N-type inactivation features of Kv4.2 channel gating.
We examined whether the N-terminus of Kv4.2 A-type channels (4.2NT) possesses an autoinhibitory N-terminal peptide domain, which, similar to the one of Shaker, mediates inactivation of the open state. We found that chimeric Kv2.1(4.2NT) channels, where the cytoplasmic Kv2.1 N-terminus had been replaced by corresponding Kv4.2 domains, inactivated relatively fast, with a mean time constant of 120 ms as compared to 3.4 s in Kv2.1 wild-type. Notably, Kv2.1(4.2NT) showed features typically observed for Shaker N-type inactivation: fast inactivation of Kv2.1(4.2NT) channels was slowed by intracellular tetraethylammonium and removed by N-terminal truncation (Delta40). Kv2.1(4.2NT) channels reopened during recovery from inactivation, and recovery was accelerated in high external K+. Moreover, the application of synthetic N-terminal Kv4.2 and ShB peptides to inside-out patches containing slowly inactivating Kv2.1 channels mimicked N-type inactivation. Kv4.2 channels, after fractional inactivation, mediated tail currents with biphasic decay, indicative of passage through the open state during recovery from inactivation. Biphasic tail current kinetics were less prominent in Kv4.2/KChIP2.1 channel complexes and virtually absent in Kv4.2Delta40 channels. N-type inactivation features of Kv4.2 open-state inactivation, which may be suppressed by KChIP association, were also revealed by the finding that application of Kv4.2 N-terminal peptide accelerated the decay kinetics of both Kv4.2Delta40 and Kv4.2/KChIP2.1 patch currents. However, double mutant cycle analysis of N-terminal inactivating and pore domains indicated differences in the energetics and structural determinants between Kv4.2 and Shaker N-type inactivation.
Gebauer
Manuel
M
Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie der Universität Hamburg, 20246 Hamburg, Germany.
Isbrandt
Dirk
D
Sauter
Kathrin
K
Callsen
Britta
B
Nolting
Andreas
A
Pongs
Olaf
O
Bähring
Robert
R
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D007668:Kidney / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels; D013329:Structure-Activity Relationship
C497018:KCND2 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels