Beating Vesicles: Encapsulated Protein Oscillations Cause Dynamic Membrane Deformations

Abstract

The bacterial Min protein system was encapsulated in giant unilamellar vesicles (GUVs). Using confocal fluorescence microscopy, we identified several distinct modes of spatiotemporal patterns inside spherical GUVs. For osmotically deflated GUVs, the vesicle shape actively changed in concert with the Min oscillations. The periodic relocation of Min proteins from the vesicle lumen to the membrane and back is accompanied by drastic changes in the mechanical properties of the lipid bilayer. In particular, two types of oscillating membrane‐shape changes are highlighted: 1) GUVs that repeatedly undergo fission into two connected compartments and fusion of these compartments back into a dumbbell shape and 2) GUVs that show periodic budding and subsequent merging of the buds with the mother vesicle, accompanied by an overall shape change of the vesicle reminiscent of a bouncing ball. These findings demonstrate how reaction–diffusion‐based protein self‐organization can directly yield visible mechanical effects on membrane compartments, even up to autonomous division, without the need for coupling to cytoskeletal elements.

A synthetic morphogenic membrane system that responds with self-organized shape changes to local light cues

“…By equipping SynMMS with an artificial photosynthetic membrane 45 , light energy could be converted into ATP or even GTP chemical potential 46 that could maintain its non-equilibrium state over prolonged periods. Finally, recent progress in reconstituting self-replicating DNA by its encoded proteins in liposomes 47 , bacterial cell division 12 and lipid metabolism 48 suggests 35…”

“…Based on prior work relating local geometric features of the plasma membrane to signaling activity 10 , we have postulated that a closed loop causality between membrane shape, signalling and cytoskeletal dynamics underlies cellular 25 morphological responses 11 . How such cellular functionalities emerge from the dynamics of interacting sub-systems can be experimentally addressed in synthetic proto-cells where the functional molecular modules are encapsulated under non-equilibrium conditions 12 . Previous reconstitutions, although mainly focused on the interplay between the MT-cytoskeleton and motor proteins, have already revealed much about the fundamental mechanisms of self-30 organized cell polarity [13][14][15][16][17][18][19] .…”

Functional Modules of Minimal Cell Division for Synthetic Biology

“…[56,63,66] This results in an assembly of FtsZ at the mid-cell position, where the local time-averaged concentration of the inhibitor MinC is the lowest. [68] Thus, the in vitro reaction and diffusion system of MinD and MinE can be used for the localization of molecules in vesicles or on supported lipid bilayers as well as for the deformation and transformation of GUVs for synthetic biology. The positioning by MinDE in vitro is independent of the membrane anchor of the target molecule, the type of molecule (DNA or protein), the oligomerization state of the target, or the residence time of the target at the membrane.…”

“…Besides the spatiotemporal patterns of the spherical vesicles, something unexpected could be observed by the protein oscillation: Morphology of GUVs that were visibly osmotically deflated underwent extensive shape fluctuations in response to the MinDE oscillations. [68] Thus, the in vitro reaction and diffusion system of MinD and MinE can be used for the localization of molecules in vesicles or on supported lipid bilayers as well as for the deformation and transformation of GUVs for synthetic biology. Moreover, Z-ring positioning is especially important for the design of rod-shaped biomimetic systems.…”

Microfluidic trapping of vesicles reveals membrane-tension dependent FtsZ cytoskeletal re-organisation

“…Examples of more biological meaningful compartments have been reported, such as polymersomes or giant unilamellar vesicles (GUVs). 8,19 We and others have also reconstituted Min protein patterns in more cell-like settings, such as in PDMS microcompartments, [20][21][22] in lipid droplets 23 , on the outside of lipid vesicles, 24 and inside lipid vesicles 25 . However, bacteria are not spherical, and it is clear that cell shape has a great impact on the boundary conditions of these processes.…”