Disentangling Pro-mitotic Signaling during Cell Cycle Progression using Time-Resolved Single-Cell Imaging
Manuela Benary1, Stefan Bohn2, Mareen Lüthen3
1Institute of Pathology, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany; Institute for Theoretical Biology, Charité-Universitätsmedizin Berlin, 10115 Berlin, Germany; Integrative Research Institute Life Sciences, Humboldt University Berlin, 10115 Berlin, Germany.
Abstract:
Cells rely on input from extracellular growth factors to control their proliferation during development and adult homeostasis. Such mitogenic inputs are transmitted through multiple signaling pathways that synergize to precisely regulate cell cycle entry and progression. Although the architecture of these signaling networks has been characterized in molecular detail, their relative contribution, especially at later cell cycle stages, remains largely unexplored. By combining quantitative time-resolved measurements of fluorescent reporters in untransformed human cells with targeted pharmacological inhibitors and statistical analysis, we quantify epidermal growth factor (EGF)-induced signal processing in individual cells over time and dissect the dynamic contribution of downstream pathways. We define signaling features that encode information about extracellular ligand concentrations and critical time windows for inducing cell cycle transitions. We show that both extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase (PI3K) activity are necessary for initial cell cycle entry, whereas only PI3K affects the duration of S phase at later stages of mitogenic signaling.
Insights
This study reveals how cells process growth factor signals to divide. Both ERK and PI3K pathways are crucial for cell cycle entry, with PI3K also regulating later S phase duration.
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.
