Kv 1.1 is associated with neuronal apoptosis and modulated by protein kinase C in the rat cerebellar granule cell

Previously, we reported that apoptosis of cerebellar granular neurons induced by low-K+ and serum-free (LK-S) was associated with an increase in the A-type K+ channel current (I-A), and an elevated expression of main alpha-subunit of the I-A channel, which is known as Kv4.2 and Kv4.3. Here, we show, as assessed by quantitative RT-PCR and whole-cell recording, that besides Kv4.2 and Kv4.3, Kv1.1 is very important for I-A channel. The expression of Kv1.1 was elevated in the apoptotic neurons, while silencing Kv1.1 expression by siRNA reduced the I-A amplitude of the apoptotic neuron, and increased neuron viability. Inhibiting Kv1.1 current by dendrotoxin-K evoked a similar effect of reduction of I-A amplitude and protection of neurons. Applying a protein kinase C (PKC) activator, phorbol ester acetate A (PMA) mimicked the LK-S-induced neuronal apoptotic effect, enhanced the I-A amplitude and reduced the granule cell viability. The PKC inhibitor, bisindolylmaleimide I and Go6976 protected the cell against apoptosis induced by LK-S. After silencing the Kv1.1 gene, the effect of PMA on the residual K+ current was reduced significantly. Quantitative RT-PCR and Western immunoblot techniques revealed that LK-S treatment and PMA increased the level of the expression of Kv1.1, in contrast, bisindolylmaleimide I inhibited Kv1.1 expression. In addition, the activation of the PKC isoform was identified in apoptotic neurons. We thus conclude that in the rat cerebellar granule cell, the I-A channel associated with apoptotic neurons is encoded mainly by the Kv1.1 gene, and that the PKC pathway promotes neuronal apoptosis by a brief modulation of the I-A amplitude and a permanent increase in the levels of expression of the Kv1.1 alpha-subunit.