title: Induction and modulation of cerebellar granule neuron death by E2F-1.
abstract: Growing evidence suggests that certain cell cycle regulators also mediate neuronal death. Of relevance, cyclin D1-associated kinase activity is increased and the retinoblastoma protein (Rb), a substrate of the cyclin D1-Cdk4/6 complex, is phosphorylated during K(+) deprivation-evoked death of cerebellar granule neurons (CGNs). Cyclin-dependent kinase (CDK) inhibitors block this death, suggesting a requirement for the cyclin D1/Cdk4/6-Rb pathway. However, the downstream target(s) of this pathway are not well defined. The transcription factor E2F-1 is regulated by Rb and is reported to evoke death in proliferating cells when overexpressed. Accordingly, we examined whether E2F-1 was sufficient to evoke death of CGNs and whether it was required for death evoked by low K(+). We show that adenovirus-mediated expression of E2F-1 in CGNs results in apoptotic death, which is independent of p53, dependent upon Bax, and associated with caspase 3-like activity. In addition, we demonstrate that levels of E2F-1 mRNA and protein increase during K(+) deprivation-evoked death. The increase in E2F-1 protein is blocked by the CDK inhibitor flavopiridol. Finally, E2F-1-deficient neurons are modestly resistant to death induced by low K(+). These results indicate that E2F-1 expression is sufficient to promote neuronal apoptosis and that endogenous E2F-1 modulates the death of CGNs evoked by low K(+).
authors.affiliation: Neuroscience Research Institute, University of Ottawa, Ontario, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: O'Hare
authors.forename: S T
authors.initials: ST
authors.lastname: Hou
authors.forename: E J
authors.initials: EJ
authors.lastname: Morris
authors.forename: S P
authors.initials: SP
authors.lastname: Cregan
authors.forename: Q
authors.initials: Q
authors.lastname: Xu
authors.forename: R S
authors.initials: RS
authors.lastname: Slack
authors.forename: D S
authors.initials: DS
authors.lastname: Park
mesh_terms: D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002352:Carrier Proteins; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins; D016923:Cell Death; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors; D005419:Flavonoids / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D007763:Lac Operon; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: C533431:Arid4a protein, mouse; C494827:Bax protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493754:E2f1 protein, mouse; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010880:Piperidines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D019938:Cyclin D1; C077990:alvocidib; D001616:beta-Galactosidase; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D011188:Potassium