Limits...
Bioinspired membrane-based systems for a physical approach of cell organization and dynamics: usefulness and limitations.

Lagny TJ, Bassereau P - Interface Focus (2015)

Bottom Line: Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research.We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications.Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?

View Article: PubMed Central - PubMed

Affiliation: Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France.

ABSTRACT
Being at the periphery of each cell compartment and enclosing the entire cell while interacting with a large part of cell components, cell membranes participate in most of the cell's vital functions. Biologists have worked for a long time on deciphering how membranes are organized, how they contribute to trafficking, motility, cytokinesis, cell-cell communication, information transport, etc., using top-down approaches and always more advanced techniques. In contrast, physicists have developed bottom-up approaches and minimal model membrane systems of growing complexity in order to build up general models that explain how cell membranes work and how they interact with proteins, e.g. the cytoskeleton. We review the different model membrane systems that are currently available, and how they can help deciphering cell functioning, but also list their limitations. Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research. We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications. Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?

No MeSH data available.


Related in: MedlinePlus

Towards functional cell modules. (a) Encapsulation of either purified components or cell extracts into small containers that are permeable for the required building blocks and energy carriers allows the sustained activity of bioreactors in which high yields of protein can be achieved providing the protein encoding DNA. This requires the functional integrity of both a transcriptional and translational system. (b) Autonomously dividing cell module. Two-dimensional confinement results in the generation of a protein pattern that leads to the definition of a ‘centre’. Recruitment of proteins towards this centre leads to formation of a contractile ring that creates a furrow, which finally leads to fission after recruitment of curvature sensitive proteins. (c) Autonomously crawling cell module. The cell module consists of adhesion molecules that are present on the outside and a dynamic actin network on the inside. After initial adhesion to a substrate, symmetry breaking is caused by geometrical constraints and an adhesion gradient (higher concentration of adhesion molecules or stronger interacting adhesion molecules inside channel). The actin dynamics are now able to generate a force towards the channel, which results in net movement of the cell module until completely having entered the channel.
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RSFS20150038F3: Towards functional cell modules. (a) Encapsulation of either purified components or cell extracts into small containers that are permeable for the required building blocks and energy carriers allows the sustained activity of bioreactors in which high yields of protein can be achieved providing the protein encoding DNA. This requires the functional integrity of both a transcriptional and translational system. (b) Autonomously dividing cell module. Two-dimensional confinement results in the generation of a protein pattern that leads to the definition of a ‘centre’. Recruitment of proteins towards this centre leads to formation of a contractile ring that creates a furrow, which finally leads to fission after recruitment of curvature sensitive proteins. (c) Autonomously crawling cell module. The cell module consists of adhesion molecules that are present on the outside and a dynamic actin network on the inside. After initial adhesion to a substrate, symmetry breaking is caused by geometrical constraints and an adhesion gradient (higher concentration of adhesion molecules or stronger interacting adhesion molecules inside channel). The actin dynamics are now able to generate a force towards the channel, which results in net movement of the cell module until completely having entered the channel.

Mentions: The long-term goal is to build a sort of ‘factory-GUV’ that would (i) be able to produce its own energy (ii) to generate molecules or new proteins from amino acids that could be present on the GUV exterior and supplied to the GUV interior by transporters present into the lipid bilayer (iii) whereas other carriers would take care of the wastes (figure 3a). A system able to express its own ATP-synthases and carriers and to directly incorporate them into the GUV membrane would be even better. Along these directions, transcription and translation machineries must be isolated and encapsulated into GUVs. The first method consisted of using cell extracts where the endogenous genetic material was replaced by bacteriophage RNA polymerase. Next, the protein synthesis using recombinant elements system (PURE system), a minimal synthesis system that uses only a set of purified components [86], has been really instrumental and has allowed the incorporation of membrane proteins in different model membrane systems, including liposomes (see [87] or [88] for recent reviews). In addition, in a first generation, energy supply and nutrient molecules can be located outside the vesicle container and transported through pores or transporters across the bilayer [87] after proper adjustment of the lipid composition [89]. However, with progress in membrane protein reconstitution (§2.1), it might become possible to reconstitute the machinery for ATP production. In addition to the ATP-synthase incorporation, a pH gradient has to be prepared which might be possible if a multi-compartment vesicle is formed. So far, separate compartments have been prepared using the phase transfer of multiple droplets, that can communicate using toxin pores [90], but methods have to be adapted to GUVs.Figure 3.


