c-Rel deficiency increases caspase-4 expression and leads to ER stress and necrosis in EBV-transformed cells

• Published in: PloS one Vol. 6; no. 10; p. e25467
• Main Authors: Valentín-Acevedo, Aníbal, Sinquett, Frank L, Covey, Lori R
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 03.10.2011; Public Library of Science (PLoS)
• Subjects: Antigens; Apoptosis; Autophagy; Autophagy - genetics; B cells; Biology; c-Myc protein; Caspase; Caspase-4; Caspases, Initiator - genetics; Caspases, Initiator - metabolism; CD40 Antigens - metabolism; Cell death; Cell Line, Transformed; Cell Proliferation; Cell Shape; Cell survival; Cytotoxicity; Defects; Endoplasmic reticulum; Endoplasmic Reticulum - genetics; Endoplasmic Reticulum - pathology; Endoplasmic Reticulum - ultrastructure; Endoplasmic Reticulum Stress - genetics; Fibroblasts; Gene amplification; Gene expression; Gene Expression Profiling; Gene Expression Regulation; Genes; Hemopoiesis; Herpesvirus 4, Human - physiology; Homeostasis; Humans; Immunoglobulin M; Inflammation; Job's syndrome; Kinases; Lymphoblastoid cell lines; Lymphoma; Mortality; Myc protein; Necrosis; Necrosis - enzymology; Necrosis - pathology; Neurosciences; NF- Kappa B protein; NF-κB protein; Phagocytosis; Proteins; Proto-Oncogene Proteins c-myc - metabolism; Proto-Oncogene Proteins c-rel - deficiency; Proto-Oncogene Proteins c-rel - metabolism; Signal transduction; Signal Transduction - genetics; siRNA; Stress; Stress (Physiology); Stress, Physiological - genetics; Stresses; Survival; Target recognition; Transformed cells; Tumorigenesis; Viability; Viral Matrix Proteins - metabolism; United States > US; New Jersey
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0025467

LMP1-mediated activation of nuclear factor of kappaB (NF-κB) is critical for the ligand independent proliferation and cell survival of in vitro EBV-transformed lymphoblastoid cell lines (LCLs). Previous experiments revealed that a majority of LMP1-dependent responses are regulated by NF-κB. However, the extent that individual NF-κB family members are required for these responses, in particular, c-Rel, whose expression is restricted to mature hematopoietic cells, remains unclear. Here we report that low c-Rel expression in LCLs derived from a patient with hyper-IgM syndrome (Pt1), resulted in defects in proliferation and cell survival. In contrast to studies that associated loss of NF-κB with increased apoptosis, Pt1 LCLs failed to initiate apoptosis and alternatively underwent autophagy and necrotic cell death. Whereas the proliferation defect appeared linked to a c-Rel-associated decrease in c-myc expression, identified pro-survival and pro-apoptotic targets were expressed at or near control levels consistent with the absence of apoptosis. Ultrastructural examination of Pt1 LCLs revealed a high level of cellular and ER stress that was further supported by gene expression profiling showing the upregulation of several genes involved in stress and inflammation. Apoptosis-independent cell death was accompanied by increased expression of the inflammatory marker, caspase-4. Using gene overexpression and siRNA knockdown we demonstrated that levels of c-Rel directly modulated expression of caspase-4 as well as other ER stress genes. Overall, these findings reveal the importance of c-Rel in maintaining LCL viability and that decreased expression results in ER stress and a default response leading to necrotic cell death.