FIGURE 3.
Effect of CTTN depletion and overexpression on KV10.1-mediated current. Representative current traces of KV10.1 expressed in Xenopus oocytes under control conditions (Control), depleted (PTO; via injection of an antisense oligonucleotide) or increased (CTTN; via overexpression) CTTN levels are shown. Test pulses were applied ranging from the holding potential of −100 to +80 mV in 20-mV increments evoked whole cell currents. To determine the current-voltage relationship, the steady state current (I) was measured at the end of each pulse and normalized to the recorded current at +80 mV (Imax). Increased or decreased levels of CTTN (PTO or CTTN, respectively) do not have any effect on the general characteristic current appearance (A) or on current-voltage relationships (B). C, KV10.1 currents were evoked with a test pulse to +40 mV starting from either a holding potential of −100 or −70 mV. As expected for KV10.1, the activation of current depended on the prepulse potential independent of CTTN expression levels. D and E, depletion of CTTN (PTO) significantly decreased current amplitudes at a test pulse of +80 mV in comparison to control levels. This effect was dependent on the amount of PTO injected (D). Overexpression of human CTTN was not able to increase current amplitudes over control levels significantly, but partially restored current amplitudes in PTO injected oocytes (E). F, incubation for 24 h with the Arp2/3 inhibitor CK-666 (50 μm) did not alter the current amplitude in oocytes expressing KV10.1. Current amplitude was determined at the end of a depolarization to +60 mV.