Cancer arises as a result of the inability of damaged cells to initiate a signaling cascade that results in thedestruction of the cell and clearance from the body. This process, known as apoptosis, is necessary toprevent reproduction of damaged cells that leads to cancer. A family of proteins known as the Bcl-2 proteinfamily regulates apoptosis. The Bcl-2 protein family works to promote cell death through the interaction ofdeath promoting proteins. Bax, a pro-apoptotic member of this family, initiates the cell death cascade byreleasing cytochrome C. Bax has the ability to mediate cytochrome c release by working in conjunction withcardiolipin. Previous studies have shown that the presence of cardiolipin enhances the ability of Bax to formpores in reconstituted membranes through an, as yet, unknown mechanism. Preliminary data from our labhas begun to elucidate the mechanism of interaction between Bax and cardiolipin. In the presence ofcardiolipin Bax undergoes a unique conformational change that facilitates the release of molecules frommodel membranes. The goals of the current project are to determine the impact that this conformationalchange has on the active and functional conformation of Bax. Our goals are to detail the structural changesand to correlate these changes with the function of Bax at the membrane. This will be achieved by studyingpore formation and oligomerization of membrane-associated Bax using fluorescent spectroscopictechniques. We will also study how regions of Bax contribute to membrane recognition pore formation andoligomerization through the use of mutants. The two regions of Bax that are of interest are the BH3 domain,also called the putative cardiolipin binding region, and the c-terminal hydrophobic domain. Understandingthe mechanisms of pore formation and oligomerization as well as how domains of Bax contribute to themembrane-active conformation will enhance our understanding of apoptosis and aid in our ability toovercome the barriers that cancer cells erect to evade apoptosis.
