Abstract 201: Overexpression of Calcium/Calmodulin-Dependent Protein Kinase II (CaMKII) Potentiates Angiotensin II (AngII)-Mediated Signaling in Neurons

Abstract

AngII signaling in the brain regulates systemic cardiovascular function. AngII modulates neuronal ion channel activity and neuronal firing via reactive oxygen species (ROS) and redox-sensitive proteins. Our recent studies indicate that in neurons AngII increases activity (i.e. phosphorylation) of CaMKII, a signaling intermediate known to inhibit potassium (K+) channel current. However, the potential cross-talk between AngII, ROS, and CaMKII in modulating neuronal K+ channel activity and the in vivo central AngII-induced pressor response remains unclear. Here, we tested the hypothesis that CaMKII overexpression exacerbates the AngII-dependent inhibition of K+ channel current and the acute central AngII-induced increase in blood pressure. The neuron specific isoform of CaMKII (CaMKIIα) was cloned, and CaMKIIα adenovirus was generated (AdCaMKIIα). Adenovirus-mediated overexpression of total and active CaMKII protein were assessed in differentiated mouse catecholaminergic (CATH.a) neurons by measuring total and phosphorylated CaMKII protein levels, respectively, via Western blot analysis. To investigate the effect of CaMKIIα overexpression on K+ channel activity, CATH.a neurons were transduced with AdCaMKIIα or control adenovirus, AdEmpty, and voltage-gated K+ current (IKV) was measured by the whole cell patch-clamp technique. Baseline IKV was measured followed by 5 mins of AngII (100 nM) superfusion. AngII lowered steady-state current (ISS) and peak current (Ipeak) in AdEmpty-transduced neurons (ISS by 20 ± 4%; Ipeak by 19 ± 3%), and this inhibitory response was significantly potentiated in AdCaMKIIα-transduced neurons (ISS by 40 ± 7%; Ipeak by 41 ± 5%; p< 0.05). Preliminary in vivo studies suggest that the central AngII-induced pressor response is exacerbated in mice intracerebroventricularly injected with AdCaMKIIα as compared to control virus-injected mice. These data indicate that CaMKIIα overexpression potentiates AngII-mediated inhibition of IKv and the central AngII-induced pressor response. Future studies will investigate the ROS-mediated post-translational modifications of CaMKIIα in AngII-stimulated neurons and the contribution of these modifications to ion channel activity and blood pressure regulation.