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The major focus of our laboratory is the study of the molecular mechanisms of neuronal dysfunction and death with an emphasis on the regulation of caspase activity.
Neuronal loss is an outstanding feature of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and ischemic stroke. We employ model systems of neuronal death to define the death pathways. We are particularly interested in the regulation of the caspases, the multi-membered family of death proteases that are central to the execution of death. Current death paradigms under study include β-amyloid toxicity, peroxynitrite mediated death, neurotrophin-withdrawal-induced death and in vivo models of ischemia. We have developed specific molecular tools for knocking down individual members of the death pathways in post-mitotic (neuronal) cells and for blocking caspase activity/activation in cultured neurons and in vivo.
We have shown that the specificity of the death pathway is determined by the stimulus inducing death but also that there is flexibility in the pathways chosen for executing death. The dominant pathway depends on the relative concentrations of anti- and pro-apoptotic proteins. This illustrates that the maintenance of life and execution of death of a neuron is a delicate balance of the pro- and anti-apoptotic molecules in the cell, a balance that can be altered in disease.
Our studies of oxidative stress mediated death show that cytokines can induce an autocrine mediated death. Down-regulation of superoxide dismutase 1 leads to activation of caspase-1 which releases the cytokine interleukin-1b and the cells undergo a peroxynitrite-dependent death. Thus, although caspase-1 has been defined as a non-apoptotic caspase with a role in inflammation, in response to specific death stimuli caspase-1 can activate a death pathway. It is important to understand the interaction that can occur between the cytokine signaling pathway and the death pathway to determine the appropriate intervention that will result in increased neuronal survival.
