Poster Presentation The 45th Lorne Conference on Protein Structure and Function 2020

Structural studies of VDAC2 in BAX/BAK-mediated apoptosis (#115)

Zheng Yuan 1 , Richard W Birkinshaw 1 , Grant Dewson 1 , Peter E Czabotar 1
  1. Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia

Apoptosis is a form of programmed cell death, it removes cells which are no longer needed or are dangerous and is key for development, immune system function and tumour suppression. The BCL‑2 family members, BAX and BAK, are essential mediators of apoptosis, as they execute and regulate the intrinsic apoptotic pathway upon a death stimulus1. It has previously been shown that voltage dependent anion channel 2 (VDAC2) binds to BAK and BAX at the mitochondrial outer membrane (MOM) and regulates their apoptotic function2,3. In healthy cells, BAX and BAK are found to form distinct complexes with VDAC2 at the mitochondria that dissociate upon an apoptotic stimulus4. The apoptosis inhibitor WEHI-9625 has been reported to bind VDAC2 and selectively block apoptosis driven by murine BAK (mBAK)5, also highlight the interaction between BAK and VDAC2 as a promising drug target to manipulate apoptosis.

This project aims to investigate the role of these complexes in BAX/BAK-mediated apoptosis and provide structural information regarding the BAK: VDAC2 and BAX: VDAC2 complexes. We use X-ray crystallography and Cryo-EM techniques to study structures of these protein complexes, SPR and thermal shift assays to understand interactions between the small molecule WEHI-9625 and VDAC2. These studies will provide us further insights into BAX/BAK-mediated apoptotic pathways and how can we manipulate apoptosis via the protein VDAC2. We have purified recombinant VDAC2 by refolding and did some binding assays with the small molecule WEHI-9625. In the meantime, we are in the process of purifying the BAK: VDAC2 complex for later Cryo-EM studies.

  1. Czabotar, P.E., Lessene, G., Strasser, A. & Adams, J.M. Control of apoptosis by the BCL-2 protein family: implications for physiology and therapy. Nat Rev Mol Cell Biol 15, 49-63 (2014).
  2. Cheng, E.H., Sheiko, T.V., Fisher, J.K., Craigen, W.J. & Korsmeyer, S.J. VDAC2 inhibits BAK activation and mitochondrial apoptosis. Science 301, 513-7 (2003).
  3. Chin, H.S. et al. VDAC2 enables BAX to mediate apoptosis and limit tumor development. Nat Commun 9, 4976 (2018).
  4. Ma, S.B. et al. Bax targets mitochondria by distinct mechanisms before or during apoptotic cell death: a requirement for VDAC2 or Bak for efficient Bax apoptotic function. Cell Death Differ 21, 1925-35 (2014).
  5. van Delft, M.F. et al. A small molecule interacts with VDAC2 to block mouse BAK-driven apoptosis. Nat Chem Biol (2019).