Silja Borring Låstad

Active flow and friction in cells

Mechanobiology is an important interdisciplinary field focusing on the interplay between cellular biology and mechanical entities like force, flow and elasticity. Central to the biological viewpoint is the concept of mechanotransduction: how cells convert mechanical stimuli into electrochemical activity. An example of such mechanical stimulus is the elasticity and adhesion of the extracellular matrix (ECM) that the cell attaches to. Biological research on mechanotransduction tends to focus on the sensing proteins, the signal molecules and changes in gene expression. Physics research on mechanotransduction focuses on physical modelling the active cytoskeleton, mechanical properties of the ECM and adhesion interactions between the two. These models normally explore how much of the cellular behaviour can be described without invoking changes in behaviour due to genetic expressions introducing new proteins.

This thesis will continue in this tradition of physical models and focus on
two problems. One project will probe a long-standing debate in cell migration, which is the oldest field in mechanobiology: Should the nature of actin-ECM adhesion be modelled as a non-linear, space-dependent or non-local friction in continuum, active gel models? This project will use ECM elasticity as the physical parameter that influences cell behaviour. The other project is novel in the sense that physical models of the process do not yet exist: Why does the shape of the adhesive region where a cell is attached, affect the actin dynamics during macropinocytosis.