Stimulation of fructose 1,6-bisphosphate production in melanoma cells by alpha-melanocyte-stimulating hormone-- 31P/13C-NMR and 32P-labeling studies.

In a 31P-NMR spectroscopic study of cultured M2R mouse melanoma cells, we previously demonstrated the acute stimulation of three peaks in the phosphomonoester region of the spectrum by [Ahx4, DPhe7]alpha-melanotropin (concomitant with an increase in cellular adenosine 3',5'-phosphate (cAMP) and a decrease in ATP [Degani, H., DeJordy, J. O. & Salomon, Y. (1991) Proc. Natl Acad. Sci. USA 88, 1506-1510]. Chemical identification of these metabolites was performed in this study using 32P metabolic labeling and polyethyleneimine-cellulose thin layer chromatography in combination with 31P-NMR and 13C-NMR spectroscopic methods. Two of the stimulated signals were identified as P1 and P6 of fructose 1,6-bisphosphate (FruP2) and their mode of regulation by alpha-melanotropin was examined. The FruP2 response to alpha-melanotropin coincided in time and dose with a rise in cAMP and a decrease in levels of ATP, while elevation of cAMP by forskolin alone did not increase FruP2. The stimulatory effect of alpha-melanotropin was not associated with a change in the overall rate of glycolysis, suggesting that FruP2 levels were not rate limiting in this process. The data suggest the presence of a previously unknown response of M2R melanoma cells to alpha-melanotropin, which coincides in time with enhanced cAMP accumulation but is not mediated by cAMP and may relate to the control of FruP2 in a non glycolytic context.