Inhibition of CTP:phosphocholine cytidylyltransferase by C(2)-ceramide and its relationship to apoptosis.
Apoptosis induced by antitumor phospholipid analogs takes place after the inhibition of the CTP:phosphocholine cytidylyltransferase (CCT; EC 2.7.7.15) catalyzed step of phosphatidylcholine (PtdCho) biosynthesis. Exposure of cells to synthetic short-chain ceramide analogs also triggers apoptosis concomitant with decreased PtdCho biosynthesis, and the present study was undertaken to ascertain whether C(2)-ceramide inhibition of PtdCho synthesis is direct or secondary to other ceramide-mediated cellular responses. The exposure of COS-7 cells to either C(2)-ceramide, ET-18-OCH(3), or farnesol resulted in time- and dose-dependent apoptotic cell death. Cells treated with C(2)-ceramide or ET-18-OCH(3) selectively and immediately accumulated phosphocholine, whereas CDP-choline increased with farnesol treatment. In vitro assays of CCT activity demonstrated that C(2)-ceramide directly inhibited CCT. Comparison of different N-linked sphingosine derivatives suggests an inverse relationship between the length of the N-linked carbon chain and the derivatives ability to trigger apoptosis and inhibit CCT. Taken together, our results suggest CCT as a primary target for C(2)-ceramide inhibition that accounts for its cytotoxic effects.
Ramos
Belén
B
Departamento de Fisiología, Universidad de Extremadura, Cáceres, Spain.
El Mouedden
Mohammed
M
Claro
Enrique
E
Jackowski
Suzanne
S
D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D019916:Choline-Phosphate Cytidylyltransferase / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D000882:Haplorhini; D008854:Microscopy, Electron; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology*
D004791:Enzyme Inhibitors; C064769:N-acetylsphingosine; D019916:Choline-Phosphate Cytidylyltransferase; D013110:Sphingosine