3 scientists share 2013 Nobel Prize in Medicine

The 2013 Nobel Prize in Physiology or Medicine awarded to scientist Schekman, Rothman and Suedhof The Nobel Assembly at Karolinska Institute awarded The 2013 Nobel Prize in Physiology or Medicine jointly to 1) James E. Rothman, Randy [USA], 2)W. Schekman [USA], 3)Thomas C. Südhof [Germany], Award Money - $1.2 million, For their discoveries of machinery regulating vesicle traffic, a major transport system in our cells The 2013 Nobel Prize honors three scientists who have solved the mystery of how the cell organizes its transport system. Each cell is a factory that produces and exports molecules. For instance, insulin is manufactured and released into the blood and chemical signals called neurotransmitters are sent from one nerve cell to another. These molecules are transported around the cell in small packages called vesicles. The three Nobel Laureates have discovered the molecular principles that govern how this cargo is delivered to the right place at the right time in the cell. Randy Schekman discovered a set of genes that were required for vesicle traffic. James Rothman unravelled protein machinery that allows vesicles to fuse with their targets to permit transfer of cargo. Thomas Südhof revealed how signals instruct vesicles to release their cargo with precision. Through their discoveries, Rothman, Schekman and Südhof have revealed the exquisitely precise control system for the transport and delivery of cellular cargo. Disturbances in this system have deleterious effects and contribute to conditions such as neurological diseases, diabetes, and immunological disorders. How cargo is transported in the cell In a large and busy port, systems are required to ensure that the correct cargo is shipped to the correct destination at the right time. The cell, with its different compartments called organelles, faces a similar problem: cells produce molecules such as hormones, neurotransmitters, cytokines and enzymes that have to be delivered to other places inside the cell, or exported out of the cell, at exactly the right moment. Timing and location are everything. Miniature bubble-like vesicles, surrounded by membranes, shuttle the cargo between organelles or fuse with the outer membrane of the cell and release their cargo to the outside. This is of major importance, as it triggers nerve activation in the case of transmitter substances, or controls metabolism in the case of hormones. How do these vesicles know where and when to deliver their cargo? Traffic congestion reveals genetic controllers Randy Schekman was fascinated by how the cell organizes its transport system and in the 1970s decided to study its genetic basis by using yeast as a model system. In a genetic screen, he identified yeast cells with defective transport machinery, giving rise to a situation resembling a poorly planned public transport system. Vesicles piled up in certain parts of the cell. He found that the cause of this congestion was genetic and went on to identify the mutated genes. Schekman identified three classes of genes that control different facets of the cell´s transport system, thereby providing new insights into the tightly regulated machinery that mediates vesicle transport in the cell. Docking with precision James Rothman was also intrigued by the nature of the cell´s transport system. When studying vesicle transport in mammalian cells in the 1980s and 1990s, Rothman discovered that a protein complex enables vesicles to dock and fuse with their target membranes. In the fusion process, proteins on the vesicles and target membranes bind to each other like the two sides of a zipper. The fact that there are many such proteins and that they bind only in specific combinations ensures that cargo is delivered to a precise location. The same principle operates inside the cell and when a vesicle binds to the cell´s outer membrane to release its contents. It turned out that some of the genes Schekman had discovered in yeast coded for proteins corresponding to those Rothman identified in mammals, revealing an ancient evolutionary origin of the transport system. Collectively, they mapped critical components of the cell´s transport machinery. Timing is everything Thomas Südhof was interested in how nerve cells communicate with one another in the brain. The signalling molecules, neurotransmitters, are released from vesicles that fuse with the outer membrane of nerve cells by using the machinery discovered by Rothman and Schekman. But these vesicles are only allowed to release their contents when the nerve cell signals to its neighbors. How is this release controlled in such a precise manner? Calcium ions were known to be involved in this process and in the 1990s, Südhof searched for calcium