epidermal-growth-factor and ceramide-1-phosphate

Ceramide-1-phosphate (C1P) is emerging as a new addition to the family of bioactive sphingolipid metabolites. At low concentrations, C1P enhanced survival of NIH 3T3 fibroblasts and A549 lung cancer cells, while at high concentrations, it reduced survival and induced apoptosis. Apoptosis correlated with degradation of C1P to pro-apoptotic ceramide. To examine the role of endogenous C1P, expression of ceramide kinase, the enzyme that produces C1P, was downregulated, which reduced cellular proliferation, progression into S phase and enhanced apoptosis induced by serum starvation. Our results suggest that ceramide kinase determines the balance between pro-apoptotic ceramide and anti-apoptotic C1P to regulate cell fate, reminiscent of its function in plants.

Topics: Adenocarcinoma; Animals; Apoptosis; Cattle; Cell Cycle; Cell Proliferation; Cell Survival; Ceramides; Down-Regulation; Epidermal Growth Factor; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Mice; NIH 3T3 Cells; Phosphotransferases (Alcohol Group Acceptor); RNA, Messenger; RNA, Small Interfering

We found that natural (long-chain) ceramide 1-phosphate can be dispersed into aqueous solution when dissolved in an appropriate mixture of methanol/dodecane (49:1, v/v). This solvent mixture facilitates the interaction of this phosphosphingolipid with cells. Under these conditions, incubation of EGFR T17 fibroblasts with natural ceramide 1-phosphate caused a potent stimulation of DNA synthesis. This effect was accompanied by an increase in the levels of proliferating-cell nuclear antigen. Concentrations of natural ceramide 1-phosphate that stimulated the synthesis of DNA did not inhibit adenylate cyclase activity, nor did they stimulate phospholipase D. Natural ceramide 1-phosphate did not alter the cellular phosphorylation state of tyrosine residues or of mitogen-activated protein kinase. Furthermore, natural ceramide 1-phosphate failed to induce the expression of the proto-oncogenes c-myc and c-fos. Both the stimulation of DNA synthesis and the induction of proliferating-cell nuclear antigen by natural ceramide 1-phosphate were inhibited by natural ceramides. This work suggests that the use of methanol and dodecane to deliver natural ceramide 1-phosphate to cells may be useful for elucidation of the biological function(s) and mechanism(s) of action of ceramide 1-phosphate.

Topics: 3T3 Cells; Animals; Blotting, Northern; Blotting, Western; Calcium-Calmodulin-Dependent Protein Kinases; Ceramides; DNA; Epidermal Growth Factor; Gene Expression Regulation; Genes, fos; Genes, myc; Mice; Phosphorylation; Proliferating Cell Nuclear Antigen