title: Podophyllotoxin induces CREB phosphorylation and CRE-driven gene expression via PKA but not MAPKs.
abstract: CRE-driven luciferase reporter is commonly used in drug screening systems involving G protein-coupled receptors (GPCRs). In a screen campaign designed to search for melanocortin-4 receptor (MC4R) agonists, podophyllotoxin, a microtubules disruptor, was found to induce cAMP-responsive element (CRE)-driven reporter expression. MC4R was not involved because podophyllotoxin induced CREB activation and CRE-driven transcription in cells not expressing MC4R. Previous studies indicated that intracellular calcium, PKA, and MAPKs are involved in CREB phosphorylation and activation. Our studies revealed that podophyllotoxin did not affect intracellular calcium level and the phosphorylation state of p38. Podophyllotoxin induced JNK and ERK activation, but blockade of JNK and ERK activation with specific inhibitors had no effect on podophyllotoxin-induced CREB activation and CRE-regulated gene expression. Further experiments revealed that H89, a specific inhibitor of PKA, significantly inhibited podophyllotoxin-induced CREB activation. Podophyllotoxin itself did not alter intracellular cAMP level. Taken together, podophyllotoxin induces CREB activation and CRE-driven gene expression via PKA activation by a cAMP-independent mechanism.
authors.affiliation: State Key Laboratory of Drug Research, National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
authors.forename: Ya Qiong
authors.initials: YQ
authors.lastname: Chen
authors.forename: Xin
authors.initials: X
authors.lastname: Xie
mesh_terms: D000818:Animals; D019556:COS Cells; D020013:Calcium Signaling / Q000187:drug effects; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000096:biosynthesis* / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D017930:Genes, Reporter; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D011034:Podophyllotoxin / Q000494:pharmacology*; D044105:Receptor, Melanocortin, Type 4 / Q000819:agonists*; D020218:Response Elements / Q000235:genetics; D013449:Sulfonamides / Q000494:pharmacology; D015533:Transcriptional Activation / Q000187:drug effects; D050257:Tubulin Modulators / Q000494:pharmacology*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D007546:Isoquinolines; D044105:Receptor, Melanocortin, Type 4; D013449:Sulfonamides; D050257:Tubulin Modulators; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D011034:Podophyllotoxin; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide