Abstract |
T-type Ca(2+) channel inhibitors protect hippocampal CA1 neurons from delayed death after global ischemia in rats, suggesting that Cav3.1, Cav3.2, or Cav3.3 channels generate cytotoxic Ca(2+) elevations during anoxia. To test this hypothesis, we measured the Ca(2+) concentration changes evoked by oxygen and glucose deprivation (OGD) in the cytosol and in the mitochondria of PC12 cells. OGD evoked long-lasting cytosolic Ca(2+) elevations that were reduced by Cav3.2 inhibition (50 μm Ni(2+)) and Cav3.1/Cav3.2 silencing and potentiated by Cav3.2 overexpression. The kinetics of the sustained cytosolic Ca(2+) elevations occurring during OGD directly correlated to the extent of cell death measured 20 h after reoxygenation, which was decreased by Ni(2+) and Cav3.1/Cav3.2 silencing and increased by Cav3.2 overexpression. Ni(2+) and Cav3.1/Cav3.2 silencing delayed the decline of cellular ATP during OGD, consistent with a reduction in the Ca(2+) load actively extruded by plasma membrane Ca(2+) pumps. The cytosolic Ca(2+) elevations were paralleled by mitochondrial Ca(2+) elevations that were also increased by Cav3.2 overexpression and decreased by Ni(2+) but not by Cav3.1/Cav3.2 silencing. Overexpression and silencing of the mitochondrial Ca(2+) uniporter, the major mitochondrial Ca(2+) uptake protein, revealed that the cytotoxicity was correlated to the amplitude of the mitochondrial, rather than the cytosolic, Ca(2+) elevations. Selective activation of T-type Ca(2+) channels evoked both cytosolic and mitochondrial Ca(2+) elevations, but only the mitochondrial responses were reduced by Cav3.1/Cav3.2 silencing. We conclude that the opening of Cav3.2 channels during ischemia contribute to the entry of Ca(2+) ions that are transmitted to mitochondria, resulting in a deleterious mitochondrial Ca(2+) overload.
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Authors | Yves Gouriou, Philippe Bijlenga, Nicolas Demaurex |
Journal | The Journal of biological chemistry
(J Biol Chem)
Vol. 288
Issue 18
Pg. 12459-68
(May 03 2013)
ISSN: 1083-351X [Electronic] United States |
PMID | 23508951
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Cacna1g protein, rat
- Cacna1h protein, rat
- Calcium Channels, T-Type
- Adenosine Triphosphate
- Calcium
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Topics |
- Adenosine Triphosphate
(genetics, metabolism)
- Animals
- Calcium
(metabolism)
- Calcium Channels, T-Type
(genetics, metabolism)
- Cell Hypoxia
- Cell Membrane
(genetics, metabolism)
- Cytoplasm
(genetics, metabolism)
- Gene Silencing
- Mitochondria
(genetics, metabolism)
- PC12 Cells
- Rats
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