Signaling pathways from membrane lipid rafts to JNK1 activation in reactive nitrogen species-induced non-apoptotic cell death

Abstract

At present, the signaling pathways controlling reactive nitrogen species (RNS)-induced non-apoptotic cell death are relatively less understood. In this work, various RNS donors are found to induce caspase-independent non-apoptotic cell death in mouse embryonic fibroblasts (MEF). In search of the molecular mechanisms, we first established the role of c-Jun N-terminal kinase (JNK) in RNS-induced non-apoptotic cell death. RNS readily activate JNK, and the jnk1À/À MEF are resistant to RNS-induced cell death. Moreover, the reconstitution of JNK1 effectively restores the sensitivity to RNS. Next, we identified tumor necrosis factor receptor-associated factor 2 (TRAF2) and apoptosis signal-regulating kinase 1 (ASK1) as the essential upstream molecules for RNS-induced JNK activation and cell death. RNS fail to activate JNK and induce cell death in traf2À/À MEF; and reconstitution of TRAF2 effectively restores the responsiveness of traf2À/À MEF to RNS. Moreover, RNS-induced ASK1 activation is impaired in traf2À/À cells and overexpression of a mutant ASK1 protein suppresses RNS-induced cell death in wild-type MEF cells. Last, we explored the signaling events upstream of TRAF2 and found that translocation of TRAF2 and JNK1 onto membrane lipid rafts is required for RNS-mediated JNK1 activation and cell death. Taken together, data from our study reveal a novel signaling pathway regulating RNS-induced JNK1 activation and non-apoptotic cell death.

A novel role for jun N-terminal Kinase signaling in olfactory sensory neuronal death

“…This group of MAPKs regulates transcription by binding and subsequently phosphorylating the transcription factor c-Jun (Johnson and Lapadat, 2002). JNK activity has been implicated in multiple forms of cell death, including apoptosis (Tournier et al, 2000) and necrosis (Wu et al, 2008), in response to many and varied stimuli. Here we show that the death of olfactory sensory neurons is mediated by JNK signaling; JNK inhibitors prolong the survival of OSNs in vitro (Fig 4) and in vivo (Fig 7), and JNK signaling is high following induction of olfactory sensory neuronal death in culture (Fig 5) or in vivo (Fig 6).…”

Autophagy plays a protective role during zVAD-induced necrotic cell death

“…In this study, several approaches were used to detect cell death quantitatively and qualitatively, including (i) morphological changes under phase-contrast microscopy, (ii) Hoechstsytox staining as described previously, 21 (iii) the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test as described elsewhere, 22 and (iv) the propidium iodide (PI) exclusion assay using flow cytometry. 23 Briefly, after designated treatments, cells were collected and resuspended in PBS containing PI (2 μg/ml) for incubation at 37°C for 10 min.…”

Critical role of SCD1 in autophagy regulation via lipogenesis and lipid rafts-coupled AKT-FOXO1 signaling pathway

“…61 Cells were lysed in TNE buffer containing 150 mM NaCl, 1.0% Triton X-100, 3 mM EDTA, 20 mM TRIS-HCl (pH 7.5) with a phosphatase and protease inhibitor mixture. The cells were then homogenized by passage through a 23-gauge needle 10 times and incubated for 1 h on ice.…”