Cell-surface mimics
The surface of the cell is very complex, consisting of a variety of biomolecules- lipids, sugars and proteins- that are constantly being reorganized and altered. In order to allow systematic investigations of the roles these individual biomolecules play in virus-membrane interactions, we utilize cell-surface mimics which simplify the molecular architecture of the cell surface. These can be completely artificial, or they can incorporate native membrane extracts. With this approach, we can elucidate specific aspects of the virus-membrane interactions.
The staggering complexity of the cell surface has stimulated the development of artificial cell-surface models capable of reproducing the basic physical and chemical properties of the cell membrane and its components, in cell-free systems.
When producing cell-surface mimics, researchers have often favored bottom-up approaches which rely on incorporating, one or a few selected ligands interacting with the virus, into a self-assembled structure reproducing the native environment of the cell membrane. Such a reductionist approach allows us to systematically investigate the influence of both individual and combinations of viral receptors on virus-membrane interactions while controlling parameters, such as ligand density or mobility. Many human pathogenic viruses bind to ubiquitous carbohydrates called glycosaminoglycans (GAGs) found on the cell surface. In the context of studying GAG-mediated biomolecular interactions, our lab takes advantage of a platform based on the end-on immobilization of GAG-chains in a configuration mimicking the attachment of the glycans to the proteoglycan core (Figure A). [1,2] In order to investigate virus-(glyco)lipid interactions in a more native environment that recreates fluidity of the cell membrane , we utilize various (glyco)lipid-containing lipid assemblies. These can take the form of supported lipid bilayers (SLBs), where a lipid membrane is deposited onto a solid support or unilamellar vesicles of various sizes (Figure B), depending on the assay configuration and read-out to be used. [3, 4]
Some research projects rather require us to study virus-membrane interactions top-down i.e. with a cell surface model incorporating the complete repertoire of plasma membrane components. In our lab, we therefore work with native supported lipid bilayers (nSLBs) which are SLBs produced directly from the cell membrane of interest (Figure C). [5, 6] The cell-free nSLB platform provides a temporal snapshot of the cell surface displaying its full compositional complexity, but decoupled from the physiological feed-back loops present in a living cell.
Our lab uses this broad spectrum of cell-membrane mimics complemented with in vitro cell experiments to provide detailed mechanistic insights into how viruses attach, detach, and diffuse at cellular surfaces.
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