Modeling cellular shape changes in the presence of curved membrane proteins and active cytoskeletal forces

Cell shape can dynamically change to accommodate a variety of tasks. One mechanism for deforming the cellular membrane into the desired shape is through the use of curved membrane proteins (CMP). These proteins are often associated with the recruitment of the cytoskeleton, which then applies active forces that reshape the membrane, forming buds, necks, ruffles, or protrusions. In this review, we present the results of a simplified coarse-grained model of a vesicle with mobile CMP and active protrusive forces. We present the phase space of solutions for the passive and active force cases and find distinct classes of shapes: uniform, isolated buds, long finger-like protrusions, and pancake-like with proteins aggregated at the rim. The model is finally complemented with an inclusion of a uniform adhesion energy with a flat substrate, revealing that when curved proteins induce protrusive forces, a mechanism of efficient spreading is possible in the form of sheet-like lamellipodia, constituting a minimal system underlying cell motility.