Nanodiamantes podem melhorar o tratamento de cânceres resistentes

Pequena partícula de carbono chamada nanodiamante poderia significar uma alternativa eficaz para levar o remédio aos tumores de difícil tratamento

Nanodiamantes ganham marcação fluorescente verde

WASHINGTON - A resistência que o câncer desenvolve à quimioterapia contribui com mais de 90% dos casos de metástase, mas a adição de diamantes que medem um milésimo de milímetro poderia melhorar o tratamento, segundo um artigo publicado nesta quarta-feira pela revista Science Translational Medicine.

Dean Ho, professor de engenharia biomédica e mecânica da Universidade Northwestern, em Chicago, acredita que a pequena partícula de carbono chamada nanodiamante poderia significar uma alternativa eficaz para levar o remédio aos tumores de difícil tratamento.

Os nanodiamantes são materiais com base de carbono de 2 a 8 nanômetros de diâmetro (um nanômetro é um bilionésimo de metro).

Ilustração mostra nanodiamantes entrando na corrente sanguínea

A superfície de cada nanodiamente possui grupos funcionais que permitem que sejam adicionados a ele uma ampla gama de compostos, incluindo os agentes da quimioterapia.

Os pesquisadores tomaram esses nanodiamantes e ligaram a eles o composto doxorrubicina, que é normalmente usado na quimioterapia, utilizando um processo de síntese, que realça a liberação sustentada do composto.

Em seus estudos de câncer de fígado e de mama, Ho e sua equipe de cientistas, engenheiros e clínicos descobriram que uma quantidade normalmente letal de compostos de quimioterapia reduz o tamanho dos tumores em ratos, quando aplicado em conjunto com os nanodiamantes.

Também melhoram as taxas de sobrevivência e não foram observados efeitos colaterais nos tecidos e órgãos.

Segundo o artigo, este é o primeiro trabalho que demonstrou o significado e o potencial dos nanodiamantes no tratamento de cânceres que se tornaram resistentes à quimioterapia.

Cientistas descobrem causador da inflamação que mata neurônios

Cientistas espanhóis e suecos descobriram a ligação molecular desencadeante da inflamação cerebral que mata os neurônios, um processo muito associado a doenças neurodegenerativas, como Prkinson e Azheimer, segundo a última edição da revista "Nature".

Equipes da Universidade de Sevilha e do Instituto Karolinska de Estocolmo, dirigidas pelos médicos José Luis Venero e Bertrand Joseph, e em colaboração com pesquisadores da Universidade de Lund, encontraram um mecanismo responsável pelo processo da neuroinflamação.

O doutor Venero, do departamento de Bioquímica e Biologia Molecular da Faculdade de Farmácia da Universidade de Sevilha, indicou que este estudo pode abrir novos caminhos farmacológicos para o controle da inflamação cerebral e seus efeitos nocivos.

A pesquisa de quase quatro anos de duração incluiu a histologia e anatomia microscópica de áreas corticais e do mesencéfalo ventral de cérebros de pacientes que morreram de Alzheimer ou Parkinson, assim como culturas de células e modelos experimentais em ratos e camundongos com doença de Parkinson.

Os dados experimentais foram transferidos para situações de inflamação cerebral pela associação com as doenças de Parkinson e Alzheimer.

Embora não seja possível confirmar que a inflamação é o fator desencadeante das doenças neurodegenerativas, sabe-se que está muito associada ao Parkinson e ao Alzheimer, segundo o doutor Venero.

De fato, os pesquisadores começam a admitir "de forma generalizada" a ideia de que uma resposta inflamatória contribui "decisivamente" para a progressão das doenças neurodegenerativas.

Os pesquisadores descobriram neste trabalho uma nova função biológica de algumas enzimas caspases (associadas tradicionalmente apenas aos processos de apoptose ou morte celular programada) que são necessárias, por exemplo, em situações de regeneração celular e em resposta para danos neuronais e agentes patógenos.

A nova função destas proteínas se refere ao controle da atividade de algumas células microgliais, hospedadas no sistema nervoso central, responsáveis pela resposta imune e pelo processo de inflamação cerebral que mata os neurônios.

Concretamente, ficou comprovado que o controle da ativação ordenada da caspase 8 e da caspase 3 está relacionado com o início de um processo de sinalização celular que leva à ativação das células microgliais.

Foi verificado que a inibição dessas enzimas por métodos farmacológicos ou moleculares diminui a capacidade das células microgliais de se ativar em resposta a estímulos inflamatórios.

Os cientistas sabiam da ativação destas células frente a problemas neuronais ou agentes patógenos para "orquestrar" a resposta imune e iniciar a reparação do tecido danificado, mas a atual descoberta mostra que a ativação persistente libera moléculas nocivas para os neurônios, como ocorre no Alzheimer e no Parkinson.

Os cérebros estudados revelaram uma clara ativação tanto de enzimas caspase 8 como de caspase 3 nas células microgliais desencadeantes de processos de inflamação cerebral, com a peculiaridade de que apenas o citoplasma foi afetado, e não o núcleo celular.

Os pesquisadores concluem que os inibidores de caspases poderiam ser utilizados para o controle da inflamação cerebral.

