Signaling Pathways Regulating Neuronal Survival

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DESCRIPTION (provided by the applicant): Apoptosis is a specific mode by which cells of all types including neurons, die. While a normal feature of the developing nervous system, apoptotic death of neurons also occurs in neurodegenerative diseases, following stroke and traumatic injury, and upon exposure to neurotoxins. In these cases, apoptosis is undesirable and often leads to serious neurological deficits. The mechanisms by which these different physiological and pathophysiological stimuli abrogate the signaling pathways that normally maintain neuronal survival are far from clear. The signal transduction pathways mediating cell survival and the molecular components that comprise them can be conveniently studied in culture. Such studies have identified many molecules that are likely to be important in regulating survival of neurons in vitro as well as in vivo and which might be affected by neurotoxic stimuli or in neuropathologic conditions. The goal of this application is to examine the role of two known survival-regulatory molecules-the Akt kinase and the nuclear factor-KB (NF- kappaB) transcription factor-in a well established paradigm of neuronal apoptosis that uses cultures of rat cerebellar granule neurons. Survival of these neurons in culture can be maintained by at least four factors-elevated extracellular potassium (high K+ or HK), IGF- 1, cyclic AMP, and lithium. Although activating distinct molecules at the cell-surface, our hypothesis is that the signaling pathways utilized by these different survival factors converge on Akt and/or NF- kappaB. The specific aims of the application are as follows: 1. Knowing that Akt is necessary for IGF-l- mediated survival, to determine whether it is also involved in survival promotion by HK, cyclic AMP, and lithium. 2. To determine the mechanism by which NF- kappaB mediates survival by HK and to examine whether it is also required for survival by IGF- 1, cyclic AMP, and lithium. Special emphasis will be placed on the roles of the transcriptional coactivator, CBP, and the NF-kappaB inhibitor, IkappaB-B. 3. To determine the relationship between Akappat and NF-kappaB activation in the inhibition of apoptosis.