Mitochondrial Ceramide-Rich Macrodomains Functionalize Bax upon Irradiation
| Autor: | Andreas Rimner, Govind Ragupathi, Jimmy A. Rotolo, Desiree Ehleiter, John C. Reed, Judith Mesicek, Hyunmi Lee, Richard Kolesnick, Zvi Fuks, Wen-Chieh Liao, Adriana Haimovitz-Friedman, Xianglei Yin, Erich Gulbins, Tuula Penate-Medina, Dayong Zhai |
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| Jazyk: | angličtina |
| Rok vydání: | 2011 |
| Předmět: |
Medizin
lcsh:Medicine Apoptosis Mitochondrion HeLa Mice chemistry.chemical_compound 0302 clinical medicine Radiation Ionizing Molecular Cell Biology lcsh:Science bcl-2-Associated X Protein Cellular Stress Responses 0303 health sciences Multidisciplinary Cell Death biology Chemistry Cytochrome c Cellular Structures Mitochondria Cell biology 030220 oncology & carcinogenesis Mitochondrial Membranes Membranes and Sorting Oxidoreductases Research Article Signal Transduction Ceramide Ceramides Fumonisins Permeability 03 medical and health sciences Bcl-2-associated X protein Animals Humans Protein Structure Quaternary Biology 030304 developmental biology lcsh:R Correction Radiobiology Lipid signaling biology.organism_classification Molecular Weight Membrane protein biology.protein Cattle lcsh:Q HeLa Cells |
| Zdroj: | PLoS ONE, Vol 6, Iss 6, p e19783 (2011) PLoS ONE |
| ISSN: | 1932-6203 |
| Popis: | Background: Evidence indicates that Bax functions as a "lipidic" pore to regulate mitochondrial outer membrane permeabilization (MOMP), the apoptosis commitment step, through unknown membrane elements. Here we show mitochondrial ceramide elevation facilitates MOMP-mediated cytochrome c release in HeLa cells by generating a previously-unrecognized mitochondrial ceramide-rich macrodomain (MCRM), which we visualize and isolate, into which Bax integrates. Methodology/Principal Findings: MCRMs, virtually non-existent in resting cells, form upon irradiation coupled to ceramide synthase-mediated ceramide elevation, optimizing Bax insertion/oligomerization and MOMP. MCRMs are detected by confocal microscopy in intact HeLa cells and isolated biophysically as a light membrane fraction from HeLa cell lysates. Inhibiting ceramide generation using a well-defined natural ceramide synthase inhibitor, Fumonisin B1, prevented radiation-induced Bax insertion, oligomerization and MOMP. MCRM deconstruction using purified mouse hepatic mitochondria revealed ceramide alone is non-apoptogenic. Rather Bax integrates into MCRMs, oligomerizing therein, conferring 1-2 log enhanced cytochrome c release. Consistent with this mechanism, MCRM Bax isolates as high molecular weight "pore-forming" oligomers, while non-MCRM membrane contains exclusively MOMP-incompatible monomeric Bax. Conclusions/Significance: Our recent studies in the C. elegans germline indicate that mitochondrial ceramide generation is obligate for radiation-induced apoptosis, although a mechanism for ceramide action was not delineated. Here we demonstrate that ceramide, generated in the mitochondrial outer membrane of mammalian cells upon irradiation, forms a platform into which Bax inserts, oligomerizes and functionalizes as a pore. We posit conceptualization of ceramide as a membrane-based stress calibrator, driving membrane macrodomain organization, which in mitochondria regulates intensity of Bax-induced MOMP, and is pharmacologically tractable in vitro and in vivo. © 2011 Lee et al. |
| Databáze: | OpenAIRE |
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