Figure 6.

AKAP79 regulation of Kv4.2 trafficking requires Kv4.2 PKA phosphorylation site S552. A, COS7 cells cotransfected Kv4.2 or Kv4.2^S552A and either control or AKAP79. Surface proteins were labeled with NHS-SS-Biotin and probed with mouse anti-Kv4.2 (1:2000). Cells coexpressing Kv4.2 and AKAP79 showed decreased surface expression of Kv4.2 compared with control. Surface expression of the Kv4.2 phospho-mutant S552A (Kv4.2^S552A) was not changed by AKAP79 coexpression. GAPDH served as a loading control. β-Actin is labeled as negative surface control. B, Pooled data normalized to total Kv4.2 expression show that AKAP79 coexpression decreased surface Kv4.2 expression by ∼40% (n = 5, p < 0.05), and without a significant effect on Kv4.2^S552A (n = 5, *p < 0.05). Error bars represent SEM. C, In electrophysiological recordings from COS7 cells, peak current density of Kv4.2-mediated currents increased (∼1.5-fold) by coexpression of AKAP79 with the phospho-mutant Kv4.2^S552A (n = 10) compared with Kv4.2 (n = 10). Ht31 application (15 min) significantly increased Kv4.2-mediated peak current density in the neurons cotransfected with Kv4.2 and AKAP79 (n = 10, p < 0.05), but this peak current density enhancement by Ht31 was not found in cells expressing Kv4.2^S552A and AKAP79 (n = 13, p < 0.05). Error bars represent SEM. Calibration: 200 pA, 200 ms.