Dissecting the Mitochondrial Translocation Mechanism of Anti-Apoptotic BCL-w

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PROJECT SUMMARY/ABSTRACT BCL-2 family proteins are key regulators of apoptosis, a form of programmed cell death essential to normal development and tissue homeostasis. Deregulation of the apoptotic machinery can lead to a host of human diseases characterized by too many or too few cells. Pathologic enforcement of cell survival by anti-apoptotic BCL-2 family proteins, which bind to and inactivate the BAX/BAK initiators of cell death, can lead to the development, maintenance, and chemoresistance of human cancer. In particular, anti-apoptotic BCL-w has been linked to the progression and invasiveness of a broad range of human cancers. BCL-w is believed to migrate from cytosol to mitochondria in response to interaction with BH3-only members of the BCL-2 family, but the physiological triggers and structure-function mechanism of BCL-w translocation are unknown. The Walensky lab has previously employed stapled “BH3” peptides, which recapitulate the natural structure and function of this critical signaling domain, to identify a novel regulatory site on pro-apoptotic BAX that mediates its mitochondrial translocation and resultant induction of apoptosis. Specifically, BH3 engagement of a groove formed by the juxtaposition of α-helices 1 and 6 of BAX induces allosteric release of its C-terminal helix for mitochondrial targeting and insertion. I hypothesize that BCL-w, as an anti-apoptotic homologue of BAX, may likewise be subject to regulation of its subcellular distribution. To elucidate the BCL-w translocation mechanism, I aim to: (1) synthesize and characterize stabilized alpha-helix of BCL-2 domains (SAHBs) modeled after BH3 helices to assess their functional interactions with anti-apoptotic BCL-w; (2) locate the binding interface and induced conformational changes associated with BH3-triggered BCL-w translocation; and (3) investigate the physiologic implications of stress-induced BCL-w translocation in cancer. Thus, the overarching goal of my proposal is to characterize the structure-function mechanism for ligand-stimulated BCL- w translocation and determine its contribution to enforcing apoptotic resistance in human cancer. I believe this study could inform a novel therapeutic strategy to disarm BCL-w in cancer by targeted disruption of the binding interface that drives its mitochondrial translocation. I am eager to embark on the rigorous training program proposed for my graduate studies at Harvard Medical School and the Dana-Farber Cancer Institute and look forward to developing as an independent and innovative investigator at the interface of chemical biology, apoptosis research, and cancer medicine.