Colorado State University researchers have discovered that mosquitoes that transmit deadly viruses such as dengue avoid becoming ill by mounting an
immediate, potent immune response. Because their immune system does not eliminate the virus, however, they are able to pass it on to a new victim. In
a study published February 13 in the open-access journal PLoS Pathogens, the researchers show that RNA interference - the mosquito immune response
-- is initiated immediately after they ingest blood containing dengue virus, but the virus multiplies in the mosquitoes nevertheless.
Dengue fever and dengue hemorrhagic fever are major global public health burdens, with up to 100 million cases occurring annually, yet no vaccines or
specific preventative medicines are currently available. The Aedes aegypti mosquito transmits dengue virus. Determining how the virus evades the
mosquito's defense is an important next step in research that aims to fight disease by interrupting the growth of dengue virus within the mosquito
before it can be transmitted.
RNA interference is an evolutionarily ancient antiviral defense used by mosquitoes and other invertebrates to destroy the RNA of many invading
arthropod-borne viruses. This team of researchers previously showed that ramping up the RNA interference response in mosquitoes prevented dengue
infection, and now they show that temporarily impairing this immune response increased virus transmission.
The investigators analyzed RNA from adult mosquitoes, finding that both the trigger and initiator molecules for RNA interference were formed after
infection, yet viral RNA could readily be detected in the same mosquitoes. They also measured infectious virus rates in the mosquitoes' saliva,
which revealed levels whereby the mosquitoes could transmit the disease to humans.
These findings indicate that genetic manipulation of RNA interference could be a significant weapon in stopping dengue virus transmission by Aedes
aegypti.
CITATION:
"Dengue Virus Type 2 Infections of Aedes aegypti
Are Modulated by the Mosquito's RNA Interference Pathway."
PLoS Pathog 5(2): e1000299. doi:10.1371/journal.ppat.1000299
dx.plos/10.1371/journal.ppat.1000299
About PLoS Pathogens
PLoS Pathogens publishes outstanding original articles that significantly advance the understanding of pathogens and how they
interact with their host organisms. All works published in PLoS Pathogens are open access. Everything is immediately available subject only to the
condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses
the Creative Commons Attribution License.
plospathogens
About the Public Library of Science
The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical
literature a freely available public resource.
Public Library of Science
пятница, 19 августа 2011 г.
вторник, 16 августа 2011 г.
Brain Research Poised To Dramatically Advance Global Society
World-renowned scientists convened at George Mason University on May 21 and 22 to call for a 10-year intellectual revolution - the "decade of the mind." The proceedings that will be published after this historic gathering will make the case for a $4 billion public research initiative dedicated to reaching the next level of understanding the human brain--the yet-to-be-discovered inner workings of the mind. The symposium also outlined the dramatic implications the decade will have on the global economy and health care.
"We are at the 'tipping point' of making enormous advances in public health, particularly in managing diseases that affect the mind, such as Alzheimer's disease, Parkinson's disease, autism and schizophrenia," said Jim Olds, director of Mason's Krasnow Institute for Advanced Study. "We at Mason are honored to be hosting this gathering of the world's leading researchers in brain study who together will outline the vision for the 'Decade of the Mind' that we will present to federal policymakers."
The two-day symposium included nine sessions, each featuring one aspect of brain research, and was moderated by scientists from the Krasnow Institute for Advanced Study. The symposium was anchored by a plenary session including the nine panelists. Moderated by New York Times science writer George Johnson, the session provided an open forum for the scientists to discuss their groundbreaking research in areas such as neuroscience, neurobiology, computer science, psychology, robotics and economics. The panel also explained the urgency to continue the study of the human mind and the benefits this research could bring to society.
"It is our intention to cover a lot of ground in two days because we need to capture the magnitude of the impact of what we are proposing to Congress," said Olds. "A 10-year focus to bring the enormous promise of brain research will launch an intellectual revolution here and throughout the world, with lasting impacts on society."
In the United States today, more than five million people are living with Alzheimer's disease according to the Alzheimer's Association. The number of people affected by this ultimately fatal disease will only increase over the next decade as early onset Alzheimer's begins to affect the baby boomer generation.
Today, one in 17 Americans suffer from a serious mental illness, the leading cause of disability in the U.S. for people 15 to 44 years old, according to the National Institute on Mental Health. New brain research during the initiative, coupled with advances in MRI technology and other non-invasive research tools, will allow scientists to better understand what causes these illnesses and how to manage or cure them.
This initiative also could help thousands of soldiers, sailors and airmen who have served in Afghanistan and Iraq more quickly and easily recover from brain injuries caused during combat, especially by improvised explosive devices.
Further research could allow advances in robotics and artificial intelligence that would make most future military vehicles - and aircraft - operate unmanned and autonomously, thereby saving thousands of lives during combat operations.
"The economic impact of the 'Decade of the Mind' will be felt in all levels of society," said Olds. "By translating our knowledge of the human mind to building more intelligent machines and computer applications, we can improve the welfare of millions of people worldwide."
The groundwork for this initiative was laid during the "Decade of the Brain," declared by President George H.W. Bush in 1990. It produced immense advances in brain research, including the development of MRI scanners and progress in the understanding of Alzheimer's disease and mental illness. Using these advances as a basis for further exploration into the human mind, this new decade would provide the nation's scientific community the opportunity to understand more about the mind than ever before and tackle some of society's most pressing challenges.
Decade of the Mind symposium presenters included: Marcus Raichle, MD, Washington University (St. Louis) School of Medicine; Nancy Kanwisher, PhD, Massachusetts Institute of Technology; John Holland, PhD, University of Michigan; Dharmendra Modha, PhD, IBM; Giulio Tononi, MD, PhD, University of Wisconsin; George A. Bekey, PhD, University of Southern California; Gordon Shepherd, PhD, Yale University; Vernon Smith, PhD, George Mason University, Nobel Laureate; and George Johnson, New York Times science writer, plenary session moderator.
For more information about the Decade of the Mind symposium, visit krasnow.gmu/decade.
About the Krasnow Institute for Advanced Study
The Krasnow Institute for Advanced Study seeks to expand understanding of mind, brain and intelligence by conducting research at the intersection of the separate fields of cognitive psychology, neurobiology and the computer-driven study of artificial intelligence and complex adaptive systems. These separate disciplines increasingly overlap and promise progressively deeper insight into human thought processes. The institute also examines how new insights from cognitive science research can be applied for human benefit in the areas of mental health, neurological disease, education and computer design.
About George Mason University
George Mason University, located in the heart of Northern Virginia's technology corridor near Washington, D.C., is an innovative, entrepreneurial institution with national distinction in a range of academic fields. With strong undergraduate and graduate degree programs in engineering, information technology, biotechnology and health care, Mason prepares its alumni to succeed in the workforce and meet the needs of the region and the world. Mason professors conduct groundbreaking research in areas such as cancer, climate change, information technology and the biosciences, and Mason's Center for the Arts brings world-renowned artists, musicians and actors to its stage. Its School of Law is recognized by U.S. News and World Report as one of the top 50 law schools in the United States.
Contact: Jim Greif
George Mason University
"We are at the 'tipping point' of making enormous advances in public health, particularly in managing diseases that affect the mind, such as Alzheimer's disease, Parkinson's disease, autism and schizophrenia," said Jim Olds, director of Mason's Krasnow Institute for Advanced Study. "We at Mason are honored to be hosting this gathering of the world's leading researchers in brain study who together will outline the vision for the 'Decade of the Mind' that we will present to federal policymakers."
The two-day symposium included nine sessions, each featuring one aspect of brain research, and was moderated by scientists from the Krasnow Institute for Advanced Study. The symposium was anchored by a plenary session including the nine panelists. Moderated by New York Times science writer George Johnson, the session provided an open forum for the scientists to discuss their groundbreaking research in areas such as neuroscience, neurobiology, computer science, psychology, robotics and economics. The panel also explained the urgency to continue the study of the human mind and the benefits this research could bring to society.
"It is our intention to cover a lot of ground in two days because we need to capture the magnitude of the impact of what we are proposing to Congress," said Olds. "A 10-year focus to bring the enormous promise of brain research will launch an intellectual revolution here and throughout the world, with lasting impacts on society."
In the United States today, more than five million people are living with Alzheimer's disease according to the Alzheimer's Association. The number of people affected by this ultimately fatal disease will only increase over the next decade as early onset Alzheimer's begins to affect the baby boomer generation.
