Abstract
A-type channels, encoded by the pore-forming alpha-subunits of the Kv4.x family, are particularly important in regulating membrane excitability in the CNS and the heart. Given the key role of modulation of A currents by kinases, we sought to investigate the protein structure-function relationships underlying the regulation of these currents by PKA. We have previously shown the existence of two PKA phosphorylation sites in the Kv4.2 sequence; therefore, we focused this study on the Kv4.2 primary subunit. In the present studies we made the surprising finding that PKA phosphorylation of the Kv4.2 alpha-subunit is necessary but not sufficient for channel modulation; channel modulation by PKA required the presence of an ancillary subunit, the K+ channel interacting protein (KChIP3). Therefore, these findings indicate a surprising complexity to kinase regulation of A currents, in that an interaction of two separate molecular events, alpha-subunit phosphorylation and the association of an ancillary subunit (KChIP3), are necessary for phosphorylation-dependent regulation of Kv4.2-encoded A channels by PKA. Overall, our studies indicate that PKA must of necessity act on a supramolecular complex of pore-forming alpha-subunits plus ancillary subunits to alter channel properties.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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8-Bromo Cyclic Adenosine Monophosphate / pharmacology
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Amino Acid Substitution
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Animals
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Binding Sites / genetics
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COS Cells
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Calcium-Binding Proteins / genetics
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Calcium-Binding Proteins / metabolism
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Colforsin / analogs & derivatives*
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Colforsin / pharmacology
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Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
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Cyclic AMP-Dependent Protein Kinases / metabolism*
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology
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Kv Channel-Interacting Proteins
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Macromolecular Substances
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Mutagenesis, Site-Directed
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Oocytes / drug effects
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Oocytes / metabolism
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Patch-Clamp Techniques
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Phosphopeptides / metabolism
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Phosphorylation
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Potassium Channels / genetics
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Potassium Channels / metabolism*
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Potassium Channels, Voltage-Gated*
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Protein Subunits / metabolism
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Repressor Proteins*
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Shal Potassium Channels
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Structure-Activity Relationship
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Transfection
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Xenopus laevis
Substances
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Calcium-Binding Proteins
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Enzyme Inhibitors
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Kv Channel-Interacting Proteins
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Macromolecular Substances
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Phosphopeptides
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Potassium Channels
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Potassium Channels, Voltage-Gated
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Protein Subunits
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Repressor Proteins
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Shal Potassium Channels
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Colforsin
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8-Bromo Cyclic Adenosine Monophosphate
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Cyclic AMP-Dependent Protein Kinases
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1,9-dideoxyforskolin