Cientistas desvendam segredo de erva medicinal chinesa

Cipó deus do trovão

Os produtos naturais da medicina tradicional chinesa vêm funcionando há milênios.

O que os cientistas querem descobrir é como eles funcionam - isolando os princípios ativos, pode ser possível potencializar seus efeitos, controlando doses para tratamentos mais críticos.

Agora foi a vez da erva conhecida como cipó deus do trovão, ou lei gong teng, ter seus segredos revelados.

O lei gong teng é usado para tratar várias condições, com efeitos anti-inflamatórios, imunossupressores, atividades antitumorais e até anticoncepcionais.

Drogas anticâncer

Segundo pesquisadores da Escola de Medicina Johns Hopkins, dos EUA, a planta medicinal chinesa funciona bloqueando os mecanismos de controle genético da célula.

A pesquisa, que mereceu a matéria de capa da edição de Março da revista Nature Chemical Biology, sugere que o produto natural pode ser um ponto de partida para o desenvolvimento de novas drogas anticâncer.

"Nós sabíamos sobre o composto ativo, a triptolida, e que ele pára o crescimento celular, desde 1972, mas só agora descobrimos como ele faz isso," conta o Dr. Jun O. Liu, coordenador da pesquisa.

Triptolida

A triptolida, o ingrediente ativo purificado da planta Tripterygium wilfordii Hook F, já teve seus efeitos demonstrados contra a artrite, o câncer e a rejeição do enxerto de pele.

Na verdade, segundo Liu, já se demonstrou em modelos animais que a triptolida, em doses muito baixas, bloqueia o crescimento de todas as 60 linhas celulares catalogadas pelo Instituto Nacional do Câncer dos Estados Unidos, inclusive destruindo algumas dessas linhas de células.

Outros experimentos têm sugerido que a triptolida interfere com proteínas conhecidas para ativar genes, o que deu a Liu e seus colegas um ponto de partida para suas pesquisas.

Proteína XPB

Os pesquisadores descobriram que a proteína XPB, de um aglomerado de proteínas chamado TFIIH, tem sua atividade enzimática bloqueada pelo composto ativo da planta medicinal chinesa, interrompendo quase imediatamente a fabricação de RNA novo nas células tumorais.

"Estávamos quase certos de que era mesmo a XPB porque outros pesquisadores tinham descoberto que a triptolida se liga a uma proteína desconhecida do mesmo tamanho, mas eles não foram capazes de identificá-la", disse Liu.

Com a proteína identificada, os cientistas podem agora estudar como o composto natural funciona em cada situação na qual ele é eficaz.

Molecule That Can Increase Blood Flow in Vascular Disease Identified

ScienceDaily (Mar. 10, 2011) — Circulating through the bloodstream of every human being is a rare and powerful type of cell, one that can actually create new blood vessels to bypass blockages that cause heart attacks and peripheral artery disease. Though everyone has these cells -- called endothelial progenitor cells -- they are often dysfunctional in people prone to vascular disease.

Human endothelial progenitor cells grown in the lab (left) and forming capillary tube like structures (right).

Now researchers at the University of North Carolina at Chapel Hill have discovered that a molecule -- called Wnt1 -- can improve the function of endothelial progenitor cells, increasing the blood flow to organs that previously had been cut off from the circulation. The finding could enhance clinical trials already testing these powerful cells in patients hospitalized with cardiac arrest.

"The premise of these trials is that these cells will supply the ischemic organ with new blood vessels and allow the damaged organ to function better," said senior study author Arjun Deb, MD, assistant professor of medicine in the UNC School of Medicine. "But because you are isolating these cells from the patients themselves, you know that the cells are dysfunctional -- so the approach is almost flawed from the very beginning. We want to see how we can improve the function of these cells so they can do their job better."

The study, published online Feb. 14, 2011, in the FASEB (Federation of American Societies for Experimental Biology) Journal, is the first to show that the Wnt1 protein, one of a family of 19 such molecules, can stimulate blood vessel formation.

A number of studies in the past few years have suggested that genes that play an important role during early development and get "turned off" during adulthood may also get "turned on" or expressed again in response to injury, such as heart attack.

Deb, who studies the Wnt family of developmental genes, looked to see if any of its members follow this same pattern. He found that one gene in particular, Wnt1, was expressed during development of blood vessels, shut off during adulthood and then re-expressed in angiosarcoma, a cancer of endothelial cells.

Deb wanted to see what would happen if he put the Wnt1 protein on human endothelial progenitor cells. He found that treating these special cells with Wnt1 not only greatly increased their function but also their number. Next, Deb and his colleagues investigated what effect the protein would have on a mouse model of peripheral artery disease, an illness in humans caused by decreased blood flow to the extremities. They found that treating these animals with a single injection of the Wnt1 protein resulted in almost three fold increase in blood flow in the affected areas.

"We found that Wnt1 is a novel proangiogenic molecule, something that has never been shown before," said Deb. "It gives us hope that injecting the Wnt1 protein -- or molecules that stimulate the Wnt1 signaling pathway -- into ischemic tissues in humans could improve blood flow and assert a therapeutic effect."

