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Xu J, Song D, Xue Z, Gu L, Hertz L, Peng L. Requirement of Glycogenolysis for Uptake of Increased Extracellular K+ in Astrocytes: Potential Implications for K+ Homeostasis and Glycogen Usage in Brain. Neurochem Res 2012; 38:472-85. [DOI: 10.1007/s11064-012-0938-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/09/2012] [Accepted: 11/20/2012] [Indexed: 11/29/2022]
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Dallaporta B, Hirsch T, Susin SA, Zamzami N, Larochette N, Brenner C, Marzo I, Kroemer G. Potassium Leakage During the Apoptotic Degradation Phase. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.11.5605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
The subcellular compartmentalization of ions is perturbed during the process of apoptosis. In this work, we investigated the impact of K+ on the apoptotic process in thymocytes and T cell hybridoma cells. Irrespective of the death-inducing stimulus (glucocorticoids, topoisomerase inhibition, or Fas-crosslinking), a significant K+ outflow was observed during apoptosis, as determined on the single-cell level by means of the K+-sensitive fluorochrome, benzofuran isophtalate. This loss of cytosolic K+ only occurs in cells that have completely disrupted their inner mitochondrial transmembrane potential. Inhibition of this mitochondrial transmembrane potential loss by Bcl-2 or by specific inhibitors acting on the mitochondrial permeability transition pore (bongkrekic acid, cyclosporin A) prevents K+ leakage. K+ drops at the same stage at which cells expose phosphatidylserine residues on the outer leaflet of the membrane and reduce the levels of nonoxidized glutathione, but before they hyperproduce reactive oxygen species, undergo massive Ca2+ influx, shrink, and lyse. In a cell-free system of apoptosis, isolated nuclei exposed to the supernatant of mitochondria that have undergone permeability transition only manifest chromatinolysis when the K+ concentration is lowered from physiologic to apoptotic levels. Accordingly, massive DNA fragmentation causing subdiploidy is confined to cells that have undergone K+ leakage. Together, these data point to the step-wise acquisition of membrane dysfunction in apoptosis and indicate an important role for the disruption of normal K+ homeostasis in apoptotic degradation. Derepression of endonucleases due to low K+ concentrations may be a decisive prerequisite for end-stage DNA fragmentation.
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Affiliation(s)
| | - Tamara Hirsch
- Centre National de Recherche Scientifique, Villejuif, France
| | - Santos A. Susin
- Centre National de Recherche Scientifique, Villejuif, France
| | - Naoufal Zamzami
- Centre National de Recherche Scientifique, Villejuif, France
| | | | | | - Isabel Marzo
- Centre National de Recherche Scientifique, Villejuif, France
| | - Guido Kroemer
- Centre National de Recherche Scientifique, Villejuif, France
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