title: Involvement of the transcription factor E2F1/Rb in kainic acid-induced death of murine cerebellar granule cells.
abstract: The full mechanisms underlying neuronal death following excitotoxic insult remain unclear, despite many in vivo and in vitro studies. Recent work has focused on various signaling molecules and pathways, normally strictly regulated, that can trigger death if perturbed. The transcription factor, E2F1 is pivotal in controlling cell death under stress situations. The current study aimed to investigate the role of this transcription factor in modulating neuronal death following kainic acid (KA) treatment of cultured mouse cerebellar granule cells (CGCs). KA-induced death of CGCs was attenuated by the selective KA/AMPA receptor antagonist CNQX, but not MK-801. Such neuronal death was caspase-3-independent and did not activate many known death genes, such as Fas receptor, caspase-8 and p38. However, hyperphosphorylation of Rb showed a transient increase which may lead to activation of E2F1. Indeed E2F1 +/+ and -/- CGCs showed a differential response to KA-mediated toxicity, in that E2F1 -/- neurons were significantly less susceptible to KA compared to E2F1 +/+ neurons, albeit both E2F1 +/+ and -/- neurons expressed similar levels of KA receptors and responded similarly to kainate antagonist, CNQX. Using selective inhibitors to CDKs, such as olomoucine, roscovitine and flavopiridol, and the inhibitor SB203580 to p38 MAPK, we ruled out the possibility that Rb inactivation through hyperphosphorylation was due to either upstream kinases. Therefore activation of Rb/E2F1 pathway appears to involve novel interactions yet to be elucidated.
authors.affiliation: Experimental Stroke Group, NRC Institute for Biological Sciences, National Research Council of Canada, Building M54, 1500 Montreal Road, Ottawa, ON K1A 0R6, Canada. r.a.smith@bio.gla.ac.uk
authors.forename: Robert A
authors.initials: RA
authors.lastname: Smith
authors.forename: Teena
authors.initials: T
authors.lastname: Walker
authors.forename: Xiaoqi
authors.initials: X
authors.lastname: Xie
authors.forename: Sheng T
authors.initials: ST
authors.lastname: Hou
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D016923:Cell Death / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D004268:DNA-Binding Proteins; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D007608:Kainic Acid / Q000633:toxicity*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D018092:Kainic Acid Receptors / Q000145:classification / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016291:Dizocilpine Maleate; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007608:Kainic Acid; D020930:MAP Kinase Kinase Kinases; D012333:RNA, Messenger; D018092:Kainic Acid Receptors; D016160:Retinoblastoma Protein; D014157:Transcription Factors; C493754:E2f1 protein, mouse