p38 MAPK and the C2C12 cell cycle : in vitro and in silico investigations.

Abstract

The mammalian cell cycle and its points-of-entry are well characterized pathways. These points-of-entry are normally regulated via mitogens and include, amongst others, the ERK, JNK and p38 mitogen-activated protein kinase (MAPK) pathways. However, while the restriction point(R-point), the temporal switch-point at which a cell becomes irrevocably committed to division irrespective of mitogenic stimulus, is known among other cell types, its position within the murine myoblast line C2C12 is currently unknown. Similarly, while MAPK pathways, such as JNK and ERK, have been modeled computationally, no model yet exists of p38 MAPK as stimulated by mitogens. The aims of this dissertation, then, were to determine the R-point within the C2C12 cell cycle and construct a computational mitogen-stimulated p38 MAPK model. It was found that a synchronous C2C12 population, when stimulated to divide, took 7 to 9 hours to reach S-phase from G0, consistent with data from the literature. The R-point was determined to lie between 6 and 7 hours post G1-re-entry stimulation,which was consistent with studies in other cell types. Core modeling of the p38 MAPK pathway revealed that ultrasensitivitywas inherent within the pathway structure. Further, a branching/re-converging structure within the pathway imparted greater responsiveness to signal upon the pathway. A realistic p38 MAPK model demonstrated good responsiveness to signal, its output matched that of several other MAPK models, and it was capable of replicating previous in vitro data. This model can be used as a tool for further investigation of the mammalian cell cycle by linking it to other cell cycle models. The predictions by an expanded model may be better suited for understanding the effects of mitogen stimulus on the cell cycle in situ.