Cell-matrix adhesive structures as localized self-sustained objects in a diffusion-reaction model

Integrin receptors mediate interaction between cells and extracellular matrix. These receptors do not possess any catalytic properties by themselves and must recruit additional signaling molecules upon activation to transmit signal to the cell (outside-in signaling). Additionally, integrin activation is achieved by diffusing cytoplasmic partners (inside-out signaling). Using these two properties, we construct a reaction diffusion model based on a two-states model for integrin receptors. Our model takes into account integrin diffusion, and it describes cell adhesive structures as static and dynamic localized self-sustained adhesive objects. The properties of these structures are shown to depend mainly on kinetic parameters (time scale and diffusion lengths) It is shown that integrin diffusion promotes granulation of space into spots of adhesive structures for a wide range of parameters. We discuss this model in the context of adhesive structures podosome type that are the hallmarks of invasive cells. We propose that the different modes of self-organization of podosomes are fundamentally the same process related to integrin activation amplified by a positive feedback loop due to a kinase activation.