Stretching transition of vesicles with confined filament loops: Morphological evolution with filament distortion and reorientation

The intricate mechanical interplay between cell membranes and enclosed filaments or filament networks plays an essential role in governing cellular morphological transformations and various cellular activities. A profound understanding of fundamental mechanical mechanisms underlying these interactions can be gained by exploring mechanical behaviors of a filament-vesicle system. Here we theoretically investigate the axial stretching of a lipid vesicle containing an enclosed filament loop. The vesicle either freely adjusts its volume or maintains a fixed volume. Depending on the relative stiffness and size of the filament loop to the vesicle as well as the vesicle scenario, the vesicle prior to stretching exhibits a spherical, prolate or oblate shape, and during stretching it undergoes morphological transformations with pronounced filament distortion and reorientation. The filament-vesicle system could exhibit a spring-softening or -stiffening response during stretching. Moreover, effects of filament inhomogeneity on the stretching process are studied. Our results could serve as a quantitative benchmark for further investigations into cellular complexity.