Disentangling Pro-mitotic Signaling during Cell Cycle Progression using Time-Resolved Single-Cell Imaging.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Cell proliferation is tightly regulated by extracellular growth factors during development and homeostasis.
• Mitogenic signals activate complex, synergistic pathways to control cell cycle progression.
• The precise roles of these pathways, particularly in later cell cycle stages, are not fully understood.

Purpose of the Study:

• To quantify epidermal growth factor (EGF)-induced signaling dynamics in human cells.
• To dissect the time-resolved contribution of downstream signaling pathways to cell cycle progression.
• To identify signaling features encoding information about ligand concentration and cell cycle timing.

Main Methods:

• Quantitative time-resolved measurements using fluorescent reporters in untransformed human cells.
• Targeted pharmacological inhibition of key signaling pathways.
• Statistical analysis to dissect pathway contributions and identify critical signaling features.

Main Results:

• Defined signaling features that encode extracellular ligand concentrations and critical time windows for cell cycle transitions.
• Demonstrated that both extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase (PI3K) activity are essential for initial cell cycle entry.
• Showed that PI3K activity, but not ERK, influences the duration of S phase at later stages of mitogenic signaling.

Conclusions:

• Signaling pathway contributions to cell cycle progression are temporally distinct.
• ERK and PI3K play differential roles in regulating cell cycle entry and S phase duration.
• Understanding these dynamics is crucial for comprehending cell proliferation control.