Fig 2: Prediction of the Impact of Growth Factor on Cell-to-Cell Variability(A) Evolution of the inferred distributions of the total amount of phosphorylated ERK and MEK in response to stimulation by EGF with two levels of intensity. The hyper-parameters for the initial conditions and the reaction rates are fixed to the previously estimated values (using the single-cell data in response to NGF stimulus), whereas the hyper-parameters describing the impact of the stimulus and upstream signals on the kinase are inferred here separately. The single-cell data distributions (boxplots) are compared to the inferred distributions (the lines represent the median of the distributions, while the shaded regions indicate the regions delimited by 5th and 95th percentiles for the lighter regions and the one delimited by 25th and 75th percentiles for the darker regions).(B) The predictions for the behavior of the total amount of phosphorylated ERK and MEK under the extrinsic noise model (left columns) are compared to experimental measurements (right columns) for different level of NGF intensity. The solid lines indicate the median value, while the shaded regions indicate the regions delimited by 5th and 95th percentiles (lighter zones) and by 25th and 75th percentiles (darker zones).

Fig 3: ERK inhibits PPARa during the refed state. (A) Schematic diagram of experimental design where overnight fasted and refed (fasted overnight and then refed) mice that were treated with vehicle or GSK (3 mg/kg body weight). (B) qPCR analysis of PPARa target genes in the livers of fasted and refed mice treated with or without GSK. (C) Liver and (D) serum triglycerides measured in the fasted and refed mice. Bar graphs are presented as mean standard error ± standard error of the mean. *P < .05, **P < .01 as analyzed by two-tailed Student t test. RF, refed.

Fig 4: Evolutionary analysis of EREG binding to LepR. (A–E) EREG docking to LepR. Evolutionary analysis of 175 open The dependence of EREG-mediated glucose uptake on the ERK phosphorylation cascade was examined using (1) a specific inhibitor of ERK1/2 SCH772984 [56], (2) an inhibitor of ERK dimerization DEL-22379 [57], and (3) a selective inhibitor of MEK1 and MEK2 U0126 [58]. All inhibitors increased basal glucose uptake, which was further increased by leptin (Figure 4F). The inhibition of ERK1/2 and MEK1/2 as well as ERK dimerization prevented stimulatory effect of EREG on FD-glucose uptake but did not decrease it beyond the levels seen in the control cells. Although transient ERK phosphorylation occurred in response to EREG stimulation, this pathway was dispensable for glucose uptake and dependent on PI3K and may be other pathways (Figure 4B and Figure S7B). (F) Hypothetic mechanism suggesting EREG as an alternative ligand for both EGFR and LepR. The canonic leptin/LepR response can induce JAK/STAT3 signaling and required the long form of LepR. The alternative binding of EREG to LepR can induce ERK and PI3K activation increasing GLUT4 translocation and glucose uptake, but not the other canonic effects of leptin, including the regulation of appetite and energy expenditure.

Fig 5: A proposed mechanism of signaling pathways that PLL activates in 3T3-L1 adipogenesis. Three essential adipogenic components such as insulin, IBMX, and DEX activate insulin signaling pathway (a), cAMP signaling pathway (b), and glucocorticoid receptor signaling pathway (c) respectively. PLL phosphorylates IR and also activates ERK and AKT indirectly. PLL increases phosphorylation of CREB, indicating the involvement of cAMP pathway. Dotted lines indicate an ambiguous mechanism that was influenced by PLL