A C-terminal PDZ binding domain modulates the function and localization of Kv1.3 channels

The voltage-gated potassium channel, Kv1.3, plays an important role in regulating membrane excitability in diverse cell types ranging from T-lymphocytes to neurons. In the present study, we test the hypothesis that the C-terminal PDZ binding domain modulates the function and localization of Kv1.3. We created a mutant form of Kv1.3 that lacked the last three amino acids of the C-terminal PDZ-binding domain (Kv1.3ΔTDV). This form of Kv1.3 did not bind the PDZ domain containing protein, PSD95. We transfected wild type and mutant Kv1.3 into HEK293 cells and determined if the mutation affected current, Golgi localization, and surface expression of the channel. We found that cells transfected with Kv1.3ΔTDV had greater current and lower Golgi localization than those transfected with Kv1.3. Truncation of the C-terminal PDZ domain did not affect surface expression of Kv1.3. These findings suggest that PDZ-dependent interactions affect both Kv1.3 localization and function. The finding that current and Golgi localization changed without a corresponding change in surface expression suggests that PDZ interactions affect localization and function via independent mechanisms.