Approximately 1 in 4 deaths in adults in the US are secondary to heart disease and as many as 15 percent of Americans age 65 and older have peripheral artery disease. In the future, Deb plans to use his findings to identify such small molecules or drug candidates that could reverse the endothelial progenitor cell dysfunction observed in so many patients with vascular disease.

The research was funded by the National Institutes of Health and Ellison Medical Foundation. Study co-authors were Costin M. Gherghe, MD, PhD, postdoctoral fellow in Deb's lab; Jinzhu Duan, PhD, postdoctoral fellow in Deb's lab; Jucheng Gong, lab manager in Deb's lab; Mauricio Rojas, MD, MPH, director of mouse cardiovascular models core lab; Nancy Klauber-Demore, MD, associate professor of surgery; and Mark Majesky, PhD, Professor of Pediatrics, University of Washington, Seattle.

How Inherited Genes Contribute to a Common, Incurable Neurodegenerative Disease

ScienceDaily (Mar. 10, 2011) — A team of scientists at the University of California, San Francisco (UCSF) has developed a new model for how inherited genes contribute to a common but untreatable and incurable neurodegenerative disease. The disease, frontotemporal lobar degeneration, is the second most common cause of dementia before age 65, after Alzheimer's disease.

Progranulin-deficient macrophages after engulfing flourescently labelled beads.

Based on experiments in worms and mice, the UCSF team's work explains in part why the brain deteriorates in frontotemporal lobar degeneration, which may have implications for the understanding of several neurodegenerative disorders, including Alzheimer's and Parkinson's, as well as different forms of cancer.

"If our findings hold up," said Aimee Kao, an assistant adjunct professor in the Department of Neurology at UCSF, "they may suggest a new way to think about how to treat neurodegenerative diseases." Kao is first author on the study, led by Cynthia Kenyon, PhD, a professor of biochemistry and biophysics at UCSF and director of UCSF's Larry L. Hillblom Center for the Biology of Aging.

Disease Caused By Loss of Neurons

Generally scientists have blamed the mental decline associated with neurodegenerative diseases on the loss of neurons associated with the accumulation of insoluble protein in the brain -- sticky plaques that interfere with and ultimately kill the brain's neurons.

In frontotemporal lobar degeneration, this loss of neurons happens in the frontal lobe -- the part of the brain involved in such higher mental functions as art appreciation and emotional empathy. People with this disease can suffer from progressive difficulties with language, undergo personality and behavioral changes, and usually die within a decade of diagnosis.

The new work suggests that the accumulation of insoluble protein may not be the only cause of cognitive decline in frontotemporal lobar degeneration. Another mechanism could involve how the body deals with injured neurons in the brain.

A significant percentage of patients with frontotemporal lobar degeneration have mutations in the gene that produces a protein called progranulin. Scientists have known that people with these genetic mutations produce too little progranulin protein, but up to now it was unclear what role this played in disease development.

Now the work of the UCSF team suggests that progranulin regulates the speed with which dying cells are cleared.

The Speed of Brain Cell Death

Cells in the brain -- as in the rest of the human body -- die through a process known as apoptosis, or programmed cell death. In a sense, apoptosis is the cellular equivalent of a controlled implosion.

Rather than explode a condemned building in a crowded city and scatter its dust and rubble across surrounding neighborhoods, implosions minimize the fallout. Likewise, apoptosis of neurons prevents them from exploding and damaging the surrounding brain tissue, instead withering them away in protective fashion.

In their paper, Kao, Kenyon and their colleagues show that progranulin normally slows the process of apoptosis. In its absence, however, apoptotic cells are cleared more quickly, probably by neighboring cells, which engulf them.

Using a sophisticated microscope, the UCSF team showed that mutations to the progranulin gene caused cells in the microscopic roundworm C.elegans that were undergoing this programmed cell death to be cleared in about half the time, as compared to normal worms. They also found something similar in engulfing cells called macrophages that were taken from mice. When these cells lacked progranulin, they engulfed other, dying cells even faster.

"In both worms and cultured macrophages," Kao said, "the absence of progranulin cause more rapid clearance of dying cells."

Based on these findings, the team hypothesized that lack of progranulin may affect the ability of cells to recover from an injury. When individual cells are injured, the damage may or may not be fatal. Given enough time, the damaged cell could recover. However, if local engulfing cells are over-eager to remove the damaged cell, the cell may have too little time to recover. If this scenario occurred in the brain, then over time, the cumulative cell loss could lead to neurodegenerative disease.

These findings also have implications in the treatment of cancer, since some aggressive forms of breast, brain and bladder cancer produce increased levels of progranulin.

"These cancers may be using progranulin as a sort of 'invisibility shield' to hide from the surveillance of the immune system," Kao said. "Thus, progranulin could represent a druggable target in both neurodegeneration and some forms of cancer."

The study was published online in the journal Proceedings of the National Academy of Sciences.

Molecules Work the Day Shift to Protect the Liver from Accumulating Fat

ScienceDaily (Mar. 10, 2011) — The liver normally makes and stores fat, which is required in moderation for normal body function. However, if the process goes awry, excess fat in the liver can cause major liver damage. In fact, fatty liver is a leading cause of liver failure in the United States, and is often brought on by obesity and diabetes. In turn, the increasing prevalence of these diseases has brought with it an epidemic of liver disease.

