Self-organization keeps schools of fish, flocks of birds and colonies of termites in sync. It's also, according to new research, the way cells regulate the final stage of cell division. Scientists at Rockefeller University have shown that a protein-chemistry-based contour map, which helps individual proteins locate the center of their cell without direction from a "master organizer," is key to ensuring accurate division during mitosis. The finding is reported in the June 19 issue of Nature.
In self-organizing systems, each individual, whether bird, fish, termite or protein, constantly receives and evaluates visual and chemical signals in order to maintain position or determine action, and properties and patterns of the larger whole system emerge from a multiplicity of simple local interactions. Scientists have hypothesized that similar systems exist in cells to carry out numerous functions. The Rockefeller team, led by Professor Tarun Kapoor, head of the Laboratory of Chemistry and Cell Biology, focused on a self-organizing system in mitosis.
As a cell divides, chromosomes in the nucleus duplicate, separate and move to the outer edge of the cell while the cell membrane pinches inward in the middle to form a structure called the cleavage furrow. In order to do this, the cell must know where its middle is.
Kapoor, working with colleagues in his laboratory and at the University of Virginia School of Medicine, tracked the activity of a key regulator of mitosis, a protein called Aurora B. Aurora is a kinase, an enzyme that attaches phosphate chemical groups to proteins in a process called phosphorylation. Other enzymes, called phosphatases, reverse this process by removing phosphates.
To follow Aurora activity, the researchers, in collaboration with Alison North of Rockefeller's Bio-Imaging Resource Center, adapted a powerful microscopy technique called FRET imaging, which measures how close two fluorescent molecules are to each other. Chemical modification of proteins cannot easily be visualized with microscopes, so Kapoor and his colleagues engineered a biosensor to measure the balance between phosphorylation by Aurora and dephosphorylation by phosphatases.
The biosensor was anchored to different sites in the cell -- the equivalent of positioning a microphone at different locations in a room -- then analyzed how the information changes over time. The findings: proteins in the middle of the cell had a higher probability of being phosphorylated by Aurora kinase than those located near the edges.
"Aurora kinase essentially generates a protein chemistry-based contour map, which tells individual molecular players where the middle is," says Kapoor. "And the middle is where there would be the highest probability of being modified by Aurora kinase. It's roughly equivalent, Kapoor says, to a self-organizing school of fish, in which fish in the middle feel something different from the fish on the edges.
"What's really exciting is the discovery of a phosphorylation gradient by tracking in living cells the chemical modifications of proteins," says Kapoor. "We can't actually see aurora kinase activity itself, but we can look at the balance of the phosphorylation of a reporter substrate that depends on this kinase."
"This remarkable study shows how an enzyme, aurora B, governs a key step in cell division: positioning of the cleavage furrow," said Richard Rodewald, who oversees cell division grants at the National Institute of General Medical Sciences, which partially supported the research. "This study also underscores the value of the new generation of fluorescent probes for visualizing in exquisite detail the inner workings of living cells."
Joseph Bonner | newswise
How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH
A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology