Open Access
Oligomeric Bax is a component of the putative cytochrome c release channel MAC, mitochondrial apoptosis-induced channel
(American Society for Cell Biology, 2005-03-16) Dejean, Laurent M.; Martínez-Caballero, Sonia; Guo, Liang; Hughes, Cynthia; Teijido Hermida, Óscar; Ducret, Thomas; Ichas, François; Korsmeyer, Stanley J.; Antonsson, Bruno; Jonas, Elizabeth A.; Kinnally, Kathleen W.; Ciencias de la Salud; Osasun Zientziak
Bcl-2 family proteins regulate apoptosis, in part, by controlling formation of the mitochondrial apoptosis-induced channel (MAC), which is a putative cytochrome c release channel induced early in the intrinsic apoptotic pathway. This channel activity was never observed in Bcl-2-overexpressing cells. Furthermore, MAC appears when Bax translocates to mitochondria and cytochrome c is released in cells dying by intrinsic apoptosis. Bax is a component of MAC of staurosporine-treated HeLa cells because MAC activity is immunodepleted by Bax antibodies. MAC is preferentially associated with oligomeric, not monomeric, Bax. The single channel behavior of recombinant oligomeric Bax and MAC is similar. Both channel activities are modified by cytochrome c, consistent with entrance of this protein into the pore. The mean conductance of patches of mitochondria isolated after green fluorescent protein-Bax translocation is significantly higher than those from untreated cells, consistent with onset of MAC activity. In contrast, the mean conductance of patches of mitochondria indicates MAC activity is present in apoptotic cells deficient in Bax but absent in apoptotic cells deficient in both Bax and Bak. These findings indicate Bax is a component of MAC in staurosporine-treated HeLa cells and suggest Bax and Bak are functionally redundant as components of MAC.
Open Access
Regulation of Bax mitochondrial localization by Bcl-2 and Bcl-xL: keep your friends close but your enemies closer
(Elsevier, 2013) Renault, Thibaud T.; Teijido Hermida, Óscar; Antonsson, Bruno; Dejean, Laurent M.; Manon, Stéphen; Ciencias de la Salud; Osasun Zientziak
Bax-induced mitochondrial outer membrane permeabilization (MOMP) is considered as one of the key control switches of apoptosis. MOMP requires Bax relocation to and insertion into the outer mitochondrial membrane to oligomerize and form pores allowing the release of apoptogenic factors such as cytochrome c. Even if these essential steps are now well-defined, it is necessary to better understand the molecular changes underlying the switch between inactive Bax and active (pore-forming) Bax. One of the ongoing issues is to determine whether Bax mitochondrial translocation is a critical step in the control of Bax activation or if this control is carried by latter regulatory steps. In this focus article we discuss recent data suggesting that although Bcl-2 and Bcl-xL block the MOMP, they can also regulate the mitochondrial Bax content. A new model in which Bax inhibition by Bcl-xL occurs at the immediate proximity of the outer mitochondrial membrane is also discussed. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.
Open Access
Bcl-xL stimulates Bax relocation to mitochondria and primes cells to ABT-737
(Elsevier, 2015) Renault, Thibaud T.; Teijido Hermida, Óscar; Missire, Florent; Ganesan, Yogesh Tengarai; Velours, Gisèle; Arokium, Hubert; Beaumatin, Florian; Llanos, Raul; Athané, Axel; Camougrand, Nadine; Priault, Muriel; Antonsson, Bruno; Dejean, Laurent M.; Manon, Stéphen; Ciencias de la Salud; Osasun Zientziak
Open Access
The cytosolic domain of human Tom22 modulates human Bax mitochondrial translocation and conformation in yeast
(Elsevier, 2012) Renault, Thibaud T.; Grandier-Vazeille, Xavier; Arokium, Hubert; Velours, Gisèle; Camougrand, Nadine; Priault, Muriel; Teijido Hermida, Óscar; Dejean, Laurent M.; Manon, Stéphen; Ciencias de la Salud; Osasun Zientziak
The role of the mitochondrial protein receptor Tom22p in the interaction of pro-apoptotic protein Bax with yeast mitochondria was investigated. Co-immunoprecipitation assays showed that human Bax interacted with different TOM subunits, including Tom22p. Expression of the cytosolic receptor domain of human Tom22 increased Bax mitochondrial localization, but decreased the proportion of active Bax. BN-PAGE showed that the cytosolic domain of Tom22 interfered with the oligomerization of Bax. These data suggest that the interaction with the cytosolic domain of Tom22 helps Bax to acquire a conformation able to interact with the outer mitochondrial membrane.
