PKA modulation of Kv4.2-encoded A-type potassium channels requires formation of a supramolecular complex.
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.
Schrader
Laura A
LA
Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA.
Anderson
Anne E
AE
Mayne
Amber
A
Pfaffinger
Paul J
PJ
Sweatt
John David
JD
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005576:Colforsin / Q000031:analogs & derivatives* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051605:Kv Channel-Interacting Proteins; D046911:Macromolecular Substances; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010748:Phosphopeptides / Q000378:metabolism; D010766:Phosphorylation; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits / Q000378:metabolism; D012097:Repressor Proteins; D051672:Shal Potassium Channels; D013329:Structure-Activity Relationship; D014162:Transfection; D014982:Xenopus laevis
D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D051605:Kv Channel-Interacting Proteins; D046911:Macromolecular Substances; D010748:Phosphopeptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D012097:Repressor Proteins; D051672:Shal Potassium Channels; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D017868:Cyclic AMP-Dependent Protein Kinases; C047983:1,9-dideoxyforskolin