Cellular function and malfunction depend crucially on the interactions of proteins and other cellular components. Interactions specifically with lipid membranes are key to the compartmentalization of a wide range of cellular mechanisms into discrete organelles, allowing to maintain homeostasis. A detailed understanding of the mechanisms by which lipid surfaces take part in the control of protein function is therefore of fundamental importance. Understanding these interactions also has important pharmaceutical implications, as ~60% of drug targets are known to be membrane-associated proteins. Despite the implications to life sciences and drug discovery, our current understanding of protein–lipid interactions is limited. This is primarily due to the challenges of existing methods to accurately determine the interactions between proteins and lipid bilayers due to the high level of heterogeneity of the formed complexes.
Recent advances in the development of microfluidic techniques that allow the characterisation of biomolecular complexes together with the availability of sensitive optical detection methods however, open new possibilities for fundamental studies of protein–lipid interactions. The project MicroProtLip focused on overcoming current limitations by establishing a novel, game-changing experimental microfluidic platform to elucidate the dynamic membrane protein interactions in a lipid bilayer context, and in a qualitative and quantitative manner. This project was performed at the University of Cambridge as well as Fluidic Analytics, a company that has pioneered the development of a microfluidic platform that allows the characterization of biomolecular interactions in solution and without surface constraints. The main objective of the MicroProtLip project was the development of transformative assays for microfluidic platforms dedicated for the study of interactions of lipid membranes with protein molecules. Microfluidic technologies, that allow for manipulation of liquids at the microscale, were used for dividing complex samples into fractions. By bringing together single-molecule interrogation with microfluidics, we are aiming to bridge the gap of a missing technology that enables probing interactions and self-assembly of proteins within a lipid bilayer context.
Our novel approach was used to address questions that concern a wide range of aspects of mechanism of protein–lipid interaction such as the mechanism by which α-synuclein – a protein linked genetically and neuropathologically to Parkinson’s disease – binds to lipid surfaces. Interplay between α-synuclein and lipid surfaces was reported to be important for both the physiological function of protein as well as to induce aggregation (a hallmark of the development of Parkinson’s Disease). The focus is on the ability of transient toxic oligomeric forms to bind to lipids and disrupt vesicles. We also utilized this new approach to detect proteins present on the surface of extracellular vesicles – lipid vesicles produced by cells and circulating in body fluids. Proteins displayed on the surface and inside of exosomes provide unique information about the molecular characteristics of the microenvironment and have vast potential in the early detection and monitoring of the progression of cancer. Characterization of the vesicles that are present at low concentrations with sensitive methods will advance the novel approach in diagnostics of early signs of disease. The exemplary problems addressed in the MicroProtLip project have wide implications for society, by adding towards a better understanding of molecular processes in increasingly more prevalent diseases that could in the future lead to the development of new drugs.
