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[Possible mechanisms of action of growth factors and cell aging]
Abstract:
Main effects of growth factors (GFs) on proliferation seem to be mediated by second messengers (SMs). A variety of feed-backs in the SM system allows to suggest that cell cycling is determined by self-oscillations of levels of the SMs and SM-dependent proteins. GFs perform roles of parameter switches of the system functioning regimes; self-oscillations occur only if the GF levels are within certain range. This approach makes it possible to explain the GF synergy, dual roles of GFs as activators and inhibitors of proliferation, and cell cycle duration variability. It predicts that GFs must accelerate some cell cycle phases and decelerate other phase. When the GF levels are sharply changed, cells may become terminally differentiated, which allows to explain a limited number of cell divisions in culture. We can also explain why some oncogenes decrease the dependence of cells on GFs but cells undergo a limited number of divisions, and other oncogenes enable cells to divide unlimitedly.
Insights
Growth factors (GFs) regulate cell proliferation via second messengers (SMs) and self-oscillating systems. This model explains GF synergy, dual roles, and cell division limits, impacting cancer research.
Area of Science:
- Cell biology
- Biophysics
- Biochemistry
Background:
- Growth factors (GFs) are crucial for cell proliferation.
- The precise mechanisms by which GFs regulate cell cycling, especially their synergistic and dual roles, remain complex.
- Second messengers (SMs) are known to mediate GF signaling pathways.
Purpose of the Study:
- To elucidate the role of second messengers (SMs) in mediating growth factor (GF) effects on cell proliferation.
- To propose a model where cell cycling is governed by self-oscillations within the SM system.
- To explain GF synergy, dual roles, and cell division variability using this proposed model.
Main Methods:
- Theoretical modeling of second messenger (SM) system dynamics.
- Analysis of feedback mechanisms within the SM network.
- Simulation of cell cycle regulation under varying growth factor (GF) levels.
Main Results:
- GFs act as parameter switches for the SM system, influencing self-oscillations.
- Self-oscillations in SM levels and SM-dependent proteins determine cell cycling.
- GF levels within a specific range are necessary for self-oscillations, explaining GF synergy and dual roles.
- The model predicts differential acceleration and deceleration of cell cycle phases by GFs.
- Abrupt GF level changes can induce terminal differentiation, limiting cell divisions.
- The model accounts for oncogene-mediated GF independence and limited proliferation.
Conclusions:
- Cell proliferation is regulated by self-oscillating dynamics of second messengers (SMs) modulated by growth factors (GFs).
- This model provides a unified explanation for various observed phenomena in cell cycle regulation, including GF synergy and differentiation.
- The findings offer insights into the mechanisms underlying uncontrolled cell division in cancer and the limited lifespan of cultured cells.