Potassium Channel Subunits: The MiRP Family

The KCNE3-encoded peptide MiRP2 associates with the α-subunit Kv3.4 to generate VGK channel currents typical of skeletal myocytes.

A. The human gene for the α-subunit Kv3.4 can be expressed in CHO cells to generate functional VGK channels. Co-expression of MiRP2 is required, however, to generate a current that is typical of skeletal myocytes (right); note that MiRP2 leads to sub-threshold currents. Cells were held at -80 mV and depolarized for 3 s to voltages of -70 (red), -40 (green), -20 (yellow), 20 (purple), 40 (orange), 70 (blue), and 90 (black) mV. Kv3.4 currents were studied in on-cell patches with 100 mM external KCl.

B. Steady-state currents in patches held at –40 mV. The displayed traces represent 18-second continuous recordings at 6 s per line. (The patches representing expression of Kv3.4 and co-expression of Kv3.4/MiRP2 in CHO cells contain one channel; native C2C12 myocyte patches contain three channels.)