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Developmental Biology - Cell Membrane Receptors

Changing How We Study Disease?

A new way of looking at cell membranes could change the way we study and fight disease...

Researchers have developed a new technique to analyse cell membrane proteins in situ which could revolutionise the way in which we study diseases, such as cancer, metabolic and heart diseases. The discovery was made as part of an international research collaboration, led by Oxford University, along with the Imperial College London. The technique could dramatically affect our understanding of both how cell membrane complexes work, and in the process, our approach to healthcare research.

Membranes protect all of our cells and the organelles inside them, including the mitochondria - the power sources of the cell. Cell membranes are studded with biological machinery made out of proteins that enable molecular cargo to pass in and out. Research, published in Science, promotes the development of the powerful tool now used to analyse the make-up of matter (mass spectrometry) to take biology to a new level. It wouls enable new discoveries not seen possible before.

Studying cell membrane-embedded machines in their native state is crucial to understanding mechanisms of disease — while also providing new goals for treatments. However, current methods for studying these mechanisms involves removing them from the cell membrane, which can alter their structure and function.

"For decades, scientists have had to extract these proteins from their membranes for their studies. But imagine what you might discover if you could get proteins straight from the membrane into a mass spectrometer? I wasn't sure this would ever work. I thought the membrane environment would be just too complicated and we wouldn't be able to understand the results. I am delighted that it has because it has given us a whole new view of an important class of drug targets," says lead researcher Professor Dame Carol Robinson, Professor of Physical Chemistry at Oxford University in the Department of Chemistry.
The technique involves vibrating the sample at ultrasonic frequencies so that the cell begins to fall apart. Electrical currents then applied an electric field to eject the protein machines out of the membrane and directly into a mass spectrometer - an instrument that can detect a molecule's chemical 'signature', based on its mass.

Not only did the membrane protein machines survive the ejection, their analysis revealed:
• How they communicate with each other
• How they are guided to their final location
• How transport of their molecular cargo into the cell occurs.

Professor Steve Matthews, Department of Life Sciences, Imperial adds: "With the development of this method, the application of mass spectrometry in biology will be taken to a new level, using it to make discoveries that would not have been possible before."
"A longstanding question on the structure of one membrane machine from mitochondria has now been solved using this technique. Mitochondria are particularly interesting because there are several diseases that target them specifically, that we may now be able to design new therapies for."

Sarah L. Rouse PhD, Department of Life Sciences, Imperial College, London, England.

"The results are particularly exciting for mitochondrial membranes — we managed to catch a translocator in action — passing metabolites. Because mitochondrial therapeutics target a wide range of debilitating diseases, we now have a new way of assessing their effects."

Carol Robinson PhD, Professor of Chemistry, University of Oxford and Dame Commander of the Order of the British Empire.

Insights into the architecture and stoichiometry [the relationship between relative quantities of substances in a reaction or compound; typically a ratio of whole numbers] of membrane complexes have grown with advances in cryo–electron microscopy and native mass spectroscopy. However, most of these studies are not in the context of native membrane. Chorev et al. released intact membrane complexes directly from native lipid membrane vesicles into a mass spectrometer. They analyzed components of the Escherichia coli inner and outer membranes and the bovine mitochondrial inner membrane. For several identified complexes, they found a stoichiometry that differs from published results and, in some cases, confirmed interactions that could not be characterized structurally. Science, this issue p. 829

Nanomedicines can be taken up by cells via nonspecific and dynamin-dependent (energy-dependent) clathrin and caveolae-mediated endocytosis. While significant effort has focused on targeting pathway-specific transporters, the role of nanobiophysics in the cell lipid bilayer nanoparticle uptake pathway remains largely unexplored. In this study, it is demonstrated that stiffness of lipid bilayer is a key determinant of uptake of liposomes by mammalian cells. Dynamin-mediated endocytosis (DME) of liposomes is found to correlate with its phase behavior, with transition toward solid phase promoting DME, and transition toward fluidic phase resulting in dynamin-independent endocytosis. Since liposomes can transfer lipids to cell membrane, it is sought to engineer the biophysical properties of the membrane of breast epithelial tumor cells (MD-MBA-231) by treatment with phosphatidylcholine liposomes, and elucidate its effect on the uptake of polymeric nanoparticles. Analysis of the giant plasma membrane vesicles derived from treated cells using flicker spectroscopy reveals that liposome treatment alters membrane stiffness and DME of nanoparticles. Since liposomes have a history of use in drug delivery, localized priming of tumors with liposomes may present a hitherto unexploited means of targeting tumors based on biophysical interactions.

Dror S. Chorev, Lindsay A. Baker, Di Wu, Victoria Beilsten-Edmands, Sarah L. Rouse, Tzviya Zeev-Ben-Mordehai, Chimari Jiko, Firdaus Samsudin, Christoph Gerle, Syma Khalid, Alastair G. Stewart, Stephen J. Matthews, Kay Grünewald and Carol V. Robinson.

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Jan 18, 2019   Fetal Timeline   Maternal Timeline   News   News Archive

Vibrating at ultrasonic frequencies, a cell begins to fall apart. Electrical current is applied that
separates the protein 'machines' being ejected, thus detecting a molecule's chemical mass.

Phospholid by Wikipedia