Regulation ofN-Methyl-d-Aspartate Receptor Function by Constitutively Active Protein Kinase C

Abstract

The ability of the constitutively active fragment of protein kinase C (PKM) to modulate N-methyl-D-aspartate (NMDA)-activated currents in cultured mouse hippocampal neurons and acutely isolated CA1 hippocampal neurons from postnatal rats was studied using patch-clamp techniques. The responses of two heterodimeric combinations of recombinant NMDA receptors (NR1a/NR2A and NR1a/NR2B) expressed in human embryonic kidney 293 cells were also examined. Intracellular applications of PKM potentiated NMDA-evoked currents in cultured and isolated CA1 hippocampal neurons. This potentiation was observed in the absence or presence of extracellular Ca2+ and was prevented by the coapplication of the inhibitory peptide protein kinase inhibitor(19-36). Furthermore, the PKM-induced potentiation was not a consequence of a reduction in the sensitivity of the currents to voltage-dependent blockade by extracellular Mg2+. We also found different sensitivities of the responses of recombinant NMDA receptors to the intracellular application of PKM. Some potentiation was observed with the NR1a/NR2A subunits, but none was observed with the NR1a/NR2B combination. Applications of PKM to inside-out patches taken from cultured neurons increased the probability of channel opening without changing single-channel current amplitudes or channel open times. Thus, the activation of protein kinase C is associated with potentiation of NMDA receptor function in hippocampal neurons largely through an increase in the probability of channel opening.

Subunit-Dependent High-Affinity Zinc Inhibition of Acid-Sensing Ion Channels

“…During each experiment, a voltage step of Ϫ10 mV from the holding potential was applied periodically to monitor the cell capacitance and access resistance. Recordings in which the access resistance or the capacitances changed by Ͼ10% during the experiment were not included in data analysis (Xiong et al, 1998). Solutions and chemicals.…”

ASIC1a-Specific Modulation of Acid-Sensing Ion Channels in Mouse Cortical Neurons by Redox Reagents

“…During each experiment, a voltage step of Ϫ10 mV from the holding potential was applied periodically to monitor cell capacitance and access resistance. Recordings in which access resistance or capacitance changed by Ͼ10% during the experiment were excluded for data analysis (Xiong et al, 1998;Chu et al, 2004b).…”

“…To address this concern, we also studied the effect of redox reagents on the ASIC current recorded in acutely isolated cortical neurons from adult mice. Neurons were isolated from 4-week-old mice, as described previously (Xiong et al, 1998). Similar to the cultured neurons, perfusion of 1.0 mM DTT increased the amplitude of the ASIC current (from Ϫ233.1 Ϯ 52.9 to Ϫ347.9 Ϯ 77.6 pA; n ϭ 7; p Ͻ 0.01), whereas 0.5 mM DTNB inhibited the current (from Ϫ376.3 Ϯ 51.8 to Ϫ265.9 Ϯ 44.4 pA; n ϭ 7; p Ͻ 0.05) (data not shown).…”

Direct Effects of Calmodulin on NMDA Receptor Single-Channel Gating in Rat Hippocampal Granule Cells

“…Several calcium-dependent proteins associated with the postsynaptic density alter NMDA receptor activity, including calmodulin (CaM) (Ehlers et al, 1996;Hisatsune et al, 1997, Rafiki et al, 1997Zhang et al, 1998;Krupp et al, 1999), calcineurin (Lieberman and Mody, 1994;Tong and Jahr, 1994;Tong et al, 1995), protein kinase C (PKC) (Chen and Huang, 1992;Wagner and Leonard, 1996;Xiong et al, 1998;Lu et al, 2000;Lan et al, 2001), and ␣-actinin-2 (Wyszynski et al, 1997;Zhang et al, 1998;Krupp et al, 1999). Therefore, it is generally acknowledged that calcium influx, in part through the NMDA channel, can regulate NMDA receptor activity via various pathways.…”