Interplay between cortical adhesion and membrane bending regulates microparticle formation

The formation of microparticles requires the bending of the plasma membrane away from the cytosol. The capcity of the cell membrane to form a microparticle, and the rate of membrane deformation, are controlled by multiple factors, including loss of lipid asymmetry (primarily the exposure of phosphatidylserine on the outer leaflet), detachment of the membrane from the cortical cytoskeleton, and bleb expansion due to pressure. In this work, we develop a biophysical model that accounts for the interaction between these different factors. Our findings reveal that the linkage between the membrane and cortex is a key determinant of outward budding. Ultimately, the rates and mechanical parameters regulating cortical linkage interact with the kinetics of phosphatidylserine flipping, laying out a mechanical phase space for regulating the outward budding of the plasma membrane.