Scientists unlock key to cancer cell death mystery

A group led by the University of Leicester has shown that particular cancer cells are especially sensitive to a protein called p21. This protein usually forces normal and cancer cells to stop dividing but it was recently shown that in some cases it can also kill cancer cells.

However, scientists have been unclear about how this happens.

Researcher Salvador Macip, from the University of Leicester Department of Biochemistry, said: "If we could harness this 'killing power' that p21 has, we could think of designing new therapies aimed at increasing its levels in tumours. This is what motivated us to look into it".

Now the team from the universities of Leicester and Cardiff in the UK, University of South Carolina, USA and Karolinska Institutet, Sweden has discovered that cells from sarcomas tend to die in response to p21 and that this is determined by the sensitivity of their mitochondria to oxidants.

They have published their findings in The Journal of Biological Chemistry. The research was funded by the MRC, the NIH, CONACYT and the Swedish Cancer Society

Dr Macip added: "Our research also showed that p21 can kill cells even in the absence of p53, a protein that is in the main responsible for cell death but is inactivated in most cancers.

"This shows that certain types of cancer, sarcomas for instance, but maybe also others, should respond well to drugs that increase the levels of p21, even if they don't have an active p53. The side effects of these therapies should be minimal, since our experiments show that normal cells would arrest but not die in response to p21.

"There are already drugs available that selectively increase p21. Our results provide a rationale for testing them in certain types of cancers, which could be identified using the experiments we describe."

More information: Reactive oxygen species and mitochondrial sensitivity to oxidative stress determine induction of cancer cell death by p21. Masgras I, Carrera S, de Verdier PJ, Brennan P, Majid A, Makhtar W, Tulchinksy E, Jones GD, Roninson IB, Macip S. J Biol Chem. 2012 Feb 6. [Epub ahead of print]

The Journal of Biological Chemistry, Vol. 287, Issue 13, 9845-9854, MARCH 23, 2012

Provided by University of Leicester (news : web)

A 24-karat gold key to unlock the immune system

Using nanoparticles made of pure gold, Dr. Dan Peer, head of Tel Aviv University's Laboratory of Nanomedicine at the Department of Cell Research and Immunology and the Center for Nanoscience and Nanotechnology, with a team including Drs. Meir Goldsmith and Dalit Landesman-Milo and in collaboration with Prof. Vincent Rotello and Dr. Daniel Moyano from the University of Massachusetts at Amherst, has developed a new method of introducing chemical residues into the immune system, allowing them to note the properties that incur the wrath of immune cells. Because the gold flecks are too small to be detected by the immune system, the immune system only responds when they are coated with different chemical residues.

This breakthrough could lead to an increased understanding of the properties of viruses and bacteria, better drug delivery systems, and more effective medications and vaccinations. Their study was published in the Journal of the American Chemical Society.

A tool for exploration

To begin probing the immune system, researchers used particles of gold, approximately two nanometers in diameter, and covered them with various chemical residues. Only when water-resistant residues were introduced did the immune system respond to their presence. That established a demonstrable link between hydrophobicity — the degree to which a molecule repels water — and the reaction of the immune system.

This idea has a basis in the normal functioning of the immune system, Dr. Peer explains. During cell death, the hydrophobic areas of the cell membrane become exposed. The immune system then realizes that damage has occurred and begins to alert neighboring cells.

The researchers discovered that the same principle held true for the chemicals added to the gold particles' surface. The more "water-hating" the particle is, the more actively the immune system will mobilize against it, he says.

Dr. Peer observes that this is only the first step in a long line of experiments. "We are using these gold particles to tackle the question of how the immune system recognizes different particles, which might include features such as geometry, charge, curvature, and so much more. Now that we know the tool works, we can build on it," he says.

Testing the "Danger Model"

Until now, scientists have developed theories about how the immune system functions, but have lacked the machinery to test these ideas. One such theory is the "Danger Model" by Prof. Polly Matzinger, which hypothesizes that cellular damage interacts with immune cells at the membrane level. Once they identify the foreign molecule as a "danger," the immune cells send signals throughout the immune system. Their initial experiment with hydrophobicity was designed to generate a toolbox for probing this theory, says Dr. Peer, whose investigations included both in vitro and in vivo experiments using mouse immune cells.

