Mediation of the Antiapoptotic Activity of Bcl-xL Protein upon Interaction with VDAC1 Protein
ABSTRACT The mitochondrial protein, the voltage-dependent anion channel (VDAC), is implicated in the control of apoptosis, including via its interaction with the pro- and antiapoptotic proteins. We previously demonstrated the direct interaction of Bcl2 with VDAC, leading to reduced channel conductance. VDAC1-based peptides interacted with Bcl2 to prevent its antiapoptotic activity. Here, using a variety of approaches, we show the interaction of the antiapoptotic protein, Bcl-xL, with VDAC1 and reveal that this interaction mediates Bcl-xL protection against apoptosis. C-terminally truncated Bcl-xL(Δ21) interacts with purified VDAC1, as revealed by microscale thermophoresis and as reflected in the reduced channel conductivity of bilayer-reconstituted VDAC1. Overexpression of Bcl-xL prevented staurosporine-induced apoptosis in cells expressing native VDAC1 but not certain VDAC1 mutants. Having identified mutations in VDAC1 that interfere with the Bcl-xL interaction, certain peptides representing VDAC1 sequences, including the N-terminal domain, were designed and generated as recombinant and synthetic peptides. The VDAC1 N-terminal region and two internal sequences were found to bind specifically, and in a concentration- and time-dependent manner, to immobilized Bcl-xL(Δ21), as revealed by surface plasmon resonance. Moreover, expression of the recombinant peptides in cells overexpressing Bcl-xL prevented protection offered by the protein against staurosporine-induced apoptosis. These results point to Bcl-xL acting as antiapoptotic protein, promoting tumor cell survival via binding to VDAC1. These findings suggest that interfering with Bcl-xL binding to the mitochondria by VDAC1-based peptides may serve to induce apoptosis in cancer cells and to potentiate the efficacy of conventional chemotherapeutic agents.
- SourceAvailable from: Barbara Mertins
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- "mitochondrial membrane, VDACs interact directly with a plethora of pro-and anti-apoptotic factors, either members of the Bcl-2 protein family such as Bcl-xL (Arbel et al., 2012; Malia and Wagner, 2007), Bid/tBid(Rostovtseva et al., 2004), Bax/Bak, (Shimizu et al., 2001), hexokinases (Godbole et al., 2013) or Bnip3 (Chaanine et al., 2013). The precise molecular functions and stoichiometries of these VDAC/apoptotic factor complexes are poorly understood, although tentative structural predictions for several VDAC/effector complexes have been suggested (G.Veresov and Davidovskii, 2014). "
ABSTRACT: Abstract Voltage dependent anion channels (VDAC) are the most abundant proteins in the outer mitochondrial membrane. Although they are essential in metabolite exchange, cell defense and apoptosis, the molecular mechanism of these VDAC-mediated processes remains elusive. Here we review recent progress in terms of VDACs' structure and regulation with a special focus on the molecular aspects of gating and the interaction with effector proteins.
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- "Of note, while some authors proposed that the MPT would stem from an unselectively open conformation of the PTPC , others concluded that the MPT would originate from the closed state of the pore  . Irrespective of this controversy, which has not yet been fully resolved, recent data have confirmed a critical role for the interaction between VDAC1 and BCL-X L in the antiapoptotic properties of the latter . Interestingly, many other BCL-2 family members such as BAX, BAK, BID, and BCL-2 appear to interact with (and hence modulate the activity of) PTPC components (i.e., VDAC1, VDAC2, and ANT)    , suggesting that the crosstalk between these two systems might constitute a particularly important point of functional regulation. "
ABSTRACT: The BCL-2 homolog BCL-XL, one of the two protein products of BCL2L1, has originally been characterized for its prominent prosurvival functions. Similar to BCL-2, BCL-XL binds to its multidomain proapoptotic counterparts BAX and BAK, hence preventing the formation of lethal pores in the mitochondrial outer membrane, as well as to multiple BH3-only proteins, thus interrupting apical proapoptotic signals. In addition, BCL-XL has been suggested to exert cytoprotective functions by sequestering a cytosolic pool of the pro-apoptotic transcription factor p53 and by binding to the voltage-dependent anion channel 1 (VDAC1), thereby inhibiting the so-called mitochondrial permeability transition (MPT). Thus, BCL-XL appears to play a prominent role in the regulation of multiple distinct types of cell death, including apoptosis and regulated necrosis. More recently, great attention has been given to the cell death-unrelated functions of BCL-2-like proteins. In particular, BCL-XL has been shown to modulate a number of pathophysiological processes, including-but not limited to-mitochondrial ATP synthesis, protein acetylation, autophagy and mitosis. In this short review article, we will discuss the functions of BCL-XL at the interface between cell death and metabolism.International Journal of Cell Biology 02/2013; 2013:705294. DOI:10.1155/2013/705294
- Biochimica et Biophysica Acta (BBA) - Bioenergetics; 10/2012