Altered phosphorylation and localization of the A-type channel, Kv4.2 in status epilepticus.
Extracelluar signal-regulated kinase (ERK) pathway activation has been demonstrated following convulsant stimulation; however, little is known about the molecular targets of ERK in seizure models. Recently, it has been shown that ERK phosphorylates Kv4.2 channels leading to down-regulation of channel function, and substantially alters dendritic excitability. In the kainate model of status epilepticus (SE), we investigated whether ERK phosphorylates Kv4.2 and whether the changes in Kv4.2 were evident at a synaptosomal level during SE. Western blotting was performed on rat hippocampal whole cell, membrane, synaptosomal, and surface biotinylated extracts following systemic kainate using an antibody generated against the Kv4.2 ERK sites and for Kv4.2, ERK, and phospho-ERK. ERK activation was associated with an increase in Kv4.2 phosphorylation during behavioral SE. During SE, ERK activation and Kv4.2 phosphorylation were evident at the whole cell and synaptosomal levels. In addition, while whole-cell preparations revealed no alterations in total Kv4.2 levels, a decrease in synaptosomal and surface expression of Kv4.2 was evident after prolonged SE. These results demonstrate ERK pathway coupling to Kv4.2 phosphorylation. The finding of decreased Kv4.2 levels in hippocampal synaptosomes and surface membranes suggest additional mechanisms for decreasing the dendritic A-current, which could lead to altered intrinsic membrane excitability during SE.
Lugo
Joaquin N
JN
The Cain Foundation Laboratories, Department of Pediatrics, Houston, Texas, USA.
Barnwell
Lyndon Forbes
LF
Ren
Yajun
Y
Lee
Wai Ling
WL
Johnston
Lisa Danielle
LD
Kim
Rebecca
R
Hrachovy
Richard A
RA
Sweatt
John David
JD
Anderson
Anne E
AE
D000818:Animals; D004569:Electroencephalography / Q000379:methods; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology; D008297:Male; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D051672:Shal Potassium Channels / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D013226:Status Epilepticus / Q000378:metabolism* / Q000503:physiopathology; D009435:Synaptic Transmission / Q000502:physiology; D013574:Synaptosomes / Q000378:metabolism / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
D051672:Shal Potassium Channels