Biomechanics of budding of cellular membranes

Biomechanics of the cell shape changes and the budding of the cellular membrane is described. It is indicated that two mechanisms based on internal degrees of freedom: in-plane orientational ordering of membrane constituents and non-homogeneous lateral distribution of membrane constituents, are complementary mechanisms that may promote budding of the membrane and determine the shape of the released daughter vesicle (spherical or tubular). Tubular budding may be explained by self-assembly of anisotropic membrane nanodomains into larger domains forming nanotubular membrane protrusions. In contrast to some previously reported theories, no direct external mechanical force is needed to explain the tubular budding of cellular membrane. The mechanism that explains tubular budding may also be responsible for stabilization of tunneling nanotubes (TNT) that connect cells and are important for transport of matter and information in cellular systems.