Figure 6.
Fourier transform-based analysis helps crack a distinct ERK1/2 activity code in necroptosis in L929 cells
(A) Fourier analysis of the ERK1/2 oscillations extracted from raw FRET/CFP ratio data of Figure 4. For each condition described in Figure 4, the corresponding power spectral density (PSD) for each frequency (106) is displayed by a kymographic representation (from 1h to 15h after the beginning of imaging) in which each row represents one cell. Lower (0.000018 Hz) and higher (0.002 Hz) frequencies are indicated in blue (left) and red (right), respectively. Color-coded LUT denotes the amplitude of PSD (−5 to +35) for each frequency.
(B) For each condition, averaged data are represented where the mean PSD amplitude is plotted against frequency.
(C) For each frequency range (Low (L) f < 5 × 10−5 Hz; Medium (M); High (H) f > 6 × 10−4 Hz frequencies), the mean PSD amplitude (mean ± SEM) for each biological condition is compared.
(D) Fourier analysis of the ERK1/2 oscillations extracted from FRET/CFP ratio data was then performed on three temporal frames with a 2h time-interval for each condition: 1h–3h, 3h–5h, and 5h–7h (from left to right).
(E) For each temporal frame and for each frequency range (Low (L) f < 5 × 10−5 Hz; Medium (M); High (H) f > 6 × 10−4 Hz frequencies), and the mean PSD amplitude (mean ± SEM) for each biological condition is displayed. Grey color on the kymographs.
(F) For each frequency range (Low (L) f < 5 × 10−5 Hz; Medium (M); High (H) f > 6 × 10−4 Hz frequencies), the mean PSD amplitude (mean ± SEM) for each biological condition is compared. Lower (0.00013 Hz) and higher (0.002 Hz) frequencies are indicated in blue (left) and red (right), respectively. Statistical significance was determined using two-way ANOVA followed by Tukey’s post hoc test. Significance between samples is indicated as follows: ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001; ∗∗∗∗p < 0.0001; ns, not significant.