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Title: c-Jun is a downstream target for ceramide-activated protein phosphatase in A431 cells
Authors: Reyes, Juan González
Robayna, Ignacio González 
Delgado, Pino Santana 
González, Inmaculada Hernández 
Aguiar, José Quintana 
Estévez Rosas, F. 
Fanjul, Luisa F. 
Ruiz de Galarreta, C. M.
UNESCO Clasification: 32 Ciencias médicas
2302 Bioquímica
Keywords: Tumor-Necrosis-Factor
Sphingolipid Breakdown Products
Factor-Alpha, et al
Issue Date: 1996
Journal: Journal of Biological Chemistry 
Abstract: Stimulation of [H-3]serine-labeled A431 cells with tumor necrosis factor-alpha (TNF alpha) or bacterial sphingomyelinase (SMase) resulted in a rapid decrease (similar to 50% by 15 min) in cellular [H-3]sphingomyelin content and generation of the lipid moiety [H-3]ceramide, which remained elevated 60 min later, Sphingomyelin hydrolysis in response to TNF alpha or bacterial SMase resulted in a time-dependent decrease in the phosphorylation state of c-Jun protein, an effect that was also observed in cells treated with the membrane-permeable ceramide analogue N-hexanoylsphingosine (C-6-ceramide). The rapid dephosphorylation of the c-Jun gene product in response to TNF alpha, SMase, or C-6-ceramide was not observed in A431 cells treated with the serine-threonine phosphatase inhibitor okadaic acid. After the initial steps of previously described methods for the purification of a ceramide-activated protein phosphatase termed CAPP (Dobrowsky, R, T., Kamibayashi, C,, Mumby, M, C., and Hannun, Y. A, (1993) J, Biol, Chen. 268, 15523-15530), we obtained a cytosolic fraction from A431 cells that specifically dephosphorylated P-32(i)-labeled c-Jun protein used as substrate in an immunocomplex phosphatase assay, Phosphatase activity in vitro was apparent only in the presence of ceramide (5 mu m) and was specifically abrogated when okadaic acid (1 nM) was included in the immunocomplex phosphatase assay, These results provide strong evidence for c-Jun as a downstream target for CAPP activated in response to post-TNF signaling in A431 cells.
ISSN: 0021-9258
DOI: 10.1074/jbc.271.35.21375
Source: Journal Of Biological Chemistry[ISSN 0021-9258],v. 271 (35), p. 21375-21380 (Septiembre 199
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