Depletion of liver HDAC3 causes fatty liver in normal adult mice. Liver tissue lacking HDAC3 (top image; fat is stained red). Liver with normal HDAC3 levels (bottom image).

Abnormal sleep patterns, such as those of shift-workers, can be risk factors for obesity and diabetes. Investigators have known for decades that fat production by the liver runs on a 24-hour cycle, the circadian rhythm, and is similar to the sleep-wake cycle. A research team led by Mitchell Lazar, MD, PhD, director of the Institute for Diabetes, Obesity, and Metabolism at the University of Pennsylvania School of Medicine, has discovered molecules that act as "shift workers" to maintain the daily rhythm of fat metabolism. When those molecules do not do their jobs, the liver dramatically fills with fat. These findings are reported in this week's issue of Science.

Lazar and his colleagues, including Cell and Molecular Biology graduate student Dan Feng, found a team of molecules that, in normal mice, migrates to the genome of liver cells during the daytime. One of the team members, a protein called Rev-erb, delivers the molecular workers to thousands of specific locations in the liver genome, many of which are near genes involved in the production of fat. Another team member, called histone deacetylase 3 (HDAC3), does construction work on the protein scaffold (the epigenome) surrounding the genome to dampen the activity of the fat-related genes.

"This work shows that the epigenome, which is critical for regulating how genes are expressed, undergoes reversible remodeling every day," said Lazar. "This leads to a circadian rhythm of metabolism that is important, because disruption of this rhythm leads to fatty liver. This may explain in part why altered circadian rhythms in people who do shift work is associated with metabolic disorders."

Histones are proteins found in the nucleus that package and order DNA into structural units. Changes to these epigenetic structures alter how DNA folds in chromosomes, making genes less or more accessible to regulatory proteins and enzymes that copy genes into RNA messages.

Construction Team

During the night, the day shift molecules depart the liver genome, and fat production increases due to other regulatory molecules. The fat production is kept in check when the Rev-erb construction team returns to the genome the next day. However, if either Rev-erb or HDAC3 is prevented from doing its job, the cycles do not occur, and the liver fills with fat.

By sequencing the DNA associated with HDAC-3 in the liver the Penn team found HDAC in 100 places in the liver genome at 5:00am, but 12 hours later at 5:00pm, HDAC was present in 15,000 places in the liver genome, indicating that it had been brought to the liver during the day. They also found that Rev-erb follows the same daily pattern, because it is the protein that gives HDAC-3 a ride to work.

The Lazar lab is looking in other tissues -- fat cells, muscle, for example -- to see if the same team of molecules is at work, as well as delving deeper into human applications to see how the findings may help explain what goes wrong with fat production and storage in conditions such as metabolic syndrome, insulin resistance, and diabetes. These findings also raise the interesting question of whether certain drugs should be given at specific times of day, to have greater benefit with reduced side-effects.

In addition to Lazar and Feng, Penn co-authors are Zheng Sun, Shannon Mullican, and Theresa Alenghat. The study was a collaboration with Tao Liu and X. Shirley Liu, at the Dana-Farber Cancer Institute in Boston. The National Institute of Diabetes, Digestive, and Kidney Diseases provided funding for this research.

New Clues to Help Patients With Immune Deficiency Disease

ScienceDaily (Mar. 10, 2011) — Infection researchers at Umeå University have uncovered a new disease mechanism in patients with Chronic Granulomatous Disease (CGD) in an international clinical collaboration with the Children's Hospital in Zurich.

Scanning electron microscopy of neutrophils infected with Aspergillus nidulans. The neutrophils are from the same patient before and after gene therapy. Before treatment the neutrophils are unable to form extracellular traps and after therapy this ability is restored.

Their new findings are published in the Journal of Allergy and Clinical Immunology.

Fungal infections can cause life-threatening health problems for patients with immune deficiency. Their health is weakened by infections and they cannot undergo the treatment or surgery they need to survive. An example is Aspergillus infection which is life threatening for these patients. In this condition, the immune system is not able to kill the pathogen and the mould propagates from the lungs and respiratory tract into the whole body.

Chronic Granulomatous Disease (GDC) is a heritable severe immune deficiency disease that occurs at a frequency of one in 200,000 humans per year worldwide. Children with CGD often suffer life-threatening microbial infections with bacteria and fungi and die at young age without treatment. Particularly, infections with Aspergilli fungi often kill CGD patients, before bone marrow transplantations or gene therapy can be performed.

Scientists at the Swedish Laboratory for Molecular Infection Medicine (MIMS) in Umeå have now found new treatment of CGD patients.

While healthy individuals' white blood cells, also called neutrophils, release oxygen intermediates to kill and digest invading pathogens, the immune cells in CGD patients lack the ability to kill the microbes.

Constantin Urban, research group leader at the MIMS laboratory in Umeå is studying mechanisms of fungi infections. In earlier studies of Candida infections, he found with his colleagues that neutrophils form extracellular structures, called neutrophil extracellular traps or NET, which catch microbes and fungi.

"NET is a very smart tool," says Urban. "It is comparable with a spider's web, catching and killing the trapped pathogen. We found in earlier studies that these web-like structures are made of chromatin and decorated with antimicrobial proteins. They also release oxygen intermediates and an antifungal substance called calprotectin."

