Modulation of delayed rectifier potassium channels by α 1-adrenergic activation via protein kinase C ζ and p62 in PC12 cells

Abstract

When PC12 cells are exposed to nerve growth factor (NGF), they extend neurites and express autonomic ganglion cell properties. We have previously shown that NGF is capable of inducing p62 expression, enabling the formation of the protein kinase C ζ (PKCζ)-p62-Kvβ (β-subunit of delayed rectifier K + channel) complex, a Kv channel-modulating complex. The formation of this complex results in the shifting of the Kv channel activation curve to the left via PKCζ activity. During the experiments, we noted that PC12 cells in a high-density culture exhibited a Kv channel activation curve shift similar to that observed in the NGF-treated cells. Therefore, we hypothesized that catecholamines released from PC12 cells may induce p62 expression. In order to test this idea, cells in a low-density culture were treated for 24 h with norepinephrine (NE). In these cells, we noted a leftward shift of the activation curve. The presence of the α 1-adrenergic antagonist specifically prevented the effects of NE. Pre-treatment of the low-density cells with α 1-agonists induced changes similar to those associated with NE, confirming that NE modulates Kv channels via the α 1-adrenergic receptor. NE's effects were blocked by treatment with PKCζ specific inhibitors. Using Western blotting, we observed increased levels of p62 expression in both the high-density cells and the NE-treated low-density cells. These results suggest that locally secreted NE induces an increase in p62 expression, and also exerts a modulatory effect on Kv channels via the PKCζ-p62-Kvβ channel modulating complex.