  Eukaryotic cells adhere to extracellular matrix during the normal development
of the organism, forming static adhesion as well as during cell motility. We
study this process by considering a simplified coarse-grained model of a
vesicle that has uniform adhesion energy with a flat substrate, mobile curved
membrane proteins and active forces. We find that a high concentration of
curved proteins alone increases the spreading of the vesicle, by the
self-organization of the curved proteins at the high curvature
vesicle-substrate contact line, thereby reducing the bending energy penalty at
the vesicle rim. This is most significant in the regime of low bare
vesicle-substrate adhesion. When these curved proteins induce protrusive
forces, representing the actin cytoskeleton, we find efficient spreading, in
the form of sheet-like lamellipodia. Finally, the same mechanism of spreading
is found to include a minimal set of ingredients needed to give rise to motile
phenotypes.