In collaboration with clinical researchers at the Children's Hospital in Zurich, the scientists from Umeå found new details behind CGD. They compared the function of a CGD patient's neutrophils before and after gene therapy.

"Our results clearly show that calprotectin is also important for the neutrophils immune defence against Aspergillus infection," says Constantin Urban.

Together with PhD student Maria Joanna Niemiec in his group at MIMS and medical doctors in Zurich, Constantin Urban found that neutrophils from the CGD patient did not form NETs trap and were not able to release calprotectin. This was the reason why the neutrophils were not able to kill and digest Aspergillus cells anymore.

"We found that after gene therapy the neutrophils could produce calprotectin at a normal level and even the NET structure was formed again," says Maria Joanna. "Our experiment showed that calprotectin is a key player for the neutrophils' defence against Aspergillus infection. We are now convinced that calprotectin can be used as a "molecular support" to compensate the neutrophils cell defect in CGD patients."

"We are confident that our study may lead to new treatment of CGD patients in the beginning of their life and prevent them from infections until they have the possibility to receive gene therapy or bone marrow transplantation, which are more sustainable treatments," says Constatin Urban. "This possible treatment for CGD patients may also be an opportunity in the future for patients with other immune deficiency diseases."

Why Low Birth Weight Is Linked to Obesity Later in Life: Study Provides Explanation

ScienceDaily (Mar. 10, 2011) — Providing further understanding of the link between low birth weights and obesity later in life, researchers found nutritionally deprived newborns are "programmed" to eat more because they develop less neurons in the region of the brain that controls food intake, according to an article published in the journal Brain Research.

LA BioMed study finds nutritionally deprived newborns are “programmed” to eat more because they develop less neurons in the region of the brain that controls food intake.

The study by a team of researchers at Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center (LA BioMed) suggests that overeating is programmed at the level of stem cells before birth when the mother has poor or inadequate nutrition.

Using an animal model, the researchers found less division and differentiation of the neural stem cells of a newborn with low birth weight as compared to normal birth weight. Previous studies have found a small size at birth followed by accelerated "catch-up" growth is associated with an increased risk of adult obesity, cardiovascular disease, type 2 diabetes, hypertension and osteoporosis.

"This study demonstrates the importance of maternal nutrition and health in reducing obesity," said Dr. Mina Desai, an LA BioMed principal investigator and corresponding author of the new study. "Obesity and its related diseases are the leading cause of death in our society, yet we have few effective strategies for prevention or treatment. These studies suggest maternal nutrition could play a critical role in preventing obesity and related disease."

In addition to obesity, the findings of altered brain (neural stem cells) development suggest that fetal growth restriction may be associated with cognitive and/or behavioral alterations. Importantly, the study offers potential opportunities for prevention and treatment for obesity and other related disorders. In addition to Dr. Desai, LA BioMed investigators Tie Li and Michael G. Ross participated in the study.

More than 60% of American adults are overweight and more than 1 in 5 are obese. Obesity is a serious health concern for children and adolescents, as well. About 17 percent of children and adolescents ages 2-19 years are obese.

New Details About Medically Important Protein Family

ScienceDaily (Mar. 10, 2011) — Scientists from The Scripps Research Institute have determined a new structure from a medically important superfamily of proteins. The structure should help instruct the design of a new kind of therapeutics for conditions ranging from Parkinson's disease to inflammation.

The new study reveals the structure of the human A2A adenosine receptor, a member of the GPCR family sometimes referred to as the “caffeine receptor,” bound to a full agonist. 

The study, published on March 10, 2011, in Science Express, an advance, online publication of selected research from the journalScience, provides important insights into how this large family of proteins, called G protein-coupled receptors (GPCRs), can recognize and respond to a wide array of signals, including odors, hormones, neurotransmitters, and light.

Many drugs, including allergy and heart medication and drugs for Parkinson's and Huntington's disease, target GPCRs, a family of proteins that comprises some 700 to 1,000 members.

A Surprisingly Stable Active Form

GPCRs sit in the cell membrane and sense various molecules outside cells. When certain molecules bind to them, the receptor's structure shifts so that it transmits its signal within the cell. These receptor-activating molecules are referred to as agonists. But GPCRs can also bind "antagonists," compounds that block the receptors' activity by preventing agonists from binding.

Up until now, researchers had primarily been able to obtain the structures of GPCRs bound to antagonists -- in other words, in their inactive but more stable forms. Some scientists thought a receptor bound to an agonist would be too dynamic without stabilizing mutations or G-proteins bound for the receptor to be amenable to forming crystals, a critical step required for determining protein structures using the technique of X-ray crystallography.

In the new study, Fei Xu, a graduate student in the Stevens lab and the first author of the paper, proved these assumptions inaccurate.

The Stevens lab obtained the structure of the human A2A adenosine receptor, a member of the GPCR family sometimes referred to as the "caffeine receptor," bound to a full agonist. The team discovered that when the receptor bound to this particular agonist, it took on a new shape, as expected, but it then remained in that new conformation, rather than continuing to move.

