cells of all vertebrates.
Matthews
T M
TM
Department of Biomedical Engineering, The Center for Hearing Sciences, Johns Hopkins University School of Medicine, 521 Traylor Building, 720 Rutland Ave., Baltimore, MD 21205-2195, USA.
Duncan
R K
RK
Zidanic
M
M
Michael
T H
TH
Fuchs
P A
PA
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001030:Apamin / Q000494:pharmacology; D015139:Blotting, Southern / Q000379:methods; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D002645:Chickens; D003001:Cloning, Molecular / Q000379:methods; D003051:Cochlea / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D015723:Gene Library; D006198:Hair Cells, Auditory / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008969:Molecular Sequence Data; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D051640:Small-Conductance Calcium-Activated Potassium Channels; D014162:Transfection / Q000379:methods; D014403:Tubocurarine / Q000494:pharmacology
C496897:KCNN2 protein, human; C496898:Kcnn2 protein, mouse; C496899:Kcnn2 protein, rat; D018733:Nicotinic Antagonists; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D051640:Small-Conductance Calcium-Activated Potassium Channels; D001030:Apamin; D002118:Calcium; D014403:Tubocurarine