[Possible mechanisms of action of growth factors and cell aging].
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.
Romanchikov
Iu M
IuM
D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D005246:Feedback / Q000502:physiology; D006133:Growth Substances / Q000502:physiology*; D008433:Mathematics; D008954:Models, Biological; D009857:Oncogenes / Q000235:genetics; D015290:Second Messenger Systems / Q000502:physiology*
D006133:Growth Substances
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