A fundamental role for KChIPs in determining the molecular properties and trafficking of Kv4.2 potassium channels.
Kv4 potassium channels regulate action potentials in neurons and cardiac myocytes. Co-expression of EF hand-containing Ca2+-binding proteins termed KChIPs with pore-forming Kv4 alpha subunits causes changes in the gating and amplitude of Kv4 currents (An, W. F., Bowlby, M. R., Betty, M., Cao, J., Ling, H. P., Mendoza, G., Hinson, J. W., Mattsson, K. I., Strassle, B. W., Trimmer, J. S., and Rhodes, K. J. (2000) Nature 403, 553-556). Here we show that KChIPs profoundly affect the intracellular trafficking and molecular properties of Kv4.2 alpha subunits. Co-expression of KChIPs1-3 causes a dramatic redistribution of Kv4.2, releasing intrinsic endoplasmic reticulum retention and allowing for trafficking to the cell surface. KChIP co-expression also causes fundamental changes in Kv4.2 steady-state expression levels, phosphorylation, detergent solubility, and stability that reconstitute the molecular properties of Kv4.2 in native cells. Interestingly, the KChIP4a isoform, which exhibits unique effects on Kv4 channel gating, does not exert these effects on Kv4.2 and negatively influences the impact of other KChIPs. We provide evidence that these KChIP effects occur through the masking of an N-terminal Kv4.2 hydrophobic domain. These studies point to an essential role for KChIPs in determining both the biophysical and molecular characteristics of Kv4 channels and provide a molecular basis for the dramatic phenotype of KChIP knockout mice.
Shibata
Riichi
R
Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, New York 11794, USA.
Misonou
Hiroaki
H
Campomanes
Claire R
CR
Anderson
Anne E
AE
Schrader
Laura A
LA
Doliveira
Lisa C
LC
Carroll
Karen I
KI
Sweatt
J David
JD
Rhodes
Kenneth J
KJ
Trimmer
James S
JS
D000818:Animals; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D015151:Immunoblotting; D051605:Kv Channel-Interacting Proteins; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D051381:Rats; D012097:Repressor Proteins; D012694:Serine / Q000737:chemistry; D051672:Shal Potassium Channels; D013997:Time Factors; D014162:Transfection
D002135:Calcium-Binding Proteins; C496756:Csen protein, mouse; D003902:Detergents; C497019:Kcnd2 protein, mouse; C497020:Kcnd2 protein, rat; C496754:Kcnip1 protein, mouse; C496757:Kcnip1 protein, rat; C496755:Kcnip2 protein, mouse; C496758:Kcnip2 protein, rat; C496760:Kcnip3 protein, rat; D051605:Kv Channel-Interacting Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D020033:Protein Isoforms; D011500:Protein Synthesis Inhibitors; D012097:Repressor Proteins; D051672:Shal Potassium Channels; D012694:Serine; D003513:Cycloheximide; D002118:Calcium