title: Cyclin-dependent kinase 5 mediates neurotoxin-induced degradation of the transcription factor myocyte enhancer factor 2.
abstract: Regulation of the process of neuronal death plays a central role both during development of the CNS and in adult brain. The transcription factor myocyte enhancer factor 2 (MEF2) plays a critical role in neuronal survival. Cyclin-dependent kinase 5 (Cdk5) mediates neurotoxic effects by phosphorylating and inhibiting MEF2. How Cdk5-dependent phosphorylation reduces MEF2 transactivation activity remained unknown. Here, we demonstrate a novel mechanism by which Cdk5, in conjunction with caspase, inhibits MEF2. Using primary cerebellar granule neuron as a model, our investigation reveals that neurotoxicity induces destabilization of MEF2s in neurons. Destabilization of MEF2 is caused by an increase in caspase-dependent cleavage of MEF2. This cleavage event requires nuclear activation of Cdk5 activity. Phosphorylation by Cdk5 alone is sufficient to promote degradation of MEF2A and MEF2D by caspase-3. In contrast to MEF2A and MEF2D, MEF2C is not phosphorylated by Cdk5 after glutamate exposure and, therefore, resistant to neurotoxin-induced caspase-dependent degradation. Consistently, blocking Cdk5 or enhancing MEF2 reduced toxin-induced apoptosis. These findings define an important regulatory mechanism that for the first time links prodeath activities of Cdk5 and caspase. The convergence of Cdk5 phosphorylation-dependent caspase-mediated degradation of nuclear survival factors exemplified by MEF2 may represent a general process applicable to the regulation of other survival factors under diverse neurotoxic conditions.
authors.affiliation: Department of Medicine, Rhode Island Hospital and Brown Medical School, Providence, Rhode Island 02903, USA.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Tang
authors.forename: Xuemin
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Gong
authors.forename: Ming
authors.initials: M
authors.lastname: Tong
authors.forename: David
authors.initials: D
authors.lastname: Park
authors.forename: Zhengui
authors.initials: Z
authors.lastname: Xia
authors.forename: Zixu
authors.initials: Z
authors.lastname: Mao
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western / Q000379:methods; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002452:Cell Count / Q000379:methods; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D002843:Chromatin / Q000187:drug effects; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism*; D004347:Drug Interactions; D018698:Glutamic Acid / Q000633:toxicity*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008156:Luciferases; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009498:Neurotoxins / Q000633:toxicity*; D009842:Oligopeptides / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D000077546:Roscovitine; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014162:Transfection / Q000379:methods
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D002843:Chromatin; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D009498:Neurotoxins; D009842:Oligopeptides; D047428:Protein Kinase Inhibitors; D011687:Purines; D012333:RNA, Messenger; C090535:benzyloxycarbonyl-isoleucyl-glutamyl(O-tert-butyl)-alanyl-leucinal; C476093:z-Val-Ala-Asp(Ome)-fluoromethylketone; D000077546:Roscovitine; D049452:Green Fluorescent Proteins; D018698:Glutamic Acid; D008156:Luciferases; D051360:Cyclin-Dependent Kinase 5; D020169:Caspases