14-3-3θ is a Binding Partner of Rat Eag1 Potassium Channels

The ether-a-go-go (Eag) potassium (K+) channel belongs to the superfamily of voltage-gated K+ channel. In mammals, the expression of Eag channels is neuron-specific but their neurophysiological role remains obscure. We have applied the yeast two-hybrid screening system to identify rat Eag1 (rEag1)-interacting proteins from a rat brain cDNA library. One of the clones we identified was 14-3-3 theta, which belongs to a family of small acidic protein abundantly expressed in the brain. Data from in vitro yeast two-hybrid and GST pull-down assays suggested that the direct association with 14-3-3 theta was mediated by both the N- and the C-termini of rEag1. Co-precipitation of the two proteins was confirmed in both heterologous HEK293T cells and native hippocampal neurons. Electrophysiological studies showed that over-expression of 14-3-3 theta led to a sizable suppression of rEag1 K+ currents with no apparent alteration of the steady-state voltage dependence and gating kinetics. Furthermore, co-expression with 14-3-3 theta failed to affect the total protein level, membrane trafficking, and single channel conductance of rEag1, implying that 14-3-3 theta binding may render a fraction of the channel locked in a nonconducting state. Together these data suggest that 14-3-3 theta is a binding partner of rEag1 and may modulate the functional expression of the K+ channel in neurons.