"We were surprised to discover a super stabilizing agonist," said Stevens. "While dynamics is certainly a critical component of receptor signaling, it is not as extreme or the complete story as previously thought. The agonist we solved with the A2A structure highlights the fact that certain agonists can stabilize the receptor in a single conformation without the presence of an intracellular binding partner such as a G-protein. This is also teaching us that what we learn from one receptor or one agonist/antagonist interaction should not necessarily be a rule for all GPCRs at this early stage of GPCR structure discovery. We need to study multiple systems in-depth before we will really understand this receptor family."

The finding has important implications for drug design. In some diseases, such as Parkinson's disease, potential treatments involve blocking the functions of certain GPCRs using antagonists. But for treating other diseases such as COPD, researchers are trying to develop agonists that activate GPCRs. This new finding could facilitate the design of such agonist-based drugs.

Ward Smith, director of the National Institutes of Health (NIH) Protein Structure Initiative (PSI), which funded the study, said, "Determining the structure of the active form of the A2A adenosine receptor represents just the kind of significant accomplishment that the Protein Structure Initiative was intended to foster. Now that we know what the active form looks like, we have a much better idea of how this important class of cellular gatekeepers functions and how we might manipulate their activity in treating disease."

Decades-Long Vision Yields Results

Stevens began working on the structures of GPCRs more than two decades ago. His group in collaboration with researchers at Stanford University solved the first human GPCR structure, the β2 adrenergic receptor, in 2007 -- a project that took 17 years to complete. Since then the Scripps Research team has been successful in obtaining several other GPCR structures in collaboration with other laboratories around the world.

"The reason we have now solved several human GPCR structures is the strong and robust scientific platform we built at Scripps with NIH support," says Stevens, who is director of the NIH Common Fund Joint Center for Innovative Membrane Protein Technologies, focused on developing and disseminating technologies, and the National Institute of General Medical Sciences PSI:Biology GPCR Network, focused on increasing the knowledge of GPCR biology. "When the NIH funded this research they took a very big chance on high risk/high reward science and it is now paying off in multiple ways from new technologies to new biological insight."

Like all proteins, GPCRs consist of long chains of amino acids that assemble themselves in three-dimensional shapes. GPCRs consist of seven helices that span the membrane of a cell. Loops connecting the helices sit both outside the cell membrane and inside the cell.

In the new study, Stevens and colleagues found that when the agonist bound the A2A receptor, helices 5, 6 and 7 underwent a dramatic shift in their positions. In contrast, helices 1 to 4 tended to stay relatively still. "GPCRs appear to be composed of two domains," he explained. "The first four helices appear more rigid than the last three."

In addition, the portions of the receptor sitting outside the cell membrane shifted their positions to accommodate the agonist binding, whereas the segments on the inside of the cell had smaller changes.

The greater flexibility for the outside portions may hold the key for understanding GPCRs' ability to recognize and respond to molecules of many different sizes and shapes. This is reminiscent of how the immune system uses the antibody architecture to recognize so many different ligands.

"You need receptor diversity on the outside to recognize all the different ligands, but inside the cell, you need less diversity since the receptor signals via a smaller number of binding partners," said Stevens.

Novel Role Found for Calcium Channels in Pacemaker Cell Function

ScienceDaily (Mar. 10, 2011) — Pacemaker cells in the sinoatrial node control heart rate, but what controls the ticking of these pacemaker cells? New research by Angelo Torrente and his colleagues of the M.E. Mangoni group's, reveals, for the first time, a critical functional interaction between Cav1.3 calcium ion (Ca2+) channels and ryanodine-receptor (RyR) mediated Ca2+ signaling.

A mouse pacemaker cell initiates local Ca2+ releases in the diastolic phase. Red spots are the regions with maximal [Ca2+]i released.

The study also sheds light on a long-standing debate regarding the relative contributions of the 'funny current' generated by ion channels and the RyR dependent spontaneous diastolic Ca2+ release theory in determining heart rate.

The investigation by the research team compared pacemaker cells in normal mice with mutants that lacked the L-type Cav1.3 channels to contrast how they handled calcium. They found that the absence of Cav1.3 channels in sinoatrial node (SAN) cells reduced the frequency of Ca2+ transients, which determine the rate of cardiac muscle contraction. The Cav1.3 channels were also found to be important regulators of ryanodine-receptor dependent local calcium release in the diastolic pacemaker phase. Overall, their results show that local calcium release in SAN cells is tightly controlled by the Cav1.3 channels.

Defects in calcium channels controlling heart muscle function are known to cause heart failure, and this study reveals that Cav1.3 mutant mice also suffer from bradycardia and other cardiac arrhythmias.

"Our results clarify the role of Cav1.3 channels in pacemaker generation, and are a step towards using it as a target for drug therapy to treat heart dysfunction related to the sinoatrial node," says A. Torrente of CNRS in Montpellier, France, who was the lead author on the study.

Not only Cav1.3 channels are critical to the heart pacemaker cell function, they appear to be important to several other cellular mechanisms as well. In both humans and mice, Cav1.3 mutations have been linked to sinoatrial node dysfunction and deafness (or SANDD) syndrome. Cav1.3 channels are believed to play a role in pancreatic β-cell stimulation, and they may also serve as pacemaker channels in the central nervous system, playing a pathophysiological role in Parkinson's disease.

