Multiple neurotoxic stresses converge on MDMX proteolysis to cause neuronal apoptosis

Abstract

MDMX has been shown to modulate p53 in dividing cells after DNA damage. In this study, we investigated the role of MDMX in primary cultures of neurons undergoing cell death. We found that DNA damage, but also membrane-initiated apoptotic stresses (glutamate receptor; Amyloid b precursor) or survival factor deprivation downregulated MDMX protein levels. Forced downregulation of murine double minute X (MDMX) by shRNA induced apoptosis suggesting that MDMX is required for survival in neurons. Protease inhibitors prevented the loss of MDMX after neurotoxic treatments, indicating a regulation of protein stability. Some, but not all, neurotoxic stresses induced phosphorylation of MDMX at serine 367, further supporting regulation at the protein level. Interestingly, we found that depending on the stimulus either p53 or E2F1 was induced, but overexpression of MDMX inhibited the transcriptional activity of both proapoptotic factors, and maintained neuronal viability upon neurotoxic stresses. Taken together, our data show that MDMX is an antiapoptotic factor in neurons, whose degradation is induced by various stresses and allows activation of p53 and E2F-1 during neuronal apoptosis.

A Ruthenium-Containing Organometallic Compound Reduces Tumor Growth through Induction of the Endoplasmic Reticulum Stress GeneCHOP

“…Starting quantities of genes of interest were reported to those of a housekeeping gene (18S). Specificity of the amplification was controlled by a melting curve (31). Primer sequences are shown in Supplementary Materials and Methods.…”

“…Cells were maintained in DMEM with 10% fetal bovine serum and incubated in the presence of 5% CO 2 /95% air at 37jC. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tests were done with cells cultured in 96-well culture dishes (Costar) as previously described (31). Hypodiploid DNA was measured as described (32) using propidium iodide.…”

“…Cells were treated in triplicates, lysed, and Western blots were done as described (31). Equal loading was verified with an actin antibody (1/200; Dr. Aunis, Physiopathologic du Systeme nerveux, INSERM U575, Strasbourg, France).…”

“…Luciferase assays were done as described (31). Luciferase activity was measured by a luminometer (Berthold systems).…”

Regulation of a Notch3-Hes1 Pathway and Protective Effect by a Tocopherol-Omega Alkanol Chain Derivative in Muscle Atrophy

“…At the cellular level, production of ROS induces lipid peroxidation, protein oxidation, DNA damage, and mitochondrial dysfunctions. These cellular alterations activate specific signaling pathways, such as the unfolded protein response, and/or transcription factors, such as p53/p73, which in turn lead to cell death and tissue degeneration (Gonzalez de Aguilar et al, 2000;Benosman et al, 2007Benosman et al, , 2011Barbieri and Sestili, 2012).…”