Observing the individual fusion events revealed an unprecedented detailed picture of membrane fusion, which was chronicled in one of the cover stories in the December 2006 issue of the journal Proceedings of National Academy of Sciences (PNAS).
"Undoubtedly, understanding the mechanisms of this basic life phenomenon is of great biological interest, and there have been extensive studies at the theoretical and experimental level to this end," stated Taekjip Ha, a professor of physics at Illinois and a Howard Hughes Medical Institute investigator. "Previous studies suggested various physical intermediates for the membrane fusion, but the limitations of the approaches at hand did not allow a solid consensus to be reached."
Compartmentalization in cells is achieved by lipid membranes. Membrane fusion is an elementary biological event which comes in various forms. From cellular trafficking to neuro-transmitter release, merging of two membranes is essential for carrying out vital processes of life. This important task is executed by membrane proteins called SNAREs. Complementary SNARE proteins residing within the incoming and target membranes form a bundle, and bring the two membranes close enough for the merging to occur. The fusion is thought to proceed through highly fleeting intermediates that are very difficult to study when many membrane fusion events are averaged over as has been done in most of previous studies.
Alternatively, the Illinois team, led by Ha, developed an elegant method which used fluorescence resonance energy transfer (FRET) technique to detect SNARE mediated membrane fusion. In FRET, a pair of green and red dyes is used where only the green dye can directly be excited by a laser. The red dye lights up if some of the energy from the green dye hops over to the red dye which becomes increasingly efficient at short distances. Their team prepared two different batches of SNARE-decorated vesicles, one with the green dyes and the other red dyes, and observed them using highly sensitive fluorescence microscopy.
The vesicles with the red dyes were then specifically immobilized on a polymer-passivated glass surface. The polymer coating acted as a cushion and prevented the non-specific binding of vesicles on the surface. As the green labeled vesicles were injected into the flow chamber, the vesicles could fuse upon SNARE-SNARE interaction. The merging of the two membranes result in mixing of the dyes and the level of mixing is reflected as changes in the FRET signal. Using this approach, the researchers could obtain real-time movies of fusion events single vesicles and uncovered various intermediates and pathways during the fusion reaction. The different fates of liposomes subsequent to fusion were also dissected at the level of single-fusion events. The results of the study was highlighted by a commentary in the same issue of the journal PNAS and by a "News and Views" article in the January issue of Nature Structural and Molecular Biology.
The new single-vesicle approach to study membrane fusion, developed by postdoctoral associate Tae-Young Yoon and graduate student Burak Okumus, opens not only a new avenue for the SNARE field, but also provides a native-like environment for the single molecule studies of membrane proteins which would fill a gap in the researchers' toolkit. The work was done in collaboration with Fan Zhang and Professor Yeon-Kyun Shin of Iowa State University and was funded by grants from the National Institute of General Medical Sciences. The research team is currently working on the neuronal SNAREs hoping to shed new light on the membrane fusion events essential for brain functioning.
Richard Kubetz | EurekAlert!
Visualizing gene expression with MRI
23.12.2016 | California Institute of Technology
Illuminating cancer: Researchers invent a pH threshold sensor to improve cancer surgery
21.12.2016 | UT Southwestern Medical Center
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
19.01.2017 | Earth Sciences
19.01.2017 | Life Sciences
19.01.2017 | Physics and Astronomy