Insulin stimulation of high frequency phosphorylation dynamics in murine erythroleukemia cells

The phosphorylation potentials of two proteins (M(r) 81 kDa and 63 kDa) in extracts of murine erythroleukemic (MEL) cells both vary in an oscillatory manner, sometimes changing by as much as 100-fold in 10 min. Direct analysis of the temporal changes indicates the existence of periodic modulation of the frequencies, amplitudes and mean levels of the two rhythms. In both cases, periodogram analyses, by two methods, confirm the presence of several oscillations having periods in the range 20-100 min which tend to occur in (pseudo) periodic bursts. Insulin has been found to enhance these oscillations in a manner comparable with its effect on rhythmic variations in cell morphology. Despite the marked similarity in the behaviour of the two proteins, no particular phase relationship existed between the two temporal variations, suggesting differences between the underlying driving forces.