casein-kinase-ii and Hypertension

Activity of the Epithelial Na

Topics: Amino Acid Substitution; Animals; Ankyrins; Biological Transport; Casein Kinase II; Chlorocebus aethiops; CHO Cells; COS Cells; Cricetulus; Epithelial Sodium Channels; Female; Hypertension; Male; Membrane Transport Proteins; Mice; Mice, Knockout; Nephrons; Phosphorylation; Protein Interaction Domains and Motifs; Signal Transduction; Sodium

Small conductance calcium-activated K(+) (SK) channels regulate neuronal excitability. However, little is known about changes in SK channel activity of pre-sympathetic neurons in the hypothalamic paraventricular nucleus (PVN) in essential hypertension. SK channels, calmodulin, and casein kinase II (CK2) form a molecular complex. Because CK2 is up-regulated in the PVN in spontaneously hypertensive rats (SHRs), we hypothesized that CK2 increases calmodulin phosphorylation and contributes to diminished SK channel activity in PVN pre-sympathetic neurons in SHRs. Perforated whole-cell recordings were performed on retrogradely labeled spinally projecting PVN neurons in Wistar-Kyoto (WKY) rats and SHRs. Blocking SK channels with apamin significantly increased the firing rate of PVN neurons in WKY rats but not in SHRs. CK2 inhibition restored the stimulatory effect of apamin on the firing activity of PVN neurons in SHRs. Furthermore, apamin-sensitive SK currents and depolarization-induced medium after-hyperpolarization potentials of PVN neurons were significantly larger in WKY rats than in SHRs. CK2 inhibition significantly increased the SK channel current and medium after-depolarization potential of PVN neurons in SHRs. In addition, CK2-mediated calmodulin phosphorylation level in the PVN was significantly higher in SHRs than in WKY rats. Although SK3 was detected in the PVN, its expression level did not differ significantly between SHRs and WKY rats. Our findings suggest that CK2-mediated calmodulin phosphorylation is increased and contributes to diminished SK channel function of PVN pre-sympathetic neurons in SHRs. This information advances our understanding of the mechanisms underlying hyperactivity of PVN pre-sympathetic neurons and increased sympathetic vasomotor tone in hypertension. Small conductance calcium-activated K(+) (SK) channels, calmodulin, and protein kinase CK2 form a molecular complex and regulate neuronal excitability. Our study suggests that augmented CK2 activity in hypertension can increase calmodulin (CaM) phosphorylation, which leads to diminished SK channel function in pre-sympathetic neurons. Diminished SK channel activity plays a role in hyperactivity of pre-sympathetic neurons in the hypothalamus in hypertension.

Topics: Animals; Blotting, Western; Calmodulin; Casein Kinase II; Hypertension; Male; Neurons; Paraventricular Hypothalamic Nucleus; Potassium Channels, Calcium-Activated; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Reverse Transcriptase Polymerase Chain Reaction; Sympathetic Nervous System

Increased glutamatergic input, particularly N-methyl-D-aspartate receptor (NMDAR) activity, in the paraventricular nucleus (PVN) of the hypothalamus is closely associated with high sympathetic outflow in essential hypertension. The molecular mechanisms underlying augmented NMDAR activity in hypertension are unclear. GluN2 subunit composition at the synaptic site critically determines NMDAR functional properties. Here, we found that evoked NMDAR-excitatory postsynaptic currents (EPSCs) of retrogradely labeled spinally projecting PVN neurons displayed a larger amplitude and shorter decay time in spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto (WKY) rats. Blocking GluN2B caused a smaller decrease in NMDAR-EPSCs of PVN neurons in SHRs than in WKY rats. In contrast, GluN2A blockade resulted in a larger reduction in evoked NMDAR-EPSCs and puff NMDA-elicited currents of PVN neurons in SHRs than in WKY rats. Blocking presynaptic GluN2A, but not GluN2B, significantly reduced the frequency of miniature EPSCs and the firing activity of PVN neurons in SHRs. The mRNA and total protein levels of GluN2A and GluN2B in the PVN were greater in SHRs than in WKY rats. Furthermore, the GluN2B Ser(1480) phosphorylation level and the synaptosomal GluN2A protein level in the PVN were significantly higher in SHRs than in WKY rats. Inhibition of protein kinase CK2 normalized the GluN2B Ser(1480) phosphorylation level and the contribution of GluN2A to NMDAR-EPSCs and miniature EPSCs of PVN neurons in SHRs. Collectively, our findings suggest that CK2-mediated GluN2B phosphorylation contributes to increased synaptic GluN2A, which potentiates pre- and postsynaptic NMDAR activity and the excitability of PVN presympathetic neurons in hypertension.