In the future, researchers will study various bacterial, viral, or damaged cells and to make the gold nanoparticles even more similar, thereby discovering which elements of dangerous particles are calling the body's immune system to arms. "We now have the capability of using nanomaterials to probe the immune system in a very accurate manner," says Dr. Peer, a breakthrough that could revolutionize the way we understand the immune system.

Provided by Tel Aviv University (news : web)

Chemists unlock potential target for drug development

A team led by Dana Spence of MSU's Department of Chemistry has revealed a way to isolate and test the receptor known as P2X1. By creating a new, simple method to study it after blood is drawn, the team has unlocked a potential new drug target for many diseases that impact red blood cells, such as diabetes, hypertension and cystic fibrosis.

Researchers can evaluate the receptor not only in developing new drugs but also re-testing existing medications that could work now by attaching to the receptor.

"Scientists are always looking for new 'druggable' receptors in the human body," Spence said. "This receptor, P2X1, has long been viewed as not important in platelets; our studies show that is not necessarily true. The receptor is very active; you just need to be careful in working with it."

The research is published in the current issue of Analytical Methods, a journal from the Royal Society of Chemistry in London.

The main job of platelets is to help prevent bleeding via clotting, Spence said. They work by getting sticky in the bloodstream, but the problem with some diseases such as diabetes or sickle-cell anemia is that the platelets get sticky even when they shouldn't, preventing proper blood flow and blocking vessels.

Platelets are activated when their receptors are "turned on"; currently, researchers have always focused on the P2Y receptor, which is easily studied. On the other hand, the P2X1 receptor was not thought to play a major role in platelet activation, and it proved very troublesome to study since it became desensitized once blood is drawn from the body, Spence said.

Though scientists tried a pair of methods to get around that issue – by using different additives or enzymes – the results did not prove fruitful in studying the receptor.

What Spence and his team found is that by adding a simple molecule called NF449 – originally thought to block the receptor – they were able to activate the P2X1 receptor in platelets after a blood draw.

"We have discovered a way to prepare and handle platelets so that we can study the receptor authentically," he said. "This research opens up new avenues of study and will allow researchers and pharmaceutical companies to re-appraise this receptor as a druggable target."

More information: The research paper can be found at Analytical Methods at http://pubs.rsc.or … y/c1ay05530e

Provided by Michigan State University (news : web)

Scientists unlock mystery of how the 22nd amino acid is produced

The most recently discovered amino acid, pyrrolysine, is produced by a series of just three chemical reactions with a single precursor – the amino acid lysine, according to new research.

Scientists at Ohio State University used mass spectrometry and a series of experiments to discover how cells make the amino acid, a process that until now had been unknown.

They confirmed that pyrrolysine is made from enzymatic reactions with two lysine molecules – a surprising finding, given that some portions of its structure suggested to researchers that it might have more complex origins.

The research is published in the March 31 issue of the journal Nature.

Pyrrolysine is rare and so far is known to exist in about a dozen organisms. But its discovery in 2002 as a genetically encoded amino acid in methane-producing microbes raised new questions about the evolution of the genetic code. Pyrrolysine is among 22 amino acids that are used to create proteins from the information stored in genes. Proteins are essential to all life and perform most of the work inside cells.

This information about how it is produced – its biosynthetic pathway – offers a more complete understanding of how amino acids are made. And because of its rarity, this molecule is emerging as a handy tool for manipulating proteins in biomedical research. With its production mechanism identified, scientists can use that information to devise ways to mass-produce similar or identical synthetic molecules for a variety of research purposes.

The Ohio State scientists had a genuine "ah-ha" moment over the course of the study. As part of their experimentation, they combined lysine with one other amino acid and some enzymes and expected this to produce what is called an intermediate – essentially, a piece of an amino acid that is generated in the biosynthesis process.

