A mapmaker and a mathematician may seem like an unlikely duo, but together they worked out a way to measure longitude -- and kept millions of sailors from getting lost at sea. Now, another unlikely duo, a virologist and a biophysicist at Rockefeller University, is making history of their own.
By using a specialized microscope that only illuminates the cell’s surface, they have become the first to see, in real time and in plain view, hundreds of thousands of molecules coming together in a living cell to form a single particle of the virus that has, in less than 25 years, claimed more than 25 million lives: HIV.
This work, published in the May 25 advanced online issue of Nature, may not only prove useful in developing treatments for the millions around the globe still living with the lethal virus but the technique created to image its assembly may also change the way scientists think about and approach their own research.
“The use of this technique is almost unlimited,” says Nolwenn Jouvenet, a postdoc who spearheaded this project under the direction of HIV expert Paul Bieniasz and cellular biophysicist Sandy Simon, who has been developing the imaging technique since 1992. “Now that we can actually see a virus being born, it gives us the opportunity to answer previously unanswered questions, not only in virology but in biology in general.”
Unlike a classical microscope, which shines light through a whole cell, the technique called total internal reflection microscopy only illuminates the cell’s surface where HIV assembles. “The result is that you can see, in exquisite detail, only events at the cell surface. You never even illuminate anything inside of the cell so you can focus on what you are interested in seeing the moment it is happening,” says Simon, professor and head of the Laboratory of Cellular Biophysics.
When a beam of light passes through a piece of glass to a cell’s surface, the energy from the light propagates upward, illuminating the entire cell. But when that beam is brought to a steeper angle, the light’s energy reflects off the cell’s surface, illuminating only the events going on at its most outer membrane. By zeroing in at the cell’s surface, the team became the first to document the time it takes for each HIV particle, or virion, to assemble: five to six minutes. “At first, we had no idea whether it would take milliseconds or hours,” says Jouvenet. “We just didn’t know.”
“This is the first time anyone has seen a virus particle being born,” says Bieniasz, who is an associate professor and head of the Laboratory of Retrovirology at Rockefeller and a scientist at the Aaron Diamond AIDS Research Center. “Not just HIV,” he clarifies, “any virus.”
To prove that what they were watching was virus particles assembling at the surface (rather than an already assembled virion coming into their field of view from inside the cell), the group tagged a major viral protein, called the Gag protein, with molecules that fluoresce, but whose color would change as they packed closer together. Although many different components gather to form a single virion, the Gag protein is the only one necessary for assembly. It attaches to the inner face of the cell’s outer membrane and when enough Gag molecules flood an area, they coalesce in a way that spontaneously forms a sphere.
Simon, Bieniasz and Jouvenet found that the Gag molecules are recruited from the inside of the cell and travel to the cell’s surface. When enough Gag molecules get close and start bumping into each other, the cell’s outer membrane starts to bulge outward into a budding virion and then pinches off to form an individual, infectious particle. At this point, the researchers showed that the virion is a lone entity, no longer exchanging resources with the cell. By using tricks from optics and physiology, they were able to watch the steps of viral assembly, budding, and even scission off the cell surface. With such a view they can start to describe the entire lifeline in the birth of the virus.
“I think that you can begin to understand events on a different level if you actually watch them happen instead of inferring that they might occur using other techniques,” says Bieniasz. “This technique and this collaboration made that possible.”
This research was supported in part by the National Institutes of Health, the National Science Foundation and amFAR, the Foundation for AIDS Research.
Thania Benios | newswise
What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society
Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
23.08.2017 | Life Sciences
23.08.2017 | Life Sciences
23.08.2017 | Physics and Astronomy