sensitive proteins in nerve cells. He identified molecular machinery that responds to an influx of calcium ions and directs neighbour proteins rapidly to bind vesicles to the outer membrane of the nerve cell. The zipper opens up and signal substances are released. Südhof´s discovery explained how temporal precision is achieved and how vesicles´ contents can be released on command. Vesicle transport gives insight into disease processes The three Nobel Laureates have discovered a fundamental process in cell physiology. These discoveries have had a major impact on our understanding of how cargo is delivered with timing and precision within and outside the cell. Vesicle transport and fusion operate, with the same general principles, in organisms as different as yeast and man. The system is critical for a variety of physiological processes in which vesicle fusion must be controlled, ranging from signalling in the brain to release of hormones and immune cytokines. Defective vesicle transport occurs in a variety of diseases including a number of neurological and immunological disorders, as well as in diabetes. Without this wonderfully precise organization, the cell would lapse into chaos. James E. Rothman was born 1950 in Haverhill, Massachusetts, USA. He received his PhD from Harvard Medical School in 1976, was a postdoctoral fellow at Massachusetts Institute of Technology, and moved in 1978 to Stanford University in California, where he started his research on the vesicles of the cell. Rothman has also worked at Princeton University, Memorial Sloan-Kettering Cancer Institute and Columbia University. In 2008, he joined the faculty of Yale University in New Haven, Connecticut, USA, where he is currently Professor and Chairman in the Department of Cell Biology. Randy W. Schekman was born 1948 in St Paul, Minnesota, USA, studied at the University of California in Los Angeles and at Stanford University, where he obtained his PhD in 1974 under the supervision of Arthur Kornberg (Nobel Prize 1959) and in the same department that Rothman joined a few years later. In 1976, Schekman joined the faculty of the University of California at Berkeley, where he is currently Professor in the Department of Molecular and Cell biology. Schekman is also an investigator of Howard Hughes Medical Institute. Thomas C. Südhof was born in 1955 in Göttingen, Germany. He studied at the Georg-August-Universität in Göttingen, where he received an MD in 1982 and a Doctorate in neurochemistry the same year. In 1983, he moved to the University of Texas Southwestern Medical Center in Dallas, Texas, USA, as a postdoctoral fellow with Michael Brown and Joseph Goldstein (who shared the 1985 Nobel Prize in Physiology or Medicine). Südhof became an investigator of Howard Hughes Medical Institute in 1991 and was appointed Professor of Molecular and Cellular Physiology at Stanford University in 2008.  Source: ArticleImage: Screen Shot On Video
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Gene of the week: internet addiction

Everybody is talking about internet addiction – many people spend hours online and immediately start feeling bad if they are unable to do so. Medically, this phenomenon has not been as clearly described as nicotine or alcohol dependency. But a German study in the Journal of Addiction Medicine suggests that there are molecular-genetic connections in internet addiction, too. "It was shown that Internet addiction is not a figment of our imagination," says the lead author, Dr. Christian Montag of the University of Bonn. "Researchers and therapists are increasingly closing in on it." He found that some people’s thoughts revolve around the internet during the day and that they feel their wellbeing is severely impacted if they have to go without it. The problem users seem to have a genetic variation that also plays a major role in nicotine addiction. "It seems that this connection is not only essential for nicotine addiction, but also for internet addiction," reports the Bonn psychologist. “The current data already shows that there are clear indications for genetic causes of Internet addiction." The actual mutation is on the CHRNA4 gene that changes the genetic make¬up for the Alpha 4 subunit on the nicotinic acetylcholine receptor. "Within the group of subjects exhibiting problematic Internet behavior this variant occurs more frequently – in particular, in women," says Dr. Montag. ~ Universität Bonn press release, Aug 29 Source BioEdgeImage
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Biophysicists unravel secrets of genetic switch

"I hope this kind of experiment will lead to better understanding of how our own DNA is compacted into chromosomes, and how it unravels locally to become expressed," says biophysicist Laura Finzi.