Bioinspired membrane-based systems for a physical approach of cell organization and dynamics: usefulness and limitations.

Lagny TJ, Bassereau P - Interface Focus (2015)

Towards functional cell modules. (a) Encapsulation of either purified components or cell extracts into small containers that are permeable for the required building blocks and energy carriers allows the sustained activity of bioreactors in which high yields of protein can be achieved providing the protein encoding DNA. This requires the functional integrity of both a transcriptional and translational system. (b) Autonomously dividing cell module. Two-dimensional confinement results in the generation of a protein pattern that leads to the definition of a ‘centre’. Recruitment of proteins towards this centre leads to formation of a contractile ring that creates a furrow, which finally leads to fission after recruitment of curvature sensitive proteins. (c) Autonomously crawling cell module. The cell module consists of adhesion molecules that are present on the outside and a dynamic actin network on the inside. After initial adhesion to a substrate, symmetry breaking is caused by geometrical constraints and an adhesion gradient (higher concentration of adhesion molecules or stronger interacting adhesion molecules inside channel). The actin dynamics are now able to generate a force towards the channel, which results in net movement of the cell module until completely having entered the channel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590427&req=5

RSFS20150038F3: Towards functional cell modules. (a) Encapsulation of either purified components or cell extracts into small containers that are permeable for the required building blocks and energy carriers allows the sustained activity of bioreactors in which high yields of protein can be achieved providing the protein encoding DNA. This requires the functional integrity of both a transcriptional and translational system. (b) Autonomously dividing cell module. Two-dimensional confinement results in the generation of a protein pattern that leads to the definition of a ‘centre’. Recruitment of proteins towards this centre leads to formation of a contractile ring that creates a furrow, which finally leads to fission after recruitment of curvature sensitive proteins. (c) Autonomously crawling cell module. The cell module consists of adhesion molecules that are present on the outside and a dynamic actin network on the inside. After initial adhesion to a substrate, symmetry breaking is caused by geometrical constraints and an adhesion gradient (higher concentration of adhesion molecules or stronger interacting adhesion molecules inside channel). The actin dynamics are now able to generate a force towards the channel, which results in net movement of the cell module until completely having entered the channel.
Mentions: The long-term goal is to build a sort of ‘factory-GUV’ that would (i) be able to produce its own energy (ii) to generate molecules or new proteins from amino acids that could be present on the GUV exterior and supplied to the GUV interior by transporters present into the lipid bilayer (iii) whereas other carriers would take care of the wastes (figure 3a). A system able to express its own ATP-synthases and carriers and to directly incorporate them into the GUV membrane would be even better. Along these directions, transcription and translation machineries must be isolated and encapsulated into GUVs. The first method consisted of using cell extracts where the endogenous genetic material was replaced by bacteriophage RNA polymerase. Next, the protein synthesis using recombinant elements system (PURE system), a minimal synthesis system that uses only a set of purified components [86], has been really instrumental and has allowed the incorporation of membrane proteins in different model membrane systems, including liposomes (see [87] or [88] for recent reviews). In addition, in a first generation, energy supply and nutrient molecules can be located outside the vesicle container and transported through pores or transporters across the bilayer [87] after proper adjustment of the lipid composition [89]. However, with progress in membrane protein reconstitution (§2.1), it might become possible to reconstitute the machinery for ATP production. In addition to the ATP-synthase incorporation, a pH gradient has to be prepared which might be possible if a multi-compartment vesicle is formed. So far, separate compartments have been prepared using the phase transfer of multiple droplets, that can communicate using toxin pores [90], but methods have to be adapted to GUVs.Figure 3.

Bottom Line: Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research.We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications.Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?

View Article: PubMed Central - PubMed

Affiliation: Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France.

ABSTRACT
Being at the periphery of each cell compartment and enclosing the entire cell while interacting with a large part of cell components, cell membranes participate in most of the cell's vital functions. Biologists have worked for a long time on deciphering how membranes are organized, how they contribute to trafficking, motility, cytokinesis, cell-cell communication, information transport, etc., using top-down approaches and always more advanced techniques. In contrast, physicists have developed bottom-up approaches and minimal model membrane systems of growing complexity in order to build up general models that explain how cell membranes work and how they interact with proteins, e.g. the cytoskeleton. We review the different model membrane systems that are currently available, and how they can help deciphering cell functioning, but also list their limitations. Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research. We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications. Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?

No MeSH data available.


Related in: MedlinePlus