title: Deregulated Cdk5 promotes oxidative stress and mitochondrial dysfunction.
abstract: Oxidative stress is one of the earliest events in Alzheimer's disease (AD). A chemical genetic screen revealed that deregulated cyclin-dependent kinase 5 (Cdk5) may cause oxidative stress by compromising the cellular anti-oxidant defense system. Using novel Cdk5 modulators, we show the mechanism by which Cdk5 can induce oxidative stress in the disease's early stage and cell death in the late stage. Cdk5 dysregulation upon neurotoxic insults results in reactive oxygen species (ROS) accumulation in neuronal cells because of the inactivation of peroxiredoxin I and II. Sole temporal activation of Cdk5 also increases ROS, suggesting its major role in this process. Cdk5 inhibition rescues mitochondrial damage upon neurotoxic insults, thereby revealing Cdk5 as an upstream regulator of mitochondrial dysfunction. As mitochondrial damage results in elevated ROS and Ca(2+) levels, both of which activate Cdk5, we propose that a feedback loop occurs in late stage of AD and leads to cell death (active Cdk5 --> ROS --> excess ROS --> mitochondrial damage --> ROS --> hyperactive Cdk5 --> severe oxidative stress and cell injury --> cell death). Cdk5 inhibition upon neurotoxic insult prevents cell death significantly, supporting this hypothesis. As oxidative stress and mitochondrial dysfunction play pivotal roles in promoting neurodegeneration, Cdk5 could be a viable therapeutic target for AD.
authors.affiliation: Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Kai-Hui
authors.initials: KH
authors.lastname: Sun
authors.forename: Yolanda
authors.initials: Y
authors.lastname: de Pablo
authors.forename: Fabien
authors.initials: F
authors.lastname: Vincent
authors.forename: Kavita
authors.initials: K
authors.lastname: Shah
mesh_terms: D000544:Alzheimer Disease / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D051360:Cyclin-Dependent Kinase 5 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics*; D018816:Genes, cdc / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D009410:Nerve Degeneration / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D009474:Neurons / Q000378:metabolism*; D009498:Neurotoxins / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D016716:PC12 Cells; D054464:Peroxiredoxins / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D009498:Neurotoxins; D017382:Reactive Oxygen Species; D054464:Peroxiredoxins; D051360:Cyclin-Dependent Kinase 5