Expression of calbindin-D28k in C6 glial cells stabilizes intracellular calcium levels and protects against apoptosis induced by calcium ionophore and amyloid beta-peptide.
The calcium binding protein, calbindin-D28k is normally present in neurons. Recently we reported that brain injury and tumor necrosis factors (TNFs) induce calbindin-D28k in astrocytes. TNF-treated calbindin expressing astrocytes were resistant to acidosis and calcium ionophore toxicity, suggesting that calbindin may have a cytoprotective role in astrocytes in the injured brain (M.P. Mattson, B. Cheng, S.A. Baldwin, V.L. Smith-Swintosky, J. Keller, J. Geddes, Scheff, J.W., Christakos, S., Brain injury and tumor necrosis factors induce calbindin-D28k in astrocytes: evidence for a cytoprotective response, J. Neurosci. Res., 42 (1995) 257). In order to obtain direct evidence for a role of calbindin, using the eukaryotic expression vector pREP4, rat calbindin-D28k was stably expressed in C6 rat astocytoma glial cells. Cytotoxicity in response to calcium ionophore or amyloid beta-peptide (which accumulates in the brain in Alzheimer's disease and has been reported to be neurotoxic) was measured by MTT reduction in vector transfected cells and in calbindin transfected clones. Stably expressed calbindin resulted in increased cell survival in the presence of calcium ionophore (1-10 microM) or amyloid beta-peptide (10-100 microM). In addition, the calcium ionophore or amyloid beta-peptide mediated rise in intracellular calcium in vector transfected cells was significantly attenuated in calbindin expressing cells. Apoptotic cell death was detected by the Hoechst method in vector transfected C6 glial cells treated with calcium ionophore or beta-amyloid (34-36% apoptotic cells/culture). The number of apoptotic nuclei was significantly attenuated in similarly treated calbindin-D28k transfected clones (10-13% apoptotic cells/culture; p<0.01). Our results support the involvement of calcium fluxes in apoptosis and suggest that calbindin-D28k, by buffering calcium, can suppress death in apoptosis susceptible cells in the central nervous system.
Wernyj
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RP
Departments of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical and Graduate School of Biomedical Sciences, 185 South Orange Avenue, Newark, NJ 07103-2714, USA.
Mattson
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MP
Christakos
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D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001253:Astrocytes / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D001254:Astrocytoma; D064092:Calbindin 1; D064026:Calbindins; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects; D007476:Ionophores / Q000494:pharmacology*; D008928:Mitochondria / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics; D010641:Phenotype; D010957:Plasmids; D051381:Rats; D064030:S100 Calcium Binding Protein G / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured
D016229:Amyloid beta-Peptides; C576500:Calb1 protein, rat; D064092:Calbindin 1; D064026:Calbindins; D007476:Ionophores; D009419:Nerve Tissue Proteins; D064030:S100 Calcium Binding Protein G; D000001:Calcimycin; D002118:Calcium