Today, one in 17 Americans suffer from a serious mental illness, the leading cause of disability in the U.S. for people 15 to 44 years old, according to the National Institute on Mental Health. New brain research during the initiative, coupled with advances in MRI technology and other non-invasive research tools, will allow scientists to better understand what causes these illnesses and how to manage or cure them.
This initiative also could help thousands of soldiers, sailors and airmen who have served in Afghanistan and Iraq more quickly and easily recover from brain injuries caused during combat, especially by improvised explosive devices.
Further research could allow advances in robotics and artificial intelligence that would make most future military vehicles - and aircraft - operate unmanned and autonomously, thereby saving thousands of lives during combat operations.
"The economic impact of the 'Decade of the Mind' will be felt in all levels of society," said Olds. "By translating our knowledge of the human mind to building more intelligent machines and computer applications, we can improve the welfare of millions of people worldwide."
The groundwork for this initiative was laid during the "Decade of the Brain," declared by President George H.W. Bush in 1990. It produced immense advances in brain research, including the development of MRI scanners and progress in the understanding of Alzheimer's disease and mental illness. Using these advances as a basis for further exploration into the human mind, this new decade would provide the nation's scientific community the opportunity to understand more about the mind than ever before and tackle some of society's most pressing challenges.
Decade of the Mind symposium presenters included: Marcus Raichle, MD, Washington University (St. Louis) School of Medicine; Nancy Kanwisher, PhD, Massachusetts Institute of Technology; John Holland, PhD, University of Michigan; Dharmendra Modha, PhD, IBM; Giulio Tononi, MD, PhD, University of Wisconsin; George A. Bekey, PhD, University of Southern California; Gordon Shepherd, PhD, Yale University; Vernon Smith, PhD, George Mason University, Nobel Laureate; and George Johnson, New York Times science writer, plenary session moderator.
For more information about the Decade of the Mind symposium, visit krasnow.gmu/decade.
About the Krasnow Institute for Advanced Study
The Krasnow Institute for Advanced Study seeks to expand understanding of mind, brain and intelligence by conducting research at the intersection of the separate fields of cognitive psychology, neurobiology and the computer-driven study of artificial intelligence and complex adaptive systems. These separate disciplines increasingly overlap and promise progressively deeper insight into human thought processes. The institute also examines how new insights from cognitive science research can be applied for human benefit in the areas of mental health, neurological disease, education and computer design.
About George Mason University
George Mason University, located in the heart of Northern Virginia's technology corridor near Washington, D.C., is an innovative, entrepreneurial institution with national distinction in a range of academic fields. With strong undergraduate and graduate degree programs in engineering, information technology, biotechnology and health care, Mason prepares its alumni to succeed in the workforce and meet the needs of the region and the world. Mason professors conduct groundbreaking research in areas such as cancer, climate change, information technology and the biosciences, and Mason's Center for the Arts brings world-renowned artists, musicians and actors to its stage. Its School of Law is recognized by U.S. News and World Report as one of the top 50 law schools in the United States.
Contact: Jim Greif
George Mason University
суббота, 13 августа 2011 г.
Autophagy Is The Key To Survival And Virulence For A Fungal Pathogen
Autophagy is a process whereby cells recycle material during stress situations, such as when nutrients are scarce. Some cells also use this process as an immune defense mechanism to eliminate pathogens. However, new data, generated in mice by Peter Williamson and colleagues, at the University of Illinois at Chicago, has identified autophagy as a new virulence-associated trait and survival mechanism for Cryptococcus neoformans - a fungal pathogen that commonly infects immunocompromised individuals, such as those with HIV.
In the study, a mutant form of C. neoformans that lacked the protein Vps34 PI3K (known as the vps34D mutant) was found to be less able to form autophagy-related 8-labeled (Atg8-labeled) vesicles than normal C. neoformans. Furthermore, the vps34D mutant was less virulent in mice than normal C. neoformans. Consistent with a crucial role for autophagy in determining the extent of the disease caused by infection with C. neoformans, a strain of C. neoformans in which Atg8 expression was knocked down showed reduced virulence in mice. The authors therefore suggested that more detailed understanding of this virulence pathway might lead to new drugs for treating individuals who become infected with C. neoformans.
TITLE: PI3K signaling of autophagy is required for starvation tolerance and virulence of Cryptococcal neoformans
AUTHOR CONTACT:
Peter R. Williamson
University of Illinois at Chicago, Chicago, Illinois, USA.
