title: Gene expression changes associated with the endoplasmic reticulum stress response induced by microsomal cytochrome p450 overproduction.
abstract: Induction of drug-metabolizing microsomal cytochromes p450 (p450s) results in a striking proliferation of the smooth endoplasmic reticulum (ER). Overexpression of P450s in yeast and cultured cells produces a similar response. The signals mediating this process are not known but probably involve signal transduction pathways involved in the unfolded protein response (UPR) or the ER overload response (EOR). We have examined the temporal response of specific genes in these pathways and genes globally to overexpression of p450 in cultured cells. Activity of NFkappaB, an EOR component, was substantially increased by overexpression of full-length p450 2C2 or a chimera with the 28-amino acid signal anchor sequence of p450 2C2 in HepG2 cells, and the activation correlated temporally with the accumulation of p450 in the cells. In the UPR pathway, activation of the transcription factor XBP1 by IRE1 also correlated with the accumulation of p450 in the cells, and in contrast, maximum activation of the BiP/grp78 promoter preceded the accumulation. Differential effects of expression of p450 on apoptosis were observed in nonhepatic COS1 and hepatic HepG2 cells. In COS1 cells, apoptosis was induced, and this correlated with sustained activation of the pro-apoptotic JNK pathway, induction of CHOP, and an absence of the increased NFkappaB activity. In HepG2 cells, JNK was only transiently activated, and CHOP expression was not induced. As assessed by DNA microarray analysis, up-regulation of signaling genes was predominant including those involved in anti-apoptosis and ER stress. These results suggest that both the EOR and UPR pathways are involved in the cellular response to induction of p450 expression and that in hepatic cells genes are also induced to block apoptosis, which may be a physiologically relevant response to prevent cell death during xenobiotic induced expression of p450 in the liver.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Szczesna-Skorupa
authors.forename: Ci-Di
authors.initials: CD
authors.lastname: Chen
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Byron
authors.initials: B
authors.lastname: Kemper
mesh_terms: D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D019556:COS Cells; D006528:Carcinoma, Hepatocellular; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D015870:Gene Expression / Q000502:physiology; D006360:Heat-Shock Proteins; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008861:Microsomes / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D012326:RNA Splicing; D000071701:Regulatory Factor X Transcription Factors; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000071717:X-Box Binding Protein 1
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; C497249:DDIT3 protein, human; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D016328:NF-kappa B; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; D051742:Transcription Factor CHOP; D003577:Cytochrome P-450 Enzyme System; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases