Integrin-mediated signalling through the MAP-kinase pathway
The mitogen activated protein (MAP) kinase cascade, leading to extracellular-regulated kinase (ERK) activation, is a key regulator of cell growth and proliferation. The effects of ERK are mediated by differences in ERK signalling dynamics, including magnitude and duration. In vivo, ERK signalling is stimulated by both growth factors and adhesion signals. A model for adhesionmediated ERK activation is presented. Outputs of the model such as ERK and FAK activation, as well as responses to different ligand densities, are compared with published experimental data. The model then serves as a basis for understanding how adhesion may contribute to ERK signalling through changes in the dynamics of focal adhesion kinase activation. The main parameters influencing ERK are determined through screening analyses and parameter variation. With these parameters, key points in the pathway that give rise to changes in downstream signalling dynamics are identified. In particular, oncogenic Raf and Ras promote cell growth by increasing the magnitude and duration, respectively, of ERK activity.