Source: Karen Honey
Journal of Clinical Investigation
In the study, a mutant form of C. neoformans that lacked the protein Vps34 PI3K (known as the vps34D mutant) was found to be less able to form autophagy-related 8-labeled (Atg8-labeled) vesicles than normal C. neoformans. Furthermore, the vps34D mutant was less virulent in mice than normal C. neoformans. Consistent with a crucial role for autophagy in determining the extent of the disease caused by infection with C. neoformans, a strain of C. neoformans in which Atg8 expression was knocked down showed reduced virulence in mice. The authors therefore suggested that more detailed understanding of this virulence pathway might lead to new drugs for treating individuals who become infected with C. neoformans.
TITLE: PI3K signaling of autophagy is required for starvation tolerance and virulence of Cryptococcal neoformans
AUTHOR CONTACT:
Peter R. Williamson
University of Illinois at Chicago, Chicago, Illinois, USA.
Source: Karen Honey
Journal of Clinical Investigation
среда, 10 августа 2011 г.
Discovery Explains How Cold Sore Virus Hides During Inactive Phase
Now that Duke University Medical Center scientists have figured out how the virus that causes cold sores hides out, they may have a way to wake it up and kill it.
Cold sores, painful, unsightly blemishes around the mouth, have so far evaded a cure or even prevention. They're known to be caused by the herpes simplex virus 1 (HSV1), which lies dormant in the trigeminal nerve of the face until triggered to reawaken by excessive sunlight, fever, or other stresses.
"We have provided a molecular understanding of how HSV1 hides and then switches back and forth between the latent (hidden) and active phases," said Bryan Cullen, Duke professor of molecular genetics and microbiology.
His group's findings, published in Nature, also provide a framework for studying other latent viruses, such as the chicken pox virus, which can return later in life as a case of shingles, and herpes simplex 2 virus, a genitally transmitted virus that also causes painful sores, Cullen said.
Most of the time, HSV1 lives quietly for years, out of reach of any therapy we have against it. It does not replicate itself during this time and only produces one molecular product, called latency associated transcript RNA or LAT RNA.
"It has always been a mystery what this product, LAT RNA, does," Cullen said. "Usually viral RNAs exist to make proteins that are of use to the virus, but this LAT RNA is extremely unstable and does not make any proteins."
In studies of mice, the team showed that the LAT RNA is processed into smaller strands, called microRNAs, that block production of the proteins that make the virus turn on active replication. As long as the supply of microRNAs is sufficient, the virus stays dormant.
After a larger stress, however, the virus starts making more messenger RNA than the supply of microRNAs can block, and protein manufacturing begins again. This tips the balance, and the virus ultimately makes proteins that begin active viral replication.
The new supply of viruses then travels back down the trigeminal nerve, to the site of the initial infection at the mouth. A cold sore always erupts in the same place and is the source of viruses that might infect another person, either from direct contact, or sharing eating utensils or towels, Cullen said.
The approach to curing this nuisance would be a combination therapy, Cullen said. "Inactive virus is completely untouchable by any treatment we have. Unless you activate the virus, you can't kill it," he said.
Cullen and his team are testing a new drug designed to very precisely bind to the microRNAs that keep the virus dormant. If it works, the virus would become activated and start replicating.
Once the virus is active, a patient would then take acyclovir, a drug that effectively kills replicating HSV1.
"In principle, you could activate and then kill all of the virus in a patient," Cullen said. "This would completely cure a person, and you would never get another cold sore."
He and the team are working with drug development companies in animal trials to begin to answer questions about how to deliver this drug most effectively.
Co-authors included Jennifer Lin Umbach, Ph.D., and Heather W. Karnowski, B.S., of the Duke Department of Molecular Genetics and Microbiology and Center for Virology, and Martha F. Kramer, Igor Jurak, and Prof. Donald M. Coen of the Department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School. This work was supported by two NIH grants.
Source: Mary Jane Gore
Duke University Medical Center
View drug information on Acyclovir Capsules.
Cold sores, painful, unsightly blemishes around the mouth, have so far evaded a cure or even prevention. They're known to be caused by the herpes simplex virus 1 (HSV1), which lies dormant in the trigeminal nerve of the face until triggered to reawaken by excessive sunlight, fever, or other stresses.
"We have provided a molecular understanding of how HSV1 hides and then switches back and forth between the latent (hidden) and active phases," said Bryan Cullen, Duke professor of molecular genetics and microbiology.
