Casein kinase 2 determines the voltage dependence of the Kv3.1 channel in auditory neurons and transfected cells.
The Kv3.1 potassium channel can be distinguished from most other delayed rectifier channels by its very high threshold of activation and lack of use-dependent inactivation. This allows neurons that express this channel to fire at very high frequencies. We have now found that this feature of the Kv3.1 channel is strongly influenced by its constitutive phosphorylation by the enzyme casein kinase II. Using stably transfected Chinese hamster ovary cells expressing Kv3.1, we show that Kv3.1 is highly phosphorylated under basal conditions. Whole-cell patch clamp recordings were used to characterize the electrophysiological consequence of dephosphorylation using alkaline phosphatase. This enzyme produced an increase in whole-cell conductance and shifted the voltage dependence of activation to more negative potentials by >20 mV. In addition, a similar shift in the voltage dependence of inactivation was observed. These findings were also confirmed in native Kv3.1 channels expressed in medial nucleus of the trapezoid body (MNTB) neurons. Furthermore, inhibitors of casein kinase 2 mimicked the effect of phosphatase treatment on voltage-dependent activation and inactivation, whereas inhibitors of protein kinase C failed to alter these parameters. The combination of biochemical and electrophysiological evidence suggests that the biophysical characteristics of Kv3.1 that are important to its role in MNTB neurons, allowing them to follow high-frequency stimuli with fidelity, are largely determined by phosphorylation of the channel.
Macica
C M
CM
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520-8066, USA.
Kaczmarek
L K
LK
D000469:Alkaline Phosphatase / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001306:Auditory Pathways / Q000166:cytology / Q000378:metabolism*; D001665:Binding Sites / Q000187:drug effects; D001933:Brain Stem / Q000166:cytology / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D016466:CHO Cells; D047390:Casein Kinase II; D006224:Cricetinae; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation / Q000187:drug effects; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D051670:Shaw Potassium Channels; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
D004791:Enzyme Inhibitors; D009479:Neuropeptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051670:Shaw Potassium Channels; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D000469:Alkaline Phosphatase; D013755:Tetradecanoylphorbol Acetate