The over-arching aim of this project is to uncover shared mechanisms that govern developmental and pathologic neuron death and to apply this knowledge to formulate treatments for stroke, trauma and neurodegenerative disorders. The proposed studies will focus on the "apoptotic cell cycle pathway" studied in depth under this grant that plays a required role in a variety of developmental and pathological neuron death paradigms. In this pathway, the cyclin-dependent kinase-4 (Cdk4) is activated in neurons in response to apoptotic stimuli. This is turn phosphorylates Rb pocket protein family members causing them to dissociate from gene-repressor complexes with the E2F transcription factors. Dissociation of Rb-E2F repressor complexes leads to derepression and induction of Myb transcription factors that bind to and activate the promoter for apoptotic proteins including Bim. Induction of Bim promotes release of mitochondrial proteins and activation of caspases, resulting in neuron death. This proposal focuses on the mechanism by which apoptotic stimuli activate Cdk4 and in particular on the cdc25a phosphatase. During the cell cycle, cdc25a activates Cdk4 by removing an inhibitory phosphate group. We will assess the hypothesis that cdc25a activity is elevated by apoptotic stimuli in neurons and that this is an apical event in triggering the apoptotic cell cycle pathway. Preliminary supportive data include findings that cdc25a protein and transcripts are elevated in neuronal cells by several different apoptotic stimuli, and that knockdown or chemical inhibition of cdc25a is neuroprotective. There are two specific aims. 1). To test, in in vitro models, the hypothesis that cdc25a plays a proximal role in developmental and pathological neuron death and to dissect the up- and downstream elements of the apoptotic cell cycle cascade in which it partakes. This will involve a variety of cell cultue systems and models for developmental (NGF deprivation) and pathological (AD, PD) neuron death. We will explore a) the required role of cdc25a in neuron death in our various models, b) the extent of cdc25a regulation by apoptotic stimuli, c) the death cascade components that lie downstream of cdc25a, and d) the upstream mechanisms by which cdc25a expression and activity are regulated and how these are engaged by apoptotic stimuli. We will be particularly keen to identify feed-forward death loops involving cdc25a. 2). To test the hypothesis that cdc25a is required for developmental neuron death in vivo. Using the paradigm of developmental neuron death in superior cervical ganglia, we will query whether a) cdc25a levels are induced in dying neurons, b) selected downstream cell cycle pathway components are co-elevated in such neurons, c) biologically-tolerated chemical cdc25a inhibitors suppress neuron death in this system and d) whether such death is inhibited by selective genetic ablation of cdc25a in sympathetic ganglia. Current findings indicate that cdc25a is a druggable target whose in vivo inhibition has little side effects. Thus success of the current aims has a clear potential to lead to development of therapies for pathologic neuron death.

Public Health Relevance

Neuron death occurs during normal development as well as in a variety of pathological conditions including stroke, trauma and neurodegeneration. The studies in this proposal seek to understand a key step in neuron death involving the protein cdc25a. Inhibitors of cdc25a have been produced that have few side effects in animals and if the proposed studies show as anticipated that cdc25a is required for pathological neuron death, such inhibitors may have valuable therapeutic potential for stoke, trauma and neurodegeneration.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS033689-19
Application #
8435110
Study Section
Neural Oxidative Metabolism and Death Study Section (NOMD)
Program Officer
Corriveau, Roderick A
Project Start
1994-12-01
Project End
2018-01-31
Budget Start
2013-02-01
Budget End
2014-01-31
Support Year
19
Fiscal Year
2013
Total Cost
$469,106
Indirect Cost
$173,474
Name
Columbia University (N.Y.)
Department
Pathology
Type
Schools of Medicine
DUNS #
621889815
City
New York
State
NY
Country
United States
Zip Code
10032
Akpan, Nsikan; Troy, Carol M (2013) Caspase inhibitors: prospective therapies for stroke. Neuroscientist 19:129-36
Zareen, N; Biswas, S C; Greene, L A (2013) A feed-forward loop involving Trib3, Akt and FoxO mediates death of NGF-deprived neurons. Cell Death Differ 20:1719-30
Jean, Ying Y; Ribe, Elena M; Pero, Maria Elena et al. (2013) Caspase-2 is essential for c-Jun transcriptional activation and Bim induction in neuron death. Biochem J 455:15-25
Wilhelm, Michael; Kukekov, Nickolay V; Schmit, Travis L et al. (2012) Sh3rf2/POSHER protein promotes cell survival by ring-mediated proteasomal degradation of the c-Jun N-terminal kinase scaffold POSH (Plenty of SH3s) protein. J Biol Chem 287:2247-56
Willett, Ryan T; Greene, Lloyd A (2011) Gata2 is required for migration and differentiation of retinorecipient neurons in the superior colliculus. J Neurosci 31:4444-55
Biswas, Subhas C; Zhang, Yi; Iyirhiaro, Grace et al. (2010) Sertad1 plays an essential role in developmental and pathological neuron death. J Neurosci 30:3973-82
Levy, Oren A; Malagelada, Cristina; Greene, Lloyd A (2009) Cell death pathways in Parkinson's disease: proximal triggers, distal effectors, and final steps. Apoptosis 14:478-500
Sproul, Andrew A; Xu, Zhiheng; Wilhelm, Michael et al. (2009) Cbl negatively regulates JNK activation and cell death. Cell Res 19:950-61
Li, Guangfu; Li, Wenhong; Angelastro, James M et al. (2009) Identification of a novel DNA binding site and a transcriptional target for activating transcription factor 5 in c6 glioma and mcf-7 breast cancer cells. Mol Cancer Res 7:933-43
Greene, Lloyd A; Lee, Hae Young; Angelastro, James M (2009) The transcription factor ATF5: role in neurodevelopment and neural tumors. J Neurochem 108:11-22

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