Mitochondria are not required for death receptor-mediated cytosolic acidification during apoptosis. 2007

Michaela Waibel, and Stefan Kramer, and Kirsten Lauber, and Adrian Lupescu, and Joachim Manns, and Klaus Schulze-Osthoff, and Florian Lang, and Sebastian Wesselborg
Department of Internal Medicine I, Eberhard-Karls-University, University of Tübingen, Tübingen, Germany.

In addition to cell shrinkage, membrane blebbing, DNA fragmentation and phosphatidylserine exposure, intracellular acidification represents a hallmark of apoptosis. Although the mechanisms underlying cytosolic acidification during apoptosis remained largely elusive, a pivotal role of mitochondria has been proposed. In order to investigate the involvement of mitochondria in cytosolic acidification during apoptosis, we blocked the mitochondrial death pathway by overexpression of Bcl-2 and subsequently activated the death receptor pathway by anti-CD95 or TRAIL or the mitochondrial pathway by staurosporine. We show that Bcl-2 but not caspase inhibition prevented staurosporine-induced intracellular acidification. Thus, intracellular acidification in mitochondrial apoptosis is a Bcl-2-inhibitable, but caspase-independent process. In contrast, Bcl-2 only slightly delayed, but did not prevent intracellular acidification upon triggering of death receptors. The Na(+)/H(+) exchanger NHE1 was partially degraded during apoptosis but only to a small extent and and at a delayed time point when cytosolic acidification was almost completed. We therefore conclude that cytosolic acidification is mitochondrially controlled in response to mitochondria-dependent death stimuli, but requires additional caspase-dependent mechanisms during death receptor-mediated apoptosis.

UI MeSH Term Description Entries
D008928 Mitochondria Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed) Mitochondrial Contraction,Mitochondrion,Contraction, Mitochondrial,Contractions, Mitochondrial,Mitochondrial Contractions
D003593 Cytoplasm The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990) Protoplasm,Cytoplasms,Protoplasms
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000074082 Sodium-Hydrogen Exchanger 1 A sodium-hydrogen antiporter expressed by many cell types, especially on the basolateral surfaces of EPITHELIAL CELLS. It functions through an inward sodium ion chemical gradient to eliminate acids (protons) generated by metabolism and regulate intracellular pH. It is highly sensitive to AMILORIDE. Na(+)-H(+) Exchanger 1,SLC9A1 Protein,Solute Carrier Family 9 Member 1,Sodium Hydrogen Exchanger 1
D000590 Amino Acid Chloromethyl Ketones Inhibitors of SERINE ENDOPEPTIDASES and sulfhydryl group-containing enzymes. They act as alkylating agents and are known to interfere in the translation process. Peptide Chloromethyl Ketones,Chloromethyl Ketones, Peptide,Ketones, Peptide Chloromethyl
D015853 Cysteine Proteinase Inhibitors Exogenous and endogenous compounds which inhibit CYSTEINE ENDOPEPTIDASES. Acid Cysteine Proteinase Inhibitor,Cysteine Protease Inhibitor,Cysteine Protease Inhibitors,Cysteine Proteinase Antagonist,Cysteine Proteinase Antagonists,Cysteine Proteinase Inhibitor,Cysteine Proteinase Inhibitors, Endogenous,Cysteine Proteinase Inhibitors, Exogenous,alpha-Cysteine Protease Inhibitor,Acid Cysteine Proteinase Inhibitors,alpha-Cysteine Protease Inhibitors,Antagonist, Cysteine Proteinase,Antagonists, Cysteine Proteinase,Inhibitor, Cysteine Protease,Inhibitor, Cysteine Proteinase,Inhibitor, alpha-Cysteine Protease,Inhibitors, Cysteine Protease,Inhibitors, Cysteine Proteinase,Inhibitors, alpha-Cysteine Protease,Protease Inhibitor, Cysteine,Protease Inhibitor, alpha-Cysteine,Protease Inhibitors, Cysteine,Protease Inhibitors, alpha-Cysteine,Proteinase Antagonist, Cysteine,Proteinase Antagonists, Cysteine,Proteinase Inhibitor, Cysteine,Proteinase Inhibitors, Cysteine,alpha Cysteine Protease Inhibitor,alpha Cysteine Protease Inhibitors
D017209 Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, i.e., DNA FRAGMENTATION. It is genetically programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Apoptosis, Extrinsic Pathway,Apoptosis, Intrinsic Pathway,Caspase-Dependent Apoptosis,Classic Apoptosis,Classical Apoptosis,Programmed Cell Death,Programmed Cell Death, Type I,Apoptoses, Extrinsic Pathway,Apoptoses, Intrinsic Pathway,Apoptosis, Caspase-Dependent,Apoptosis, Classic,Apoptosis, Classical,Caspase Dependent Apoptosis,Cell Death, Programmed,Classic Apoptoses,Extrinsic Pathway Apoptoses,Extrinsic Pathway Apoptosis,Intrinsic Pathway Apoptoses,Intrinsic Pathway Apoptosis
D045304 Cytochromes c Cytochromes of the c type that are found in eukaryotic MITOCHONDRIA. They serve as redox intermediates that accept electrons from MITOCHONDRIAL ELECTRON TRANSPORT COMPLEX III and transfer them to MITOCHONDRIAL ELECTRON TRANSPORT COMPLEX IV. Cytochrome c,Ferricytochrome c,Ferrocytochrome c,Apocytochrome C
D053218 Receptors, Death Domain A family of cell surface receptors that signal via a conserved domain that extends into the cell CYTOPLASM. The conserved domain is referred to as a DEATH DOMAIN due to the fact that many of these receptors are involved in APOPTOSIS signaling pathways. Several DEATH DOMAIN RECEPTOR SIGNALING ADAPTOR PROTEINS can bind to the death domains of the activated receptors and through a complex series of interactions activate apoptotic mediators such as CASPASES. Death Domain Receptors,Death Receptor,Death Receptors,Receptors, DR Family,Receptors, Death Domain Family,DR Family Receptors,Receptor, Death

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