"A better understanding of these channels in SAN could help us to comprehend the mechanism of calcium release in many other tissues and disease conditions as well," says Torrente.

New H1N1 Mutation Could Allow Virus to Spread More Easily

ScienceDaily (Mar. 10, 2011) — In the fall of 1917, a new strain of influenza swirled around the globe. At first, it resembled a typical flu epidemic: Most deaths occurred among the elderly, while younger people recovered quickly. However, in the summer of 1918, a deadlier version of the same virus began spreading, with disastrous consequence. In total, the pandemic killed at least 50 million people -- about 3 percent of the world's population at the time.

H1N1 influenza virus. 

That two-wave pattern is typical of pandemic flu viruses, which is why many scientists worry that the 2009 H1N1 ("swine") flu virus might evolve into a deadlier form.

H1N1, first reported in March 2009 in Mexico, contains a mix of human, swine and avian flu genes, which prompted fears that it could prove deadlier than typical seasonal flu viruses. However, the death toll was much lower than initially feared, in large part because the virus turned out to be relatively inefficient at spreading from person to person.

In a new study from MIT, researchers have identified a single mutation in the H1N1 genetic makeup that would allow it to be much more easily transmitted between people. The finding, reported in the March 2 edition of the journal Public Library of Science (PLoS) One, should give the World Health Organization, which tracks influenza evolution, something to watch out for, says Ram Sasisekharan, senior author of the paper.

"There is a constant need to monitor the evolution of these viruses," says Sasisekharan, the Edward Hood Taplin Professor and director of the Harvard-MIT Division of Health Sciences and Technology. Some new H1N1 strains have already emerged, and the key question, Sasisekharan adds, is whether those strains will have greater ability to infect humans.

WHO labs around the world are collecting samples of human and avian flu strains, whose DNA is sequenced and analyzed for potential significant mutations. However, it's difficult, with current technology, to predict how a particular DNA sequence change will alter the structure of influenza proteins, including hemagglutinin (HA), which binds to receptors displayed by cells in the human respiratory tract. Now that this specific HA mutation has been identified as a potentially dangerous one, the WHO should be able to immediately flag any viruses with that mutation, if they appear.

Identifying this mutation is an important step because it is usually very difficult to identify which of the many possible mutations of the HA protein will have any impact on human health, says Qinghua Wang, assistant professor of biochemistry at Baylor College of Medicine. "These are exactly the types of mutations that we need to watch out for in order to safeguard humans from future disastrous flu pandemics," he says.

Pandemic

On June 11, 2009, about three months after the H1N1 virus first appeared, the World Health Organization declared a level 6 pandemic alert (the highest level). Nearly 5,000 H1N1 deaths were reported to the WHO, and more than 400,000 cases were confirmed, though the true number of cases is significantly higher because many countries stopped counting cases after the first few months of the outbreak, according to the WHO.

In July 2009, a team of researchers from MIT, led by Sasisekharan, and the Centers for Disease Control and Prevention reported in the journal Science that the H1N1 virus was much less easily passed from person to person than seasonal flu viruses and earlier pandemic flu viruses such as the second wave of the 1918 strain.

Sasisekharan and CDC senior microbiologist Terrence Tumpey had previously shown that a major factor in flu-virus transmissibility is the structure of the HA protein, which is found on the viral surface. The tightness of fit between HA and the respiratory cell receptor determines how effectively the virus infects a host.

The 2009 H1N1 strain, like the first wave of 1918 (known as the NY18 strain), does not bind efficiently. However, it took only one mutation of the NY18 virus' HA protein to become the much more virulent SC18 strain, which caused the second wave.

Viral evolution

In the new PLoS study, the MIT researchers focused on a segment of the HA protein that they have shown affects its ability to bind to respiratory cells. They created a virus with a single mutation in that region, which replaced the amino acid isoleucine with another amino acid, lysine. That switch greatly increased the HA protein's binding strength. They also found that the new virus spread more rapidly in ferrets, which are commonly used to model human influenza infection.

If such a mutant virus evolved, it could generate a "second wave" like the ones seen in 1918 and in 1957 (known as the "Asian flu"). "If you look at the history, it takes a very small change to these viruses to have a dramatic effect," Sasisekharan says.

The amino acid in question is located in a part of the viral genome prone to mutate frequently, because it is near the so-called antigenic site -- the part of the HA protein that interacts with human antibodies. Antigenic sites tend to evolve rapidly to escape such antibodies, which is why flu vaccine makers have to use new formulas every year. This year's vaccine included a strain of H1N1, which is still circulating around the world.

Aging Rates, Gender Gap in Mortality Similar Across All Primates

ScienceDaily (Mar. 10, 2011) — Humans aren't the only ones who grow old gracefully, says a new study of primate aging patterns.

Capuchin monkey in Costa Rica.

For a long time it was thought that humans, with our relatively long life spans and access to modern medicine, aged more slowly than other animals. Early comparisons with rats, mice, and other short-lived creatures confirmed the hunch. But now, the first-ever multi-species comparison of human aging patterns with those in chimps, gorillas, and other primates suggests the pace of human aging may not be so unique after all.

The findings appear in the March 11 issue of Science.

You don't need to read obituaries or sell life insurance to know that death and disease become more common as we transition from middle age to old age. But scientists studying creatures from mice to fruit flies long assumed the aging clock ticked more slowly for humans.

