Interactions between the C-terminus of Kv1.5 and Kv? regulate pyridine nucleotide-dependent changes in channel gating.

ABSTRACT: Voltage-gated potassium (Kv) channels are tetrameric assemblies of transmembrane Kv proteins with cytosolic N- and C-termini. The N-terminal domain of Kv1 proteins binds to ?-subunits, but the role of the C-terminus is less clear. Therefore, we studied the role of the C-terminus in regulating Kv1.5 channel and its interactions with Kv?-subunits. When expressed in COS-7 cells, deletion of the C-terminal domain of Kv1.5 did not affect channel gating or kinetics. Coexpression of Kv1.5 with Kv?3 increased current inactivation, whereas Kv?2 caused a hyperpolarizing shift in the voltage dependence of current activation. Inclusion of NADPH in the patch pipette solution accelerated the inactivation of Kv1.5-Kv?3 currents. In contrast, NADP(+) decreased the rate and the extent of Kv?3-induced inactivation and reversed the hyperpolarizing shift in the voltage dependence of activation induced by Kv?2. Currents generated by Kv1.5?C+Kv?3 or Kv1.5?C+Kv?2 complexes did not respond to changes in intracellular pyridine nucleotide concentration, indicating that the C-terminus is required for pyridine nucleotide-dependent interactions between Kv? and Kv1.5. A glutathione-S-transferase (GST) fusion protein containing the C-terminal peptide of Kv1.5 did not bind to apoKv?2, but displayed higher affinity for Kv?2:NADPH than Kv?2:NADP(+). The GST fusion protein also precipitated Kv? proteins from mouse brain lysates. Pull-down experiments, structural analysis and electrophysiological data indicated that a specific region of the C-terminus (Arg543-Val583) is required for Kv? binding. These results suggest that the C-terminal domain of Kv1.5 interacts with ?-subunits and that this interaction is essential for the differential regulation of Kv currents by oxidized and reduced nucleotides.

SUBMITTER: Tipparaju SM 

PROVIDER: S-EPMC3367765 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature