13C-NMR investigation of protein synthesis during apoptosis in human leukemic cell lines

In order to evaluate the role of protein synthesis in apoptosis, (13)C-NMR has been used to study the levels of protein synthesis in three different human leukemic cell lines in the presence and absence of dexamethasone-induced apoptosis. Measurements were done on one dexamethasone-sensitive (CEM-C7-14) and two different dexamethasone-resistant variants (CEM-4R4 and CEM-ICR27-4). The incorporation of (13)C-labeled amino acids into cellular proteins, which reflects the level of new protein synthesis, was monitored by (13)C-NMR spectroscopy. In the absence of dexamethasone, the level of protein synthesis was found to be significantly different among the three cell lines. Dexamethasone caused a significant reduction ( congruent with 60-87%) in the level of protein synthesis in dexamethasone-sensitive CEM-C7-14 cells, while having no significant effect on protein synthesis in dexamethasone-resistant CEM-4R4 cells. Dexamethasone treatment caused a significant enhancement of the level of protein synthesis in the CEM-ICR27-4 cells. Synthesis of proteins was found to occur during apoptosis, albeit at a low level, suggesting a role for the synthesis of specific proteins in the mechanism of apoptosis.