Survival and cell death in cells constitutively unable to synthesize glutathione.
We examined the role of GSH in survival and cell death using GCS-2 cells that are deficient in glutamate cysteine ligase (gamma-glutamyl cysteine synthetase, gammaGCS), an enzyme essential for GSH synthesis. Cells maintained in 2.5 mM GSH have GSH levels that are approximately 2% of wild type and grow indefinitely; however, they express both pro- and anti-apoptotic Bcl-2 family members and have detectable levels of cytoplasmic cytochrome C. Withdrawal of GSH from the medium results in a fall in intracellular GSH to undetectable levels, decreased mitochondrial dehydrogenase activity, decreased anti-apoptotic factor RNAs, increased pro-apoptotic factor RNAs, additional cytochrome C release, and a fall in ATP levels; however, cells continue to grow for another 24h. At 48 h, these trends continue with the exception that mitochondrial membrane potential and ATP levels rise; DNA fragmentation begins at 48 h. Thus, severe reduction of GSH to 2% of wild type produces a metastable state compatible with survival, but complete absence of GSH triggers apoptosis.
Valverde
Mahara
M
Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Rojas
Emilio
E
Kala
Subbarao V
SV
Kala
Geeta
G
Lieberman
Michael W
MW
D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D017077:Culture Media, Conditioned; D045304:Cytochromes c / Q000378:metabolism; D005721:Glutamate-Cysteine Ligase / Q000172:deficiency* / Q000235:genetics; D005978:Glutathione / Q000096:biosynthesis / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics
D017077:Culture Media, Conditioned; D019253:Proto-Oncogene Proteins c-bcl-2; D045304:Cytochromes c; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione