Inhibition of PKB/Akt1 by C2-ceramide involves activation of ceramide-activated protein phosphatase in PC12 cells.
Accumulation of ceramide has been reported in stress- and receptor-induced apoptosis in the nervous system. However, its role in apoptosis signaling remains elusive. We describe here the inhibition of the NGF-activated phosphoinositide 3-kinase (PI3K)-PKB/Akt1 survival pathway by the cell permeable analog C2-ceramide. C2-ceramide did not inhibit ERK, PI3K, or PDK1 activities and did not alter the translocation of PDK1 and Akt1 to the plasma membrane, but blocked nuclear translocation of Akt1. Down-regulation of the Akt pathway was due to enhanced dephosphorylation of Akt1 at residues T308 and S473. Moreover, Akt1 was dephosphorylated in vitro by a cation-independent phosphatase involving ceramide-activated protein phosphatase (CAPP). Membrane-anchored Akt1 was more resistant to dephosphorylation/inactivation by C2-ceramide than wild-type Akt1. Consistently, N-myristylated-Akt1 conferred resistance to the apoptosis induced by C2-ceramide in PC12 cells. These results provide a novel mechanism for induction of apoptosis by ceramide in nerve-derived cells.
Salinas
M
M
Departamento de Bioquímica, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo, 4 Madrid, 28029, Spain.
López-Valdaliso
R
R
Martín
D
D
Alvarez
A
A
Cuadrado
A
A
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D051379:Mice; D020932:Nerve Growth Factor / Q000494:pharmacology; D016716:PC12 Cells; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014162:Transfection; D000077191:Wortmannin
D000730:Androstadienes; C064769:N-acetylsphingosine; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D020932:Nerve Growth Factor; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D010749:Phosphoprotein Phosphatases; D013110:Sphingosine; D000077191:Wortmannin