By Carol Clark: When an invading bacterium or virus starts rummaging through the contents of a cell nucleus, using proteins like tiny hands to rearrange the host’s DNA strands, it can alter the host’s biological course. The invading proteins use specific binding, firmly grabbing onto particular sequences of DNA, to bend, kink and twist the DNA strands. The invaders also use non-specific binding to grasp any part of a DNA strand, but these seemingly random bonds are weak. Emory University biophysicists have experimentally demonstrated, for the fist time, how the nonspecific binding of a protein known as the lambda repressor, or C1 protein, bends DNA and helps it close a loop that switches off virulence. The researchers also captured the first measurements of that compaction. Their results, published in Physical Review E, support the idea that nonspecific binding is not so random after all, and plays a critical role in whether a pathogen remains dormant or turns virulent. “Our findings are the first direct and quantitative determination of non-specific binding and compaction of DNA,” says Laura Finzi, an Emory professor of biophysics whose lab led the study. “The data are relevant for the understanding of DNA physiology, and
Lysis plaques of lambda phage on E. coli bacteria.
the dynamic characteristics of an on-off switch for the expression of genes.”C1 is the repressor protein of the lambda bacteriophage, a virus that infects the bacterial species E. coli, and a common laboratory model for the study of gene transcription.The virus infects E. coli by injecting its DNA into the host cell. The viral DNA is then incorporated in the bacterium’s chromosome. Shortly afterwards, binding of the C1 protein to specific sequences on the viral DNA induces the formation of a loop. As long as the loop is closed, the virus remains dormant. If the loop opens, however, the machinery of the bacteria gets hi-jacked: The virus switches off the bacteria’s genes and switches on its own, turning virulent.“The loop basically acts as a molecular switch, and is very stable during quiescence, yet it is highly sensitive to the external environment,” Finzi says. “If the bacteria is starved or poisoned, for instance, the viral DNA receives a signal that it’s time to get off the boat and spread to a new host, and the loop is opened. We wanted to understand how this C1-mediated, loop-based mechanism can be so stable during quiescence,Transient-loop formation, left, occurs due to non-specific binding of proteins (small orange disks) to DNA (black line). DNA is attached at one end to the glass surface of a microscope flow-chamber and at the other end to a magnetic bead (large gray disk) that reacts to the pulling force of a pair of magnets. The weak, non-specific DNA-protein interactions are disrupted as the force increases. (Graphic by Monica Fernandez.) 
and yet so responsive to switching to virulence when it receives the signal to do so.” Finzi runs one of a handful of physics labs using single-molecule techniques to study the mechanics of gene expression. In 2009, her lab proved the formation of the C1 loop. “We then analyzed the kinetics of loop formation and gained evidence that non-specific binding played a role,” Finzi says. “We wanted to build on that work by precisely characterizing that role.” Emory undergraduate student Chandler Fountain led the experimental part of the study. He used magnetic tweezers, which can pull on DNA molecules labeled with miniscule magnetic beads, to stretch DNA in a microscope flow chamber. Gradually, the magnets are moved closer to the DNA, pulling it further, so the length of the DNA extension can be plotted against the applied force. “You get a curve,” Finzi explains. “It’s not linear, because DNA is a spring. Then you put the same DNA in the presence of C1 protein and see how the curve changes. Now, you need more force to get toSpecifically-bound proteins are shown as orange ovals on a thicker part of the DNA sequence and non-specifically bound proteins are portrayed as gray ovals on regular DNA. Non-specific, transient loops facilitate the coming together of the specifically-bound proteins that mediate formation of the “switch loop”. Once this loop is formed, non-specifically bound protein further stabilize it by increasing the length of the closure in a zipper-like effect. (Graphic by Monica Fernandez.)
the same extension because the protein holds onto the DNA and bends it.” An analysis of the data suggests that, while the specific binding of the C1 protein forms the loop, the non-specific binding acts like a kind of zipper, facilitating the closure of the loop, and keeping it stable until the signal comes to open it. “The zipper-like effect of the weaker binding sites also allows the genetic switch to be more responsive to the environment, providing small openings that allow it to breathe, in a sense,” Finzi explains. “So the loop is never permanently closed.” The information about how the C1 genetic switch works may provide insights into the workings of other genetic switches. “Single-molecule techniques have opened a new era in the mechanics of biological processes,” Finzi says. “I hope this kind of experiment will lead to better understanding of how our own DNA is compacted into chromosomes, and how it unravels locally to become expressed.” Other authors on the paper include Sachin Goyal, formerly a post-doc in the Finzi lab; Emory cell biologist David Dunlap; and Emory theoretical physicistFereydoon Family. The research was funded by the National Institutes of Health. Source: eScienceCommons
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