Characterization of a novel pro-apoptotic role for nuclear associated BCL-2
Bryce Patrick Portier
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Both stroke and cancer are major public health problems that inflict immeasurable suffering to victims and their families. The treatment options currently in place for both stroke victims and cancer patients are limited. The underlying unifying characteristic of both conditions is that they are the end result of abrogation of apoptosis regulation. In the case of stroke, an initial increase in Bcl-2 expression traditionally follows ischemia/re-perfusion. A major goal of stroke therapy is to rescue the peri-ischemic region of cells that have up-regulated Bcl-2 but have not yet committed to the execution phase of apoptosis. A strong potential target to save neurons and supporting glia is to modulate Bcl-2 expression or localization in order to promote an anti-apoptotic function. Likewise, in the case of cancer, 80% of all tumors over-express Bcl-2. While malignant cells utilize mitochondrial localized Bcl-2 to gain protection from apoptosis, possession of Bcl-2 makes these cells a target for treatments that could alter Bcl-2’s localization and potentially promote apoptosis by altering Bcl-2’s sub-cellular localization/function. Thus, my Ph.D. project has focused on understanding the role of nuclear localized Bcl-2, Bcl-2’s default sub-cellular localization, and on the mechanism of binding between Bcl-2 and its mitochondrial chaperone protein FKBP38. My work has characterized the function of nuclear-associated Bcl-2 as a pro-apoptotic protein and Bcl-2’s BH4 domain as a critical domain for binding the chaperone protein FKBP38. Based on these findings we attempted a strategy for interfering with Bcl-2/FKBP38 binding via addition of a BH4 domain peptide both in vivo and in vitro. In both cases, addition of a BH4 domain peptide disrupted Bcl-2/FKBP38 binding, increased the level of nuclear associated Bcl-2, and induced apoptosis selectively in Bcl-2 bearing cells. The rationale behind this project was to determine molecular events underscoring Bcl-2’s localization and function in order to identify novel therapeutic targets for treatment of conditions that would benefit from interventions that modify the execution of apoptosis. The long term goal spawning from my Ph.D. thesis project is to further our understanding of apoptotic control mechanisms and in turn develop future therapies to control diseases due to abrogation of apoptotic regulation.