title: c-Rel deficiency increases caspase-4 expression and leads to ER stress and necrosis in EBV-transformed cells.
abstract: 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.
authors: Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, United States of America.
authors: Aníbal
authors: A
authors: Valentín-Acevedo
authors: Frank L
authors: FL
authors: Sinquett
authors: Lori R
authors: LR
authors: Covey
mesh_terms: D001343:Autophagy / Q000235:genetics; D019013:CD40 Antigens / Q000378:metabolism; D053471:Caspases, Initiator / Q000235:genetics / Q000378:metabolism*; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D048430:Cell Shape; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000473:pathology / Q000648:ultrastructure; D059865:Endoplasmic Reticulum Stress / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D009336:Necrosis / Q000201:enzymology* / Q000473:pathology*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000172:deficiency* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics; D014763:Viral Matrix Proteins / Q000378:metabolism
chemical_list: D019013:CD40 Antigens; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D016271:Proto-Oncogene Proteins c-myc; D020569:Proto-Oncogene Proteins c-rel; D014763:Viral Matrix Proteins; C093516:CASP4 protein, human; D053471:Caspases, Initiator