Topics: Animals; Casein Kinase II; Hypertension; Male; Neurons; Paraventricular Hypothalamic Nucleus; Phosphorylation; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, N-Methyl-D-Aspartate; Synaptic Potentials; Up-Regulation

Increased glutamatergic input in the paraventricular nucleus (PVN) is important for high sympathetic outflow in hypertension, but the associated molecular mechanisms remain unclear. Here, we determined the role of protein kinase CK2 (formerly casein kinase II) in increased N-methyl-d-aspartate receptor (NMDAR) activity in spinally projecting PVN neurons and sympathetic vasomotor tone in spontaneously hypertensive rats (SHRs). The selective CK2 inhibitors 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB) or 4,5,6,7-tetrabromobenzotriazole (TBB) significantly decreased the frequency of miniature EPSCs (mEPSCs) of labeled PVN neurons in SHRs but not in Wistar-Kyoto (WKY) normotensive rats. Also, DRB abolished the inhibitory effect of the NMDAR antagonist AP5 on the frequency of mEPSCs in SHRs. Treatment with DRB or TBB significantly reduced the amplitude of evoked NMDA-EPSCs but not AMPA-EPSCs in SHRs. Furthermore, DRB significantly decreased the firing activity of PVN neurons in SHRs but not in WKY rats. The membrane protein level of CK2α in the PVN, but not brainstem and prefrontal cortex, was significantly higher in SHRs than in WKY rats. Lowering blood pressure with celiac ganglionectomy in SHRs did not alter the increased CK2α level and the effects of DRB on mEPSCs and NMDA-EPSCs. In addition, intracerebroventricular injection of DRB not only significantly reduced blood pressure and lumbar sympathetic nerve discharges but also eliminated the inhibitory effect of AP5 microinjected into the PVN on sympathetic nerve activity in SHRs. Our findings suggest that augmented CK2 activity critically contributes to increased presynaptic and postsynaptic NMDAR activity in the PVN and elevated sympathetic vasomotor tone in essential hypertension.

Topics: Animals; Benzimidazoles; Blood Pressure; Brain Stem; Casein Kinase II; Dichlororibofuranosylbenzimidazole; Excitatory Postsynaptic Potentials; Ganglionectomy; Heart Rate; Hypertension; In Vitro Techniques; Injections, Intraventricular; Male; Microinjections; Paraventricular Hypothalamic Nucleus; Prefrontal Cortex; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Sympathetic Nervous System; Valine

The small G protein Rho signaling pathways are recognized as major regulators of cardiovascular functions, and activation of Rho proteins appears to be a common component for the pathogenesis of hypertension and vascular proliferative disorders. Recent evidence suggests that modulation of Rho protein signaling by phosphorylation of Rho proteins provides an additional simple mechanism for coordinating Rho protein functions. Phosphorylation of RhoA by cAMP- or cGMP-activated kinase on Ser188 induces cytosolic sequestration of RhoA through increased interaction with guanine dissociation inhibitor, thereby resulting in inhibition of RhoA-dependent functions. Here we show that stimulation of angiotensin II (Ang II) type 2 receptor (AT(2)R) in vascular smooth muscle cells induces Ser188 phosphorylation of RhoA independently of cAMP- or cGMP-activated kinase. We identify the Ser/Thr kinase Ste20-related kinase SLK as a new kinase phosphorylating RhoA on Ser188. Activation of the signaling cascade involving Src homology 2 domain-containing protein-tyrosine phosphatase 1, casein kinase II and SLK is responsible for RhoA phosphorylation and inhibition of RhoA-mediated arterial contraction induced by AT(2)R activation. These results thus identify the molecular mechanism linking AT(2)R to RhoA inhibition and vasodilation.

Topics: Angiotensin II; Animals; Aorta, Thoracic; Casein Kinase II; Cells, Cultured; Cyclic AMP-Dependent Protein Kinases; Cyclic GMP-Dependent Protein Kinases; Ethinyl Estradiol; Hypertension; Male; Megestrol Acetate; Muscle, Smooth, Vascular; Nitric Oxide Synthase; Phosphorylation; Protein Serine-Threonine Kinases; Protein Tyrosine Phosphatase, Non-Receptor Type 6; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor, Angiotensin, Type 2; rhoA GTP-Binding Protein; Signal Transduction; Up-Regulation; Vasoconstrictor Agents; Vasodilation