Model Membrane Platforms for Biomedicine: Case Study on Antiviral Drug Development

Abstract

As one of the most important interfaces in cellular systems, biological membranes have essential functions in many activities such as cellular protection and signaling. Beyond their direct functions, they also serve as scaffolds to support the association of proteins involved in structural support, adhesion, and transport. Unfortunately, biological processes sometimes malfunction and require therapeutic intervention. For those processes which occur within or upon membranes, it is oftentimes difficult to study the mechanism in a biologically relevant, membranous environment. Therefore, the identification of direct therapeutic targets is challenging. In order to overcome this barrier, engineering strategies offer a new approach to interrogate biological activities at membrane interfaces by analyzing them through the principles of the interfacial sciences. Since membranes are complex biological interfaces, the development of simplified model systems which mimic important properties of membranes can enable fundamental characterization of interaction parameters for such processes. We have selected the hepatitis C virus (HCV) as a model viral pathogen to demonstrate how model membrane platforms can aid antiviral drug discovery and development. Responsible for generating the genomic diversity that makes treating HCV infection so difficult, viral replication represents an ideal step in the virus life cycle for therapeutic intervention. To target HCV genome replication, the interaction of viral proteins with model membrane platforms has served as a useful strategy for target identification and characterization. In this review article, we demonstrate how engineering approaches have led to the discovery of a new functional activity encoded within the HCV nonstructural 5A protein. Specifically, its N-terminal amphipathic, α-helix (AH) can rupture lipid vesicles in a size-dependent manner. While this activity has a number of exciting biotechnology and biomedical applications, arguably the most promising one is in antiviral medicine. Based on the similarities between lipid vesicles and the lipid envelopes of virus particles, experimental findings from model membrane platforms led to the prediction that a range of medically important viruses might be susceptible to rupturing treatment with synthetic AH peptide. This hypothesis was tested and validated by molecular virology studies. Broad-spectrum antiviral activity of the AH peptide has been identified against HCV, HIV, herpes simplex virus, and dengue virus, and many more deadly pathogens. As a result, the AH peptide is the first in class of broad-spectrum, lipid envelope-rupturing antiviral agents, and has entered the drug pipeline. In summary, engineering strategies break down complex biological systems into simplified biomimetic models that recapitulate the most important parameters. This approach is particularly advantageous for membrane-associated biological processes because model membrane platforms provide more direct characterization of target interactions than is possible with other methods. Consequently, model membrane platforms hold great promise for solving important biomedical problems and speeding up the translation of biological knowledge into clinical applications.

Total internal reflection fluorescence microscopy for determination of size of individual immobilized vesicles: Theory and experiment

“…Expression (12) is similar to (4) and (8), while (13) is similar to (5) and different compared to (9). In particular, the intensity predicted by (13) is much larger than that predicted by (9).…”

“…In particular, the intensity predicted by (13) is much larger than that predicted by (9). Thus, the use of different light polarizations may help to clarify the dye orientation with respect to the vesicle leaflets provided d ( r. If dyes are oriented randomly along the vesicle surface and light is s-or p-polarized, one should just replace sin 2 h sin 2 / by 1 À sin 2 h sin 2 / in Eq.…”

“…8 Such systems can be fabricated via adsorption of vesicles without or with subsequent spontaneous or peptide-induced rupture 8,9 or via the "solventassisted" procedure. 10 The corresponding mass uptake can be determined optically by ellipsometry, waveguide lightmode spectroscopy and surface plasmon resonance, [11][12][13] or by quartz crystal microbalance.…”

Comparison of Extruded and Sonicated Vesicles for Planar Bilayer Self-Assembly

“…Solid-supported planar lipid bilayers formed by the fusion of vesicles with hydrophilic substrates including silicon oxide [15,16] and mica [17,18] are important cell membrane mimics for biosensing and antifouling coatings, and take advantage of robust self-assembly depending on experimental conditions including vesicle size [19], lipid composition [20], ionic strength [21] and solution pH [22,23,24]. With emerging commercial opportunities for these platforms in pharmaceutical drug discovery and development [25], quality control of these platforms needs to be extended to include industry-relevant parameters such as stability of stored vesicles and processing method employed. Although there have been inconsistent findings in the literature that are possibly attributable to the vesicle preparation method [26,27] ( i.e.…”

Kinetics of Single-Enzyme Reactions on Vesicles: Role of Substrate Aggregation

“…to peptides (antimicrobial and antiviral peptides are e.g. known to aggregate and form pores in membranes [33][34][35] ).…”