Sigma-1 receptors regulate Bcl-2 expression by reactive oxygen species-dependent transcriptional regulation of nuclear factor kappaB.
The expression of Bcl-2, the major antiapoptotic member of the Bcl-2 family, is under complex controls of several factors, including reactive oxygen species (ROS). The sigma-1 receptor (Sig-1R), which was recently identified as a novel molecular chaperone at the mitochondria-associated endoplasmic reticulum membrane (MAM), has been shown to exert robust cellular protective actions. However, mechanisms underlying the antiapoptotic action of the Sig-1R remain to be clarified. Here, we found that the Sig-1R promotes cellular survival by regulating the Bcl-2 expression in Chinese hamster ovary cells. Although both Sig-1Rs and Bcl-2 are highly enriched at the MAM, Sig-1Rs neither associate physically with Bcl-2 nor regulate stability of Bcl-2 proteins. However, Sig-1Rs tonically regulate the expression of Bcl-2 proteins. Knockdown of Sig-1Rs down-regulates whereas overexpression of Sig-1Rs up-regulates bcl-2 mRNA, indicating that the Sig-1R transcriptionally regulates the expression of Bcl-2. The effect of Sig-1R small interfering RNA down-regulating Bcl-2 was blocked by ROS scavengers and by the inhibitor of the ROS-inducible transcription factor nuclear factor kappaB (NF-kappaB). Knockdown of Sig-1Rs up-regulates p105, the precursor of NF-kappaB, while concomitantly decreasing inhibitor of nuclear factor-kappaBalpha. Sig-1R knockdown also accelerates the conversion of p105 to the active form p50. Lastly, we showed that knockdown of Sig-1Rs potentiates H(2)O(2)-induced apoptosis; the action is blocked by either the NF-kappaB inhibitor oridonin or overexpression of Bcl-2. Thus, these findings suggest that Sig-1Rs promote cell survival, at least in part, by transcriptionally regulating Bcl-2 expression via the ROS/NF-kappaB pathway.
Cellular Pathobiology Section, Cellular Neurobiology Research Branch, IRP, NIDA, National Institutes of Health, DHHS, Triad Technology Building, Baltimore, MD, USA.
Johann
J
Meunier
Teruo
T
Hayashi
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D045786:Diterpenes, Kaurane / Q000494:pharmacology; D015536:Down-Regulation; D018832:Molecular Chaperones / Q000378:metabolism; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000494:pharmacology*; D017480:Receptors, sigma / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation; D000097605:Sigma-1 Receptor
D045786:Diterpenes, Kaurane; D018832:Molecular Chaperones; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D017480:Receptors, sigma; D000097605:Sigma-1 Receptor; C011959:oridonin