title: Production of homocysteine in serum-starved apoptotic PC12 cells depends on the activation and modification of Ras.
abstract: PC12 pheochromocytoma cells expressing a dominant inhibitory mutant of Ha-Ras (M-M17-26) and PC12 cells transfected with normal c-RasH (M-CR3B) have been used to investigate the role of nitrosylation and farnesylation of Ras on the production of homocysteine and the activities of the redox-sensitive transcription factors NF-kappaB and c-Fos. We found that under serum and nerve growth factor withdrawal conditions undifferentiated apoptotic M-CR3B cells accumulated more homocysteine than M-M17-26 cells, and the production of homocysteine decreased in the presence of manumycin and increased in the presence of l-NAME. Furthermore, we have shown that manumycin increased the activity of c-Fos in the M-CR3B cells and decreased the activity of NF-kappaB, while l-NAME decreased the activities of both transcription factors, and accelerated apoptosis of M-CR3B cells. In contrast, in M-M17-26 cells manumycin did not change the activity of c-Fos, nor the activity of NF-kappaB. We conclude that trophic factor withdrawal stimulates Ras, which apparently through the Rac/NADPH oxidase system induces permanent oxidative stress, modulates the activities of NF-kappaB and c-Fos, induces production of homocysteine and accelerates apoptosis. Nitrosylation of Ras is necessary for maintaining the survival of PC12 cells, while farnesylation of Ras stimulates apoptosis under withdrawal conditions.
authors.affiliation: Institute of Physiology, Georgian Academy of Sciences, Tbilisi, Georgia.
authors.forename: T
authors.initials: T
authors.lastname: Barbakadze
authors.forename: E
authors.initials: E
authors.lastname: Zhuravliova
authors.forename: M
authors.initials: M
authors.lastname: Sepashvili
authors.forename: E
authors.initials: E
authors.lastname: Zaalishvili
authors.forename: J J
authors.initials: JJ
authors.lastname: Ramsden
authors.forename: J
authors.initials: J
authors.lastname: Bátor
authors.forename: J
authors.initials: J
authors.lastname: Szeberényi
authors.forename: D
authors.initials: D
authors.lastname: Mikeladze
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D016895:Culture Media, Serum-Free; D006710:Homocysteine / Q000096:biosynthesis*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D016716:PC12 Cells; D017368:Protein Prenylation / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016895:Culture Media, Serum-Free; D016328:NF-kappa B; D016760:Proto-Oncogene Proteins c-fos; D006710:Homocysteine; D018631:ras Proteins