ERK Integrates PKA and PKC Signaling in Superficial Dorsal Horn Neurons. I. Modulation of A-Type K+ Currents

2003 ◽  
Vol 90 (3) ◽  
pp. 1671-1679 ◽  
Author(s):  
Hui-Juan Hu ◽  
Kathi S. Glauner ◽  
Robert W. Gereau
Keyword(s):  
Protein Kinase ◽  
Dorsal Horn ◽  
Neuronal Excitability ◽  
Potassium Currents ◽  
Superficial Dorsal Horn ◽  
Dorsal Horn Neurons ◽  
Kinase C ◽  
Extracellular Signal ◽  
Whole Cell Recordings ◽  
K Currents

The transient outward potassium currents (also known as A-type currents or IA) are important determinants of neuronal excitability. In the brain, IA is modulated by protein kinase C (PKC), protein kinase A (PKA), and extracellular signal-related kinase (ERK), three kinases that have been shown to be critical modulators of nociception. We wanted to determine the effects of these kinases on IA in superficial dorsal horn neurons. Using whole cell recordings from cultured mouse spinal cord superficial dorsal horn neurons, we found that PKC and PKA both inhibit IA in these cells, and that PKC has a tonic inhibitory action on IA. Further, we provide evidence supporting the hypothesis that PKC and PKA do not modulate IA directly, but rather act as upstream activators of ERKs, which modulate IA. These results suggest that ERKs serve as signal integrators in modulation of IA in dorsal horn neurons and that modulation of A-type potassium currents may underlie aspects of central sensitization mediated by PKC, PKA, and ERKs.

Activation of extracellular signal-regulated protein kinase in dorsal horn neurons in the rat neuropathic intermittent claudication model

Pain ◽  
2004 ◽  
Vol 109 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Yi Liu ◽  
Koichi Obata ◽  
Hiroki Yamanaka ◽  
Yi Dai ◽  
Tetsuo Fukuoka ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Dorsal Horn ◽  
Intermittent Claudication ◽  
Dorsal Horn Neurons ◽  
Extracellular Signal

ERK Integrates PKA and PKC Signaling in Superficial Dorsal Horn Neurons. II. Modulation of Neuronal Excitability

2003 ◽  
Vol 90 (3) ◽  
pp. 1680-1688 ◽  
Author(s):  
Hui-Juan Hu ◽  
Robert W. Gereau
Keyword(s):  
Protein Kinase ◽  
Action Potential ◽  
Dorsal Horn ◽  
Spinal Cord Dorsal Horn ◽  
Erk Signaling ◽  
Membrane Properties ◽  
Superficial Dorsal Horn ◽  
Action Potential Firing ◽  
Dorsal Horn Neurons ◽  
Potential Firing

Protein kinases belonging to the protein kinase A (PKA), protein kinase C (PKC), and extracellular signal-related kinase (ERK) families have been identified as key players in modulating nociception at the level of the spinal cord dorsal horn, yet little is known about the effects of these kinases on membrane properties of the dorsal horn neurons. PKA, PKC, and ERK exert inhibitory effects on transient potassium currents (A-type currents or IA) in mouse superficial dorsal horn neurons ( Hu et al. 2003 ). Here we aimed to determine the effects of these kinases on action potential firing and membrane properties of these neurons to evaluate the impact of the modulation of IA (and other conductances) in these neurons. We found that activating PKC and PKA has dramatic effects on action potential firing, reflecting an increase in the excitability of superficial dorsal horn neurons. In addition, we found that inhibitors of both PKC and ERK signaling decrease the excitability of dorsal horn neurons, suggesting that these kinases exert a tonic excitation of these cells. Consistent with our findings that these kinases inhibit A-type currents, we found that PKA, PKC, and ERK act to shorten the first-spike latency after depolarization induced by current injection. In addition, activation of these kinases increases spike frequency and action potential amplitude of dorsal horn neurons. Interestingly, we found that the effects of PKA and PKC activators are blocked by inhibitors of ERK signaling, suggesting that PKA and PKC may exert their actions by activation of ERKs.

Activation of Protein Kinase C Increases Neuronal Excitability by Regulating Persistent Na+ Current in Mouse Neocortical Slices

1998 ◽  
Vol 80 (3) ◽  
pp. 1547-1551 ◽  
Author(s):  
Nadav Astman ◽  
Michael J. Gutnick ◽  
Ilya A. Fleidervish
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Action Potential ◽  
Neuronal Excitability ◽  
Specific Protein ◽  
Protein Kinase C Inhibitors ◽  
Cationic Current ◽  
Kinase C ◽  
Layer V ◽  
Neuronal Functions

Astman, Nadav, Michael J. Gutnick, and Ilya A. Fleidervish. Activation of protein kinase C increases neuronal excitability by regulating persistent Na+ current in mouse neocortical slices. J. Neurophysiol. 80: 1547–1551, 1998. Effects of the protein kinase C activating phorbol ester, phorbol 12-myristate 13-acetate (PMA), were studied in whole cell recordings from layer V neurons in slices of mouse somatosensory neocortex. PMA was applied intracellularly (100 nM to 1 μM) to restrict its action to the cell under study. In current-clamp recordings, it enhanced neuronal excitability by inducing a 10- to 20-mV decrease in voltage threshold for action-potential generation. Because spike threshold in neocortical neurons critically depends on the properties of persistent Na+ current ( I NaP), effects of PMA on this current were studied in voltage clamp. After blocking K+ and Ca2+ currents, I NaP was revealed by applying slow depolarizing voltage ramps from −70 to 0 mV. Intracellular PMA induced a decrease in I NaP at very depolarized membrane potentials. It also shifted activation of I NaP in the hyperpolarizing direction, however, such that there was a significant increase in persistent inward current at potentials more negative than −45 mV. When tetrodotoxin (TTX) was added to the bath, blocking I NaP and leaving only an outward nonspecific cationic current ( I cat), PMA had no apparent effect on responses to voltage ramps. Thus PMA did not affect I cat, and it did not induce any additional current. Intracellular application of the inactive PMA analogue, 4α-PMA, did not affect I NaP. The specific protein kinase C inhibitors, chelerythrine (20 μM) and calphostin C (10 μM), blocked the effect of PMA on I NaP. The data suggest that PMA enhances neuronal excitability via a protein kinase C–mediated increase in I NaP at functionally critical subthreshold voltages. This novel effect would modulate all neuronal functions that are influenced by I NaP, including synaptic integration and active backpropagation of action potential from the soma into the dendrites.

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