Article

Cyclin-dependent kinase 5 is an upstream regulator of mitochondrial fission during neuronal apoptosis

Universitätsmedizin Göttingen, Göttingen, Lower Saxony, Germany
Cell Death and Differentiation (Impact Factor: 8.39). 05/2007; 14(4):651-61. DOI: 10.1038/sj.cdd.4402087
Source: PubMed

ABSTRACT Under physiological conditions, mitochondrial morphology dynamically shifts between a punctuate appearance and tubular networks. However, little is known about upstream signal transduction pathways that regulate mitochondrial morphology. We show that mitochondrial fission is a very early and kinetically invariant event during neuronal cell death, which causally contributes to cytochrome c release and neuronal apoptosis. Using a small molecule CDK5 inhibitor, as well as a dominant-negative CDK5 mutant and RNAi knockdown experiments, we identified CDK5 as an upstream signalling kinase that regulates mitochondrial fission during apoptosis of neurons. Vice versa, our study shows that mitochondrial fission is a modulator contributing to CDK5-mediated neurotoxicity. Thereby, we provide a link that allows integration of CDK5 into established neuronal apoptosis pathways.

Full-text

Available from: Gunnar P H Dietz, Mar 31, 2015
0 Bookmarks
 · 
85 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mitochondrial functions are essential for the survival and function of neurons. Recently, it has been demonstrated that mitochondrial functions are highly associated with mitochondrial morphology, which is dynamically changed by the balance between fusion and fission. Mitochondrial morphology is primarily controlled by the activation of dynamin-related proteins including dynamin-related protein 1 (Drp1), which promotes mitochondrial fission. Drp1 activity is regulated by several post-translational modifications, thereby modifying mitochondrial morphology. Here, we found that phosphorylation of Drp1 at serine 616 (S616) is mediated by cyclin-dependent kinase 5 (CDK5) in post-mitotic rat neurons. Perturbation of CDK5 activity modified the level of Drp1(S616) phosphorylation and mitochondrial morphology in neurons. In addition, phosphorylated Drp1(S616) preferentially localized as a cytosolic monomer compared with total Drp1. Furthermore, roscovitine, a chemical inhibitor of CDKs, increased oligomerization and mitochondrial translocation of Drp1, suggesting that CDK5-dependent phosphorylation of Drp1 serves to reduce Drp1's fission-promoting activity. Taken together, we propose that CDK5 has a significant role in the regulation of mitochondrial morphology via inhibitory phosphorylation of Drp1(S616) in post-mitotic neurons.
    Experimental and Molecular Medicine 07/2014; 46:e105. DOI:10.1038/emm.2014.36 · 2.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Over the last two decades, the identification of missense mutations in the α-synuclein (α-Syn) gene SNCA in families with inherited Parkinson's disease (PD) has reinforced the central role of α-Syn in PD pathogenesis. Recently, a new missense mutation (H50Q) in α-Syn was described in patients with a familial form of PD and dementia. Here we investigated the effects of this novel mutation on the biophysical properties of α-Syn and the consequences for its cellular function. We found that the H50Q mutation affected neither the structure of free or membrane-bound α-Syn monomer nor its interaction with metals or its capacity to be phosphorylated in vitro. However, compared to the wild-type protein, the H50Q mutation accelerated α-Syn fibrillization in vitro. In cell-based models, H50Q mutation did not affect neither α-Syn subcellular localization, nor its ability to be phosphorylated by PLK2 and GRK6. Interestingly, H50Q increased α-Syn secretion from SHSY5Y cells into culture medium and induced more mitochondrial fragmentation in hippocampal neurons. Toxicity analysis revealed that, while the transient overexpression of WT or H50Q did not induce toxicity, both species induced significant cell death when added to the culture medium of hippocampal neurons. Strikingly, H50Q exhibited more toxicity, suggesting that the H50Q-related enhancement of α-Syn aggregation and secretion may play a role in the extracellular toxicity of this mutant. Together, our results provide novel insight into the mechanism by which this newly described PD-associated mutation may contribute to the pathogenesis of PD and related disorders.
    Journal of Biological Chemistry 06/2014; 289(32). DOI:10.1074/jbc.M114.553297 · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Accumulating data suggests that mitochondrial deficits may underline both sporadic and familial Parkinson's disease (PD) neurodegenerative process. Impairment of mitochondrial dynamics results in reactive oxygen species (ROS) production, decreases mitochondrial membrane potential, and could potentiate the accumulation of dysfunctional mitochondria. Excessive mitochondrial fragmentation is associated with the pathology of sporadic PD. Therefore, we modulated mitochondria fusion and fission in different sporadic PD cellular models. We found alterations in two proteins known to regulate mitochondrial fusion and fission events (OPA1 and Drp1, respectively). OPA1 long isoform cleavage seems to be, at least in part, responsible for mitochondrial fragmented pattern observed in sporadic PD cellular models. Moreover, mitochondrial fragmentation can also occur due to an increase in Drp1 that is translocated into the mitochondria by phosphorylation. To disclose the relevance of these alterations to the fragmentation of the mitochondrial network, we overexpressed OPA1 and knock down Drp1. OPA1 overexpression did not rescue MPP(+)-induced increase in ROS. Nevertheless, Drp1 knockdown due to an increase in mitochondrial elongation and interconnectivity rescued mitochondrial membrane potential and decreased ROS production in sporadic PD cells. Overall, our findings suggest that Drp1-dependent mitochondrial fragmentation plays a crucial role in mediating mitochondrial DNA induced mitochondria abnormalities and cellular dysfunction in sporadic PD.
    Molecular Neurobiology 09/2014; DOI:10.1007/s12035-014-8893-4 · 5.29 Impact Factor