Open Access
MAC and Bcl-2 family proteins conspire in a deadly plot
(Elsevier, 2010-01-18) Dejean, Laurent M.; Ryu, Shin-Young; Martínez-Caballero, Sonia; Teijido Hermida, Óscar; Peixoto, Pablo M.; Kinnally, Kathleen W.; Ciencias de la Salud; Osasun Zientziak
Apoptosis is an elemental form of programmed cell death; it is fundamental to higher eukaryotes and essential to mechanisms controlling tissue homeostasis. Apoptosis is also involved in many pathologies including cancer, neurodegenerative diseases, aging, and infarcts. This cell death program is tightly regulated by Bcl-2 family proteins by controlling the formation of the mitochondrial apoptosis-induced channel or MAC. Assembly of MAC corresponds to permeabilization of the mitochondrial outer membrane, which is the so called commitment step of apoptosis. MAC provides the pathway through the mitochondrial outer membrane for the release of cytochrome c and other pro-apoptotic factors from the intermembrane space. While overexpression of anti-apoptotic Bcl-2 eliminates MAC activity, oligomers of the pro-apoptotic members Bax and/or Bak are essential structural component(s) of MAC. Assembly of MAC from Bax or Bak was monitored in real time by directly patch-clamping mitochondria with micropipettes containing the sentinel tBid, a direct activator of Bax and Bak. Herein, a variety of high affinity inhibitors of MAC (iMAC) that may prove to be crucial tools in mechanistic studies have recently been identified. This review focuses on characterization of MAC activity, its regulation by Bcl-2 family proteins, and a discussion of how MAC can be pharmacologically turned on or off depending on the pathology to be treated.
Open Access
A sandwich ELISA for the conformation-specific quantification of the activated form of human Bax
(Elsevier, 2016) Teijido Hermida, Óscar; Ganesan, Yogesh Tengarai; Llanos, Raul; Peton, Ashley; Urtecho, Jean-Baptiste; Soprani, Adauri; Villamayor, Aimee; Antonsson, Bruno; Manon, Stéphen; Dejean, Laurent M.; Ciencias de la Salud; Osasun Zientziak
Open Access
MAC inhibitors antagonize the pro-apoptotic effects of tBid and disassemble Bax / Bak oligomer
(Springer, 2017) Peixoto, Pablo M.; Teijido Hermida, Óscar; Mirzalieva, Oygul; Dejean, Laurent M.; Pavlov, Evgeny V.; Antonsson, Bruno; Kinnally, Kathleen W.; Ciencias de la Salud; Osasun Zientziak
Open Access
Upregulation of Bcl2 inhibits apoptosis-driven BAX insertion but favors BAX relocalization in mitochondria
(FEBS Press, 2010-07-09) Teijido Hermida, Óscar; Dejean, Laurent M.; Ciencias de la Salud; Osasun Zientziak
Protein-protein interactions between the Bcl2 family proteins regulate apoptosis. An imbalance of this interaction network due to the upregulation of the proto-oncogene Bcl2 leads to a resistance to apoptosis associated with tumor formation. Bcl2 overexpression inhibits BAX oligomerization and mitochondrial outer membrane (MOM) permeabilization. However, Bcl2 effects on earlier steps of BAX-mediated apoptosis are not fully understood. Bcl2 overexpression inhibits BAX insertion into the MOM but spontaneously increases BAX relocalization to the mitochondria. Also, a physical interaction between BAX and Bcl2 is necessary for these two effects to occur. Taken together, these results suggest upregulated Bcl2 stabilizes BAX loose binding to mitochondrial membranes, inhibiting its insertion into the MOM and consequently cytochrome c release.
Open Access
Role of mitochondrial ion channels in cell death
(Wiley, 2010-08-16) Ryu, Shin-Young; Peixoto, Pablo M.; Teijido Hermida, Óscar; Dejean, Laurent M.; Kinnally, Kathleen W.; Ciencias de la Salud; Osasun Zientziak
Ion channels located in the outer and inner mitochondrial membranes are key regulators of cellular signaling for life and death. Permeabilization of mitochondrial membranes is one of the most critical steps in the progression of several cell death pathways. The mitochondrial apoptosis-induced channel (MAC) and the mitochondrial permeability transition pore (mPTP) play major roles in these processes. Here, the most recent progress and current perspectives about the roles of MAC and mPTP in mitochondrial membrane permeabilization during cell death are presented. The crosstalk signaling of MAC and mPTP formation/activation mediated by cytosolic Ca2+ signaling, Bcl-2 family proteins, and other mitochondrial ion channels is also discussed. Understanding the mechanisms that regulate opening and closing of MAC and mPTP has revealed new therapeutic targets that potentially could control cell death in pathologies such as cancer, ischemia/reperfusion injuries, and neurodegenerative diseases.