Autonomous Motion of Artificial Cells Now Made Possible; Scientists Developed Mechanism for Liposome Motility

With the advancement of science, experts can now perform procedures considered impossible in the past. In medicine, scientists cannot only cure diseases but also mimic biological processes, even to the extent of creating artificial cells.

Artificial cells do not only have cell-like structures, but they also have the key functions of living biological cells, like reproduction and metabolism. They can be biological cell imitators or engineered materials with various purposes. However, constructing even the simplest unicellular organisms can be very complicated for scientists. For instance, one of the characteristics of artificial cells with life-like features is autonomous movement using a minimal set of components. Unfortunately, this ability is very difficult to be reproduced in the test tube.

Setting the Cells in Motion

A group of scientists responded to this challenge by developing a mechanochemical feedback loop that enables the persistent movement of cell-sized liposomes. Physicist Erwin Frey led the study from Ludwig-Maximilians-Universitaet Muenchen (LMU) and Petra Schwille from the Max Planck Institute of Biochemistry.

In this study, vesicles are enclosed by a lipid membrane called liposomes, constantly moving on a supporting membrane. This motion is made possible by the interaction of the vesicle membrane and specific protein patterns. A mechanochemical feedback loop between the protein systems of Escherichia coli generates this pattern.

Experiments in the laboratory reveal that the membrane-binding Min proteins in the artificial cells self-organize asymmetrically around the liposomes, resulting in shape deformation and generating a mechanical force that leads to cellular movement. In the process, the protein distribution responds by binding to the supporting membrane and vesicles.

According to Frey's team, the mechanochemical feedback loop between the Min proteins and liposome is enough to generate continuous movement. In higher cells, the complex motor proteins perform the task of directly transporting large membrane vesicles. Scientists were surprised to discover that small bacterial proteins can also carry this out.

Using theoretical analyses, the researchers identified two possible mechanisms responsible for cellular motion. The first possible mechanism has something to do with the interaction of proteins on the supporting membrane and the vesicle surface, acting like a zipper to form molecular compounds. The second possible mechanism proposes that membrane-bound proteins disfigure the vesicle membrane and change its curvature.

As of now, the role of protein molecules at the membrane surface is still unclear, and the researchers are also unsure about the benefit that can be gained by the bacteria from such a function. Despite this, the researchers hope their discovery can serve as a starting point in designing artificial cells with motility features.

How Do Cells Move?

Cell movement refers to the cellular locomotion and the mechanism behind this process. This crucial process has a very significant role in the development and continuity of multicellular organisms.

As a complex event, cell motility is primarily triggered by the actin network below the cell membrane and is divided into three general parts. The first component is the projection of the cell's leading edge, followed by the leading edge and fastening at the cell body. Lastly, the contraction of the cytoskeleton enables the cell to pull itself forward.

Understanding cell movement is very important in studying embryo development and immune defense. The nature of tissue repair and regeneration is also explained by cell movement. Most importantly, it also enables experts to reduce cancer progression and prevent the disease from spreading throughout the body.