This revised R01 application focuses on pursuing our recent finding that dominant negative inhibitors of the Egr family of transcription regulatory factors represent a novel and highly effective means of suppressing activation of c-Jun. This observation emerged from our studies demonstrating that Egr inhibitor constructs block NGF induced neurite outgrowth in PC12 cells. In studies aimed at understanding how they exerted this effect, we have obtained compelling preliminary evidence that they do so by blocking the ability of NGF to induce phosphorylation and activation of c-Jun. Since c-Jun activation plays a critical role in several neuronal apoptosis paradigms, we examined whether Egr inhibitor constructs are effective in this context as well. To this end, we have found that Egr inhibitors are highly effective in protecting cerebellar granule cells from apoptotic cell death induced by potassium deprivation. Furthermore, we have obtained compelling evidence that they do so by blocking c-Jun activation. In preliminary studies aimed at deciphering the mechanism(s) mediating this effect, we have identified a novel effect of Egri, the prototype Egr family member, on c-Jun. We have found that Egri co-precipitates with c-Jun. This novel finding suggests that Egr proteins may control c-Jun activation via protein-protein interactions, rather than via its conventional mode of action, i.e. control of target gene expression by binding to its cognate DNA response element. Based on these findings, the overall goal of this proposal is to define how Egr family members control c-Jun activation and assess whether Egr inhibitors are also effective in blocking cell death in other neuronal apoptosis paradigms that are dependent on c-Jun activation.
