Impairment of nuclear factor-kappaB activation increased glutamate excitotoxicity in a motoneuron-neuroblastoma hybrid cell line expressing mutant (G93A) Cu/Zn-superoxide dismutase.
Mutations in the superoxide dismutase 1 (SOD1) gene are linked to glutamate excitotoxicity in familial amyotrophic lateral sclerosis (fALS), but the underlying mechanism remains unclear. We investigated whether nuclear factor-kappaB (NF-kappaB) activation is involved in glutamate excitotoxicity by using motor neuron-neuroblastoma hybrid cells that expressed a mutant (G93A) SOD1 (mtSOD1) or wild-type SOD1 (wtSOD1). MtSOD1 cells were more vulnerable to glutamate excitotoxicity than wtSOD1 cells and showed higher NF-kappaB activity, higher nuclear cRel expression, and lower nuclear RelA expression under basal conditions. Glutamate treatment increased NF-kappaB activation along with nuclear expressions of RelA and cRel in wtSOD1 cells but induced only weak nuclear RelA expression in mtSOD1 cells. Suppression of NF-kappaB activation using transfection of the superrepressive mutant form of IkappaBalpha (mIkappaBalpha) inhibited nuclear RelA expression in both types of SOD1 cells, which increased glutamate excitotoxicity in wtSOD1 cells but not in mtSOD1 cells. Furthermore, immunohistochemistry confirmed stronger RelA immunoreactivity in the nuclei of motor neurons of spinal cord in wild-type SOD1 transgenic mice than in those in SOD1 G93A transgenic mice. In addition, we found that glutamate treatment decreased XIAP expression and increased caspase-3 activity in mtSOD1 cells and mIkappaBalpha-overexpressing wtSOD1 cells. Our results suggest that glutamate excitotoxicity in motor neurons of SOD1-linked fALS is attributable, at least in part, to the impairment of IkappaBalpha-dependent RelA activation and subsequent apoptosis mediated by XIAP inhibition and caspase-3 activation.
Pyo
Jung-Soo
JS
Department of Anatomy and Neurosciences, Eulji University School of Medicine, Daejon, South Korea.
Ko
Young San
YS
Kim
Woo Ho
WH
Kim
Manho
M
Lee
Kwang-Woo
KW
Nam
Seon Young
SY
Chung
Hee-Yong
HY
Cho
Sung Jin
SJ
Baik
Tai-Kyoung
TK
Lee
Byung Lan
BL
D000818:Animals; D001711:Biotransformation / Q000502:physiology; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism; D005456:Fluorescent Dyes; D005822:Genetic Vectors; D018698:Glutamic Acid / Q000633:toxicity*; D006801:Humans; D006822:Hybrid Cells; D007150:Immunohistochemistry; D007211:Indoles; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism*; D009154:Mutation / Q000235:genetics / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism; D017470:Receptors, Glutamate / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism*
D005456:Fluorescent Dyes; D007211:Indoles; D016328:NF-kappa B; D017470:Receptors, Glutamate; D018698:Glutamic Acid; C007293:DAPI; D008156:Luciferases; D013482:Superoxide Dismutase; D053148:Caspase 3