They had labeled the lysine so it would appear heavier than normal when observed using mass spectrometry. But one signal produced by the instrumentation had a much different mass than could be attributed to the intermediate.

"We weren't seeing this weird molecule made from two different amino acids that we were expecting. We were seeing the regular pyrrolysine molecule and all of it was coming from lysine. Every bit of it," said Joseph Krzycki, professor of microbiology at Ohio State and senior author of the study. "That was the only way we saw pyrrolysine, and all of it was labeled with lysine. That's the basic observation here. And it's a real surprise."

The finding that lysine was the only precursor was a surprise because the production process ended up being so simple – even though arriving at it was not a simple task, partly because some of the chemical reactions had never been observed before.

"What amazes me about the entire chemical pathway is that you need only three enzymes and two molecules of the same thing that together make one complete molecule that looks completely different from what you started with," said Marsha Gaston, first author of the paper and a doctoral student in microbiology. "You have one portion that looks exactly like the precursor, but then you have another portion that enzymes are able to re-arrange in a way that is completely unique and never seen before."

Mass spectrometry, an analytic technique that enables precision in determining the mass of particles, ended up being critical to the discoveries, Krzycki noted. Liwen Zhang and Kari Green-Church of Ohio State's Campus Chemical Instrument Center/Mass Spectrometry and Proteomics Facility are additional co-authors of the study.

Krzycki led one of the two teams of Ohio State researchers that discovered pyrrolysine in 2002. The teams have since synthesized the amino acid and shown how bacteria incorporate it into proteins.

"That left some big questions unanswered: How do you make pyrrolysine? Where does it come from? What metabolic pathways does it come off of? Because it's got to be generated within the cell that uses it," Krzycki said.

The chemical shape of pyrrolysine offered some clues. Its carbon skeleton resembles that of lysine. But it also has an unusual ring on one end, and a methyl group attached to it, which for researchers raised questions about its origin.

The researchers also knew from their previous work that three genes are required to generate the instructions for the assembly of proteins that contain pyrrolysine – pylB, pylC and pylD. So the enzymes produced by those three genes had to have a role in creation of the amino acid. Finally, previous attempts by other researchers to define its biosynthesis suggested that another amino acid, D-ornithine, was involved in pyrrolysine's production.

So Krzycki and his colleagues set out to test that theory. Conducting all of their experiments in a strain of E. coli bacteria, commonly used to test biological functions, they combined lysine and D-ornithine molecules.

They found that this didn't make pyrrolysine, but rather a molecule like pyrrolysine that was missing a key part; however, this molecule turned out not to be converted to pyrrolysine. This molecule also was formed without the involvement of pylB – a gene that could not be left out of the process that actually makes pyrrolysine.

With the mass spectrometry instead identifying lysine as the only precursor to pyrrolysine, the researchers then used genetics, mass spectrometry of intermediates and deduction to determine the order of enzymatic reactions that converted two lysine molecules into the pyrrolysine amino acid.

They determined that the sequence of events matched the alphabetical order of the three involved enzymes: PylB uses lysine to make a D-ornithine-like intermediate, PylC joins the two lysine molecules together, and that feeds a reaction involving PylD that results in the formation of pyrrolysine. The reactions showed how the ring on pyrrolysine's end, its major identifying characteristic, is formed.

"If you splay out the pyrrolysine molecule, you can recognize that in fact it looks a lot like lysine, except that to get to this ring, you have to make the second molecule one carbon unit shorter," Krzycki said. "The lysine goes through a type of enzymatic reaction called a mutase reaction, where the carbon skeleton is rearranged to make this shorter molecule, which is like D-ornithine, but with one extra carbon now hanging off the chain in a new place. That's what one of our pyrrolysine biosynethetic enzymes, PylB, is doing."

Krzycki noted that this finding will add fuel to discussions of how the genetic code evolved. For example, the co-evolutionary theory suggests that amino acids arising from a common precursor have similar codon assignments. Codons are three-letter "words" identifying the bases that DNA uses to specify particular amino acids as building blocks of proteins. Normally, codons signal the start or end of a protein, or a particular amino acid used to construct it.

