DRP-1 functions independently of mitochondrial structural perturbations to facilitate BH3 mimetic-mediated apoptosis
Authors: Mateus Milani
Shankar Varadarajan
Xu Luo
Aoula Al-Zebeeby
Alison J Beckett
Ian A Prior
Gerald M Cohen
Journal: Cell Death Discovery (2019)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: Cell death; Organelles.
Affiliations: 1Department of Molecular and Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, Liverpool, Ashton Street, Liverpool, L69 3GE UK., 2Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, Ashton Street, Liverpool, L69 3GE UK., 3Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198 USA.

Abstract:  Maintenance of mitochondrial integrity is critical for normal cellular homoeostasis. Most cells respond to stress stimuli and undergo apoptosis by perturbing mitochondrial structure and function to release proteins, such as cytochrome c, which are essential for the execution of the intrinsic apoptotic cascade. Cancer cells evade these events by overexpressing the anti-apoptotic BCL-2 family of proteins on mitochondrial membranes. Inhibitors of the anti-apoptotic BCL-2 family proteins, also known as BH3 mimetics, antagonise the pro-survival functions of these proteins and result in rapid apoptosis. Although the precise mechanism by which BH3 mimetics induce apoptosis has been well characterised, not much is known in terms of the structural changes that occur in mitochondria during apoptosis. Using a panel of highly selective BH3 mimetics and a wide range of cell lines, we demonstrate that BH3 mimetics induce extensive mitochondrial fission, accompanied by swelling of the mitochondrial matrix and rupture of the outer mitochondrial membrane. These changes occur in a BAX/ BAK-dependent manner. Although a major mitochondrial fission GTPase, DRP-1, has been implicated in mitochondrial apoptosis, our data demonstrate that DRP-1 might function independently/downstream of BH3 mimetic-mediated mitochondrial fission to facilitate the release of cytochrome c and apoptosis. Moreover, downregulation of DRP-1 prevented cytochrome c release and apoptosis even when OPA1, a protein mediating mitochondrial fusion, was silenced. Although BH3 mimetic-mediated displacement of BAK and other BH3-only proteins from BCL-XL and MCL-1 was unaffected by DRP-1 downregulation, it prevented BAK activation significantly, thus placing DRP-1 as one of the most critical players, along with BAX and BAK, that governs BH3 mimetic-mediated cytochrome c release and apoptosis. 

Retracted: No

PubPeer comments:
 Figure 4B: two panels (red boxes) appear to be much more similar than expected after vertical flip and stretching. Could the authors please post here the uncropped scan of the blots at high resolution and take away any concerns? ![file] , 
 Figure 6, immunoprecipitation (IP) showing that NPSN11 interacts with the syntaxin KNOLLE. Blue boxes: bands appear to be much more similar than expected. Could the authors please post here the uncropped scan of the blots at high resolution and take away any concerns? ![file] , 
 #2 A more detailed analysis. NPSN11 band (2) has been vertically compressed of about 10%. The blue arrow points to a light area, where a brush tool could have been used. Could the authors please post here the uncropped scan of the blots at high resolution and take away any concerns? ![file] ,