We had good reason to think human aging was unique, said co-author Anne Bronikowski, an associate professor at Iowa State University. For one, humans live longer than many animals. There are some exceptions -- parrots, seabirds, clams and tortoises can all outlive us -- but humans stand out as the longest-lived primates.

"Humans live for many more years past our reproductive prime," Bronikowski said. "If we were like other mammals, we would start dying fairly rapidly after we reach mid-life. But we don't," she said.

"There's been this argument in the scientific literature for a long time that human aging was unique, but we didn't have data on aging in wild primates besides chimps until recently," said co-author Susan Alberts, associate director at the NSF-funded National Evolutionary Synthesis Center in Durham, N.C., and a biologist at Duke University.

The researchers combined data from long-term studies of seven species of wild primates: capuchin monkeys from Costa Rica, muriqui monkeys from Brazil, baboons and blue monkeys from Kenya, chimpanzees from Tanzania, gorillas from Rwanda, and sifaka lemurs from Madagascar.

The team focused not on the inevitable decline in health or fertility that come with advancing age, but rather on the risk of dying. When they compared human aging rates -- measured as the rate at which mortality risk increases with age -- to similar data for nearly 3,000 individual monkeys, apes and lemurs, the human data fell neatly within the primate continuum.

"Human patterns are not strikingly different, even though wild primates experience sources of mortality from which humans may be protected," the authors wrote in a letter to Science.

The results also confirm a pattern observed in humans and elsewhere in the animal kingdom: as males age, they die sooner than their female counterparts. In primates, the mortality gap between males and females is narrowest for the species with the least amount of male-male aggression -- a monkey called the muriqui -- the researchers report.

"Muriquis are the only species in our sample in which males do not compete overtly with one another for access to mates," said co-author Karen Strier, an anthropologist at the University of Wisconsin who has studied muriquis since 1982. The results suggest the reason why males of other species die faster than females may be the stress and strain of competition, the authors said.

Do the findings have any practical implications for humans? Modern medicine is helping humans live longer than ever before, the researchers note.

"Yet we still don't know what governs maximum life span," Alberts said. "Some human studies suggest we might be able to live a lot longer than we do now. Looking to other primates to understand where we are and aren't flexible in our aging will help answer that question."

Synthetic Compound May Lead to Drugs to Fight Pancreatic, Lung Cancer

ScienceDaily (Mar. 10, 2011) — Researchers at UT Southwestern Medical Center have identified a chemical compound that may eventually lead to a drug that fights cancers that are dependent on a particular anti-viral enzyme for growth.

The researchers are testing the compound's effectiveness at fighting tumors in mice. If it is successful, they will then work to develop a drug based on the compound to combat pancreatic and non-small cell lung cancer, two cancer types in which this particular enzyme, TBK-1, often is required for cancer cell survival.

"Our prediction is that TBK-1 is a good pharmacological intervention target for a subset of lung and pancreas cancers that are addicted to the activity of this enzyme. We believe there is a large population of cancer patients that could respond to inhibition of this activity," said Dr. Michael White, professor of cell biology and senior author of the study in the Feb. 18 issue of Molecular Cell.

The investigation, which lasted three and a half years, revealed how activation of the natural virus-fighting protein TBK-1 is hijacked in cancer cells to support growth and survival.

More than 250,000 compounds were screened to find one that would inhibit the enzyme's cancer-protection mechanism. The most effective, a compound called 6-aminopyrazolopyrimidine developed in collaboration with pharmaceutical company Amgen, blocked TBK-1's effects in 40 percent to 50 percent of the non-small cell lung cancer and pancreatic cancer tissue cultures tested, reducing cancer growth. TBK-1 is activated by the Ras family of oncogenes, which are mutated in 40 percent of lung cancers and 90 percent of pancreatic cancers.

"We found a biological activity that some cancer cells need to be able to survive, and we found a way to turn it off," said Dr. White.

The next step, he said, would be ascertaining in rodents whether 6-aminopyrazolopyrimidine can permeate tumors, "hit the target and be effective." If the compound continues to demonstrate efficacy, researchers would begin work to develop a drug with the compound's properties for further testing.

The compound appears to migrate into all tissues of studied mice, but the UT Southwestern researchers don't know yet if it will penetrate solid tumors in the animal, "which is an incredibly important step in evaluating chemicals as drug leads," Dr. White said.

"We've illuminated the dark matter of regulation of an incredibly important oncogenic survival pathway. We've found a new regulatory arm of this pathway, and we've discovered you can inhibit it pharmacologically. That's target validation. The next step is to translate that target validation into development of a medicine," he said.

Other UT Southwestern researchers involved in the study were lead author Yi-Hung Ou, graduate student in cancer biology; Michael Torres and Rosalyn Ram, student research assistants in cancer biology; Dr. Tzuling Cheng, postdoctoral researcher in pediatrics; Dr. Christina Roland, surgery resident; and Dr. Rolf Brekken, associate professor of surgery and pharmacology. Researchers from Hybrigenics of Paris and Amgen Inc. of Thousand Oaks, Calif., also participated.

The work was supported by the National Institutes of Health and the Welch Foundation.