Active Intracellular Trafficking Dynamics Drives Membrane Morphologies

We study the role of the membrane recycling on the morphology of closed membranes, such as those encountered on organelles within the eukaryotic cell. These constantly exchange membrane material amongst themselves, encapsulated in small transport vesicles, along highly regulated trafficking pathways. The process of fusion and fission is performed by a complex interacting biochemical network of proteins, requiring chemical energy via the hydrolysis of ATP or GTP.

We develop a general theory that allows us to study the dynamical interplay of such active processes with the membrane morphology and the hydrodynamics of the ambient fluid. This is facilitated by an appropriate coarse-graining over the microscopic biochemical reactions, which provides us with large-scale properties of such active membranes. The activity leads to a dynamical renormalization of the membrane parameters, which in turn drives the membrane shape to nonequilibrium steady-states with distinct morphologies that have no analogue in equilibrium physics. For instance, even under conditions of spatially isotropic activity, the membrane may spontaneously acquire a drift. We believe that these processes play an important role to organelles such as Golgi and Endosomes that are driven by the active trafficking dynamics.