Okadaic acid inhibits the trichostatin A-mediated increase of human CYP46A1 neuronal expression in a ERK1/2-Sp3-dependent pathway.
The CYP46A1 gene codes for the cholesterol 24-hydroxylase, a cytochrome P450 specifically expressed in neurons and responsible for the majority of cholesterol turnover in the central nervous system. Previously, we have demonstrated the critical participation of Sp transcription factors in the CYP46A1 response to histone deacetylase (HDAC) inhibitors, and in this study we investigated the involvement of intracellular signaling pathways in the trichostatin A (TSA) effect. Our results show that pretreatment of neuroblastoma cells with chemical inhibitors of mitogen-activated kinase kinase (MEK)1 significantly potentiates the TSA-dependent induction of cholesterol 24-hydroxylase, whereas inhibition of protein phosphatases by okadaic acid (OA) or overexpression of MEK1 partially impairs the TSA effect without affecting histone hyperacetylation at the promoter. Immunoblotting revealed that TSA treatment decreases ERK1/2 phosphorylation concomitantly with a decrease in Sp3 binding activity, which are both reversed by pretreatment with OA. Chromatin immunoprecipitation analysis demonstrated that TSA induces the release of p-ERK1/2 from the CYP46A1 proximal promoter, whereas pretreatment with OA restores the co-occupancy of Sp3-ERK1/2 in the same promoter fragments. We demonstrate for the first time the participation of MEK-ERK1/2 signaling pathway in HDAC inhibitor-dependent induction of cytochrome P450 gene expression, underlying the importance of this regulatory signaling mechanism in the control of brain cholesterol elimination.
Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL),  University of Lisbon, 1649-019 Lisbon,  Portugal.
Maria João
MJ
Nunes
Miguel
M
Moutinho
Inês
I
Milagre
Maria João
MJ
Gama
Elsa
E
Rodrigues
D001921:Brain / Q000166:cytology; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism; D000072556:Cholesterol 24-Hydroxylase; D004790:Enzyme Induction / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D006877:Hydroxamic Acids / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology*; D009928:Organ Specificity; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D051705:Sp3 Transcription Factor / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000096:biosynthesis / Q000235:genetics*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects
D006877:Hydroxamic Acids; D010750:Phosphoproteins; C497121:SP3 protein, human; D051705:Sp3 Transcription Factor; D019319:Okadaic Acid; C012589:trichostatin A; D002784:Cholesterol; D013250:Steroid Hydroxylases; D000072556:Cholesterol 24-Hydroxylase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1