Casein Kinase 2-mediated Synaptic GluN2A Up-regulation Increases N-Methyl-d-aspartate Receptor Activity and Excitability of Hypothalamic Neurons in Hypertension

Zeng-You Ye,Li Li,De-Pei Li,Hui-Lin Pan

doi:10.1074/jbc.m111.331165

Abstract

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.

Highlights

We determined changes in GluN2 subunit composition responsible for increased N-methyl-D-aspartate receptor (NMDAR) activity in hypothalamus in hypertension
Shortened Decay Time of NMDAR-excitatory postsynaptic currents (EPSCs) of paraventricular nucleus (PVN) Neurons in spontaneously hypertensive rats (SHRs)—All whole cell patch clamp recordings were performed in retrogradely labeled PVN neurons in hypothalamic slices
The amplitude of NMDAR-EPSCs in labeled PVN neurons was significantly larger in 13-week-old SHRs than in age-matched WKY rats (Fig. 1, A and B)

Summary

Background

We determined changes in GluN2 subunit composition responsible for increased N-methyl-D-aspartate receptor (NMDAR) activity in hypothalamus in hypertension. We determined the contribution of GluN2A and GluN2B subunits to increased pre- and postsynaptic NMDAR activity and the mechanism underlying increased GluN2A-mediated NMDAR activity of PVN presympathetic neurons in SHRs. Our findings indicate that GluN2A, but not GluN2B, mediates the increased presynaptic and postsynaptic NMDAR activity and the firing activity of PVN neurons in SHRs. the protein kinase CK2 plays an essential role in the increased GluN2B Ser1480 phosphorylation level and GluN2A-mediated synaptic NMDAR activity of PVN neurons in SHRs. the protein kinase CK2 plays an essential role in the increased GluN2B Ser1480 phosphorylation level and GluN2A-mediated synaptic NMDAR activity of PVN neurons in SHRs This new information is important for our understanding of the molecular mechanisms involved in synaptic plasticity of the hypothalamus and in the development of hypertension

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION