Sarina Veit (left) and Thomas Günther-Pomorski are observing individual proteins under a microscope.
Photo Credit: © Günther-Pomorski
Scientific Frontline: Extended "At a Glance" Summary: Single-Protein Microscopy for Lipid Transporters
The Core Concept: A novel, high-throughput microscopy platform enables scientists to isolate and analyze individual lipid transport proteins within microscopic synthetic membrane spheres. This technique allows researchers to track the specific behaviors and speeds of single proteins rather than relying on generalized averages.
Key Distinction/Mechanism: Conventional ensemble methods measure millions of proteins simultaneously, providing only average transport values. This new single-vesicle fluorescence microscopy method overcomes that limitation by analyzing hundreds of 200-nanometer spheres—each containing just one protein molecule—revealing dramatic, hidden variations in their individual transport speeds and activity levels.
Major Frameworks/Components:
- Synthetic Membrane Spheres: Tiny, 200-nanometer vesicles designed to isolate single lipid transport proteins for granular observation.
- VDAC1 Protein: A target protein critical for supplying mitochondria with lipids. It requires assembly into a dimer to function, but its transport efficiency varies wildly based on specific spatial configurations.
- High-Throughput Fluorescence Imaging: The highly sensitive technological method utilized to precisely measure the rate at which an individual protein moves lipids across a membrane.
Branch of Science: Biochemistry, Biophysics, and Molecular Biology.
Future Application: The platform's flexibility allows it to examine a wide range of proteins and environmental factors (like membrane lipid composition or cofactors). This could unlock new drug targets and treatments for mitochondrial dysfunctions, blood diseases, and disrupted cell death mechanisms.
Why It Matters: Lipid transport is fundamental to life, responsible for cell membrane maintenance and crucial signaling pathways. By proving that individual proteins do not behave identically, this research fundamentally advances our granular understanding of vital cellular mechanics.
A new microscopy platform makes hidden differences between individual proteins visible and provides new insights into lipid transport across membranes.
Conventional methods generally analyze many proteins simultaneously. Consequently, the specific traits of individual protein molecules often remain unclear. A research team led by Dr. Sarina Veit and Professor Thomas Günther-Pomorski at Ruhr University Bochum, Germany, in collaboration with researchers from Weill Cornell Medicine in New York and the University of Toronto, Canada, has developed a new microscopy platform that overcomes this limitation. The method allows the simultaneous examination of hundreds of tiny membrane spheres, each with a diameter of approximately 200 nanometers. Each synthetic membrane sphere contains a single lipid transport protein. Using this method, researchers can conduct measurements at the level of individual protein molecules. Additionally, the platform is flexible enough to examine other proteins.
Lipid Transport Is Essential to Life
Every cell in the body is surrounded by a membrane—a thin, flexible shell consisting primarily of lipids. These lipids must be transported across both sides of the membrane, a task performed by specialized lipid transport proteins. “This transport is essential for many vital functions, including the formation and maintenance of cellular membranes, supplying mitochondria with lipids, and transmitting signals during programmed cell death,” Veit explains.
Previously, lipid transporters were primarily examined using ensemble measurements, in which millions of proteins are analyzed simultaneously. However, such methods provide only average values and cannot distinguish between individual proteins; thus, individual characteristics and behaviors remain obscured. The international research team overcame this limitation. By integrating highly sensitive imaging technology into this high-throughput method, the researchers precisely measured, for the first time, how quickly an individual protein transports lipids across the membrane.
Not All Proteins Act in the Same Way
The researchers applied the new method to the protein VDAC1. This protein plays a key role in supplying mitochondria with lipids and is active only when two protein molecules assemble into a dimer. “The tests have shown that the individual VDAC1 proteins do not behave identically at all,” Günther-Pomorski says. “While some dimers transported thousands of lipids per second, others were much slower or entirely inactive.” Past ensemble experiments did not discover this previously unknown variability, which can be explained by differences in how VDAC1 proteins form pairs. Only specific spatial configurations offer a suitable surface for efficient lipid transport, a finding corroborated by computer simulations.
Flexible Method
The new platform is unique because it is not limited to a single protein and offers broad flexibility. Future studies can examine a range of proteins involved in various biological processes. Furthermore, the method enables the selective analysis of how different factors influence transport activity. These factors include various membrane lipid compositions or cofactors, such as specific ions.
“A deeper understanding of the functionality of lipid transporters could, in the long term, open new paths in researching illnesses related to mitochondrial dysfunctions, blood diseases, or disrupted cell death processes,” Veit explains. “Perhaps lipid transporters could even serve as new drug targets.”
Funding: The National Institutes of Health (US), the Canadian Institutes of Health Research, and the German Research Foundation supported the study. Funding was provided to Dr. Sarina Veit (VE 1674/1-1) and Professor Thomas Günther-Pomorski (GU 1133/13-1, INST 213/985-1) of Ruhr University Bochum, among others.
Published in journal: Nature Structural & Molecular Biology
Title: A single-vesicle fluorescence microscopy platform to quantify phospholipid scrambling
Authors: Sarina Veit, Grace I. Dearden, Kartikeya M. Menon, Faria Noor, Indu Menon, Takefumi Morizumi, Oliver P. Ernst, Anant K. Menon, and Thomas Günther Pomorski
Source/Credit: Ruhr-Universität Bochum | Meike Drießen
Edited by: Scientific Frontline
Reference Number: bchm061726_01