Stimulation of fructose 1,6‐bisphosphate production in melanoma cells by α‐melanocyte‐stimulating hormone

Abstract

In a 31 P-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 [Ahx 4 , DPhe 7 ]A-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, 1506Ϫ 1510. Chemical identification of these metabolites was performed in this study using 32 P metabolic labeling and polyethyleneimine-cellulose thin layer chromatography in combination with 31 P-NMR and 13C-NMR spectroscopic methods. Two of the stimulated signals were identified as P 1 and P 6 of fructose 1,6-bisphosphate (FruP 2 ) and their mode of regulation by A-melanotropin was examined. The FruP 2 response to A-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 FruP 2. The stimulatory effect of A-melanotropin was not associated with a change in the overall rate of glycolysis, suggesting that FruP 2 levels were not rate limiting in this process. The data suggest the presence of a previously unknown response of M2R melanoma cells to A-melanotropin, which coincides in time with enhanced cAMP accumulation but is not mediated by cAMP and may relate to the control of FruP 2 in a non glycolytic context.Keywords : cAMP ; fructose 1,6-bisphosphate; melanoma ; A-melanotropin; NMR.A-melanotropin controls the synthesis of melanin in melanocytes by cAMP-mediated regulation of the levels and activity of tyrosinase, the rate-limiting enzyme in melanin synthesis [1Ϫ 4]. The cAMP response of M2R mouse melanoma cells to Amelanotropin has been previously studied in our laboratory [5Ϫ 7]. Stimulation of the cells by A-melanotropin and a low synergistic dose of forskolin, in the presence of isobutylmethylxanthine (iBuMeXan), resulted in an unusually high cAMP response; nearly 50% of the cellular [ 3 H]adenine was converted into [ 3 H]cAMP [5]. This phenomenon was further delineated by 31 P-NMR spectroscopy of cultured M2R cells, which showed that A-melanotropin stimulation under these conditions indeed elevated cellular cAMP to sub-millimolar concentrations coinciCorrespondence to Y. Salomon,

Glycolysis as a metabolic marker in orthotopic breast cancer, monitored by in vivo 13C MRS

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Structural and Functional Characterization of YdjI, an Aldolase of Unknown Specificity in Escherichia coli K12

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“…(d)31 P NMR spectrum of FBP obtained commercially. Peak assignments for FBP obtained from previously published reports 44,45.…”

MtnK, methylthioribose kinase, is a starvation-induced protein in Bacillus subtilis

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