Endoplasmic reticulum stress is accompanied by activation of NF-κB in amyotrophic lateral sclerosis

Background: Recent studies have indicated that endoplasmic reticulum (ER) stress is involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). ER stress occurs when the ER-mitochondria calcium cycle is disturbed and misfolded proteins accumulate in the ER. To cope with ER stress, cells activate the unfolded protein response (UPR). Accumulating evidence from non-neuronal cell models suggests that there is extensive cross-talk between the UPR and the NF-κB pathway. Methods: Here we investigated the expression of NF-κB and the main UPR markers X-box binding protein 1 (XBP1), basic leucine-zipper transcription factor 6 (ATF6) and phosphorylated eukaryotic initiation factor-2α (p-eIF2) in mutated SOD1^G93A cell models of ALS, as well as their modulation by lipopolysaccharide and ER-stressing (tunicamycin) stimuli. Results: Expression of NF-κB was enhanced in the presence of SOD1^G93A. Lipopolysaccharide did not induce the UPR in NSC34 cells and motor neurons in a mixed motor neuron-glia coculture system. The induction of the UPR by tunicamycin was accompanied by activation of NF-κB in NSC34 cells and motor neurons. Conclusion: Our data linked two important pathogenic mechanisms of ALS, ER stress and NF-κB signalling, in motor neurons.