"For the scientists who are devoted to exploring how the genetic code evolved, our data provides new insights that can feed the various theories for how the code evolved; the co-evolutionary theory is just one such example," Krzycki said.

The finding that pyrrolysine derives entirely from lysine means that pyrrolysine is part of the aspartic acid family in bacteria and Archaea, a group of single-cell microorganisms that are similar to bacteria in size and shape, but with a different evolutionary history. The microbes known to contain pyrrolysine are in the Archaea domain, and are able to convert a common class of compounds – the methylamines – into methane gas.

Provided by The Ohio State University (news : web)

Atom-thick sheets unlock future technologies

A new way of splitting layered materials, similar to graphite, into sheets of material just one atom thick could lead to revolutionary new electronic and energy storage technologies.

An international team, led by Oxford University and Trinity College Dublin scientists, has invented a versatile method for creating these one-atom thick 'nanosheets' from a range of materials using mild ultrasonic pulses, like those generated by jewellery cleaning devices, and common solvents. The new method is simple, fast, and inexpensive, and could be scaled up to work on an industrial scale.

The team publish a report of the research in this week's Science.

Each one-millimetre-thick layer of graphite is made up of around three million layers of graphene -- a flat sheet of carbon one atom thick -- stacked one on top of the other.

'Because of its extraordinary electronic properties graphene has been getting all the attention, including a recent Nobel Prize, as physicists hope that it might, one day, compete with silicon in electronics,' said Dr Valeria Nicolosi of Oxford University's Department of Materials, who led the research with Professor Jonathan Coleman of Trinity College Dublin. 'But in fact there are hundreds of other layered materials that could enable us to create powerful new technologies.'

Professor Coleman, of Trinity College Dublin, said: 'These novel materials have chemical and electronic properties which are well suited for applications in new electronic devices, super-strong composite materials and energy generation and storage. In particular, this research represents a major breakthrough towards the development of efficient thermoelectric materials.'

There are over 150 of these exotic layered materials -- such as Boron Nitride, Molybdenum disulfide, and Tungsten disulfide -- that have the potential to be metallic, semi-metallic or semiconducting depending on their chemical composition and how their atoms are arranged.

For decades researchers have tried to create nanosheets of these kind of materials as arranging them in atom-thick layers would enable us to unlock their unusual electronic and thermoelectric properties. However, all previous methods were extremely time consuming and laborious and the resulting materials were fragile and unsuited to most applications.

'Our new method offers low-costs, a very high yield and a very large throughput: within a couple of hours, and with just 1 mg of material, billions and billions of one-atom-thick graphene-like nanosheets can be made at the same time from a wide variety of exotic layered materials,' said Dr Nicolosi.

Nanosheets created using this method can be sprayed onto the surface of other materials, such as silicon, to produce 'hybrid films' which, potentially, enable their exotic abilities to be integrated with conventional technologies. Such films could be used to construct, among other things, new designs of computing devices, sensors or batteries.

The work was conducted by a team including scientists from Oxford University, Trinity College Dublin, Imperial College London, Korea University, and Texas A&M University (USA).

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Oxford.

Journal Reference:

J. N. Coleman, M. Lotya, A. O'Neill, S. D. Bergin, P. J. King, U. Khan, K. Young, A. Gaucher, S. De, R. J. Smith, I. V. Shvets, S. K. Arora, G. Stanton, H.-Y. Kim, K. Lee, G. T. Kim, G. S. Duesberg, T. Hallam, J. J. Boland, J. J. Wang, J. F. Donegan, J. C. Grunlan, G. Moriarty, A. Shmeliov, R. J. Nicholls, J. M. Perkins, E. M. Grieveson, K. Theuwissen, D. W. McComb, P. D. Nellist, V. Nicolosi. Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials. Science, 2011; 331 (6017): 568 DOI: 10.1126/science.1194975