Investigation of BOK, a poorly understood Bcl-2 family protein — ASN Events
  1. Schedule
  2. Session Five - Poster Session A including Refreshments
  3. Investigation of BOK, a poorly understood Bcl-2 family protein

Investigation of BOK, a poorly understood Bcl-2 family protein (#152)

Angus D Cowan 1 2 , Peter M Colman 1 2 , Peter E Czabotar 1 2
  1. Medical Biology, University of Melbourne, Melbourne, VIC, Australia
  2. Structural Biology, The Walter and Eliza Hall Institute, Melbourne, VIC, Australia

Programmed cell death, or apoptosis, is responsible for the removal of damaged or stressed cells. The Bcl-2 protein family regulates the intrinsic apoptotic pathway by controlling mitochondrial outer membrane permeabilisation (MOMP), the “point of no return” in this cell death pathway. Proteins in this family contain regions of structural and sequence homology known as Bcl-2 homology (BH) domains and function either in a pro-apoptotic or pro-survival manner. The pro-survival proteins sequester and restrain pro-apoptotic relatives, preventing MOMP1. Proteins of the pro-apoptotic BH3-only protein subfamily are directly and/or indirectly responsible for the activation of critical pathway effectors BAX and BAK1,2,3. Activated BAX and BAK homodimerise and oligomerise on the mitochondrial outer membrane resulting in MOMP1. Bcl-2-related ovarian killer protein (BOK) shares high sequence identity with BAX and BAK and its overexpression causes MOMP4. However, mice lacking Bax and Bak exhibit severe developmental abnormalities and cells derived from these mice are resistant to most, if not all apoptotic stimuli despite detectable BOK expression5. It has recently been demonstrated that BAX and/or BAK are largely required for MOMP to occur upon BOK overexpression4. It is therefore unlikely that these proteins overlap functionally in relation to apoptosis. Details of the structure and function of BOK have remained elusive despite 16 years of investigation since its discovery, due in part to the lack of a suitable recombinant expression system. We have produced recombinant BOK for the first time and begun structural studies and characterisation of its function in vitro. Using liposomal release and binding assays, we assess the capacity of BOK to permeabilise lipid bilayers and its binding affinity for pro-survival and BH3-only proteins. 

  1. Youle, R. J. & Strasser, A. (2008) “The BCL-2 protein family: opposing activities that mediate cell death” Nat. Rev. Mol. Cell Biol. 9:47–59.
  2. Kuwana, T., Bouchier-Hayes, L., Chipuk, J.E., Bonzon, C., Sullivan, B.A., Green, D.R., and Newmeyer, D.D. (2005) “BH3 Domains of BH3-Only Proteins Differentially Regulate Bax-Mediated Mitochondrial Membrane Permeabilization Both Directly and Indirectly” Mol. Cell 17:525–535.
  3. Czabotar, P.E., Westphal, D., Dewson, G., Ma, S., Hockings, C., Fairlie, W.D., Lee, E.F., Yao, S., Robin, A.Y., Smith, B.J., et al. (2013). Bax crystal structures reveal how BH3 domains activate Bax and nucleate its oligomerization to induce apoptosis. Cell 152: 519–531.
  4. Echeverry, N., Bachmann, D., Ke, F., Strasser, A., Simon, H.U., and Kaufmann, T. (2013) “Intracellular localization of the BCL-2 family member BOK and functional implications” Cell Death Differ. 20:785-789.
  5. Ke, F., Voss, A., Kerr, J.B., O'Reilly, L.A., Tai, L., Echeverry, N., Bouillet, P., Strasser, A., and Kaufmann, T. (2012). BCL-2 family member BOK is widely expressed but its loss has only minimal impact in mice. Cell Death Differ 19: 915–925.