His group's findings, published in Nature, also provide a framework for studying other latent viruses, such as the chicken pox virus, which can return later in life as a case of shingles, and herpes simplex 2 virus, a genitally transmitted virus that also causes painful sores, Cullen said.
Most of the time, HSV1 lives quietly for years, out of reach of any therapy we have against it. It does not replicate itself during this time and only produces one molecular product, called latency associated transcript RNA or LAT RNA.
"It has always been a mystery what this product, LAT RNA, does," Cullen said. "Usually viral RNAs exist to make proteins that are of use to the virus, but this LAT RNA is extremely unstable and does not make any proteins."
In studies of mice, the team showed that the LAT RNA is processed into smaller strands, called microRNAs, that block production of the proteins that make the virus turn on active replication. As long as the supply of microRNAs is sufficient, the virus stays dormant.
After a larger stress, however, the virus starts making more messenger RNA than the supply of microRNAs can block, and protein manufacturing begins again. This tips the balance, and the virus ultimately makes proteins that begin active viral replication.
The new supply of viruses then travels back down the trigeminal nerve, to the site of the initial infection at the mouth. A cold sore always erupts in the same place and is the source of viruses that might infect another person, either from direct contact, or sharing eating utensils or towels, Cullen said.
The approach to curing this nuisance would be a combination therapy, Cullen said. "Inactive virus is completely untouchable by any treatment we have. Unless you activate the virus, you can't kill it," he said.
Cullen and his team are testing a new drug designed to very precisely bind to the microRNAs that keep the virus dormant. If it works, the virus would become activated and start replicating.
Once the virus is active, a patient would then take acyclovir, a drug that effectively kills replicating HSV1.
"In principle, you could activate and then kill all of the virus in a patient," Cullen said. "This would completely cure a person, and you would never get another cold sore."
He and the team are working with drug development companies in animal trials to begin to answer questions about how to deliver this drug most effectively.
Co-authors included Jennifer Lin Umbach, Ph.D., and Heather W. Karnowski, B.S., of the Duke Department of Molecular Genetics and Microbiology and Center for Virology, and Martha F. Kramer, Igor Jurak, and Prof. Donald M. Coen of the Department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School. This work was supported by two NIH grants.
Source: Mary Jane Gore
Duke University Medical Center
View drug information on Acyclovir Capsules.
воскресенье, 7 августа 2011 г.
'LEGO-Like' Building Blocks To Halt Cell Growth Wins Hebrew University Prize
A method for delivery of drugs to targeted cells through the design of specific molecular structures called SIB (Small Integrated Building Blocks) has won a prestigious scientific prize for a Ph.D. student in organic chemistry at the Hebrew University of Jerusalem
Jerusalemite Nir Qvit, 34, will be one of those receiving the Kaye Innovation Award on June 13, during the 69th meeting of the Hebrew university Board of Governors.
Qvit has shown through his research that it is possible to greatly increase drug delivery efficiency by designing specific molecular structures made up of known pharmaceutically effective peptides (small protein molecules) that are attached to tailor-made, geometric-like structures called "scaffolding."
Each scaffold is specifically designed to combine the peptides in such a way that they will form an effective medicinal combination and so that they will bind to the receptors of specific targeted cells. Qvit refers to his process as somewhat analogous to building different kinds of structures through the use of LEGO.
Qvit, a student of Prof. Chaim Gilon of the Department of Organic Chemistry, has shown, for example, that with a particular combination of peptides and scaffold design, it is possible to create a synthetic molecule that will bind to the IGF-1 (insulin-like growth factor-1) receptor. IGF-1 is a protein that plays a critical role in the proliferation of many cancers, including prostate, lung, breast, colon and brain cancers. The binding action of the molecule to the receptor inhibits the activation of the IGF-1 protein in the cells, thus halting the cancerous growth.
Through this process of "combinational chemistry," involving peptides and scaffold design, Qvit says that many different types of molecules can be built that will reach specifically targeted cells, offering hope for treatment of not only cancer, but other diseases as well, without harming healthy cells.
The Kaye Innovation Awards have been given annually since 1994. Isaac Kaye of England, a prominent industrialist in the pharmaceutical industry, established the awards to encourage faculty, staff, and students of the Hebrew University to develop innovative methods and inventions with good commercial potential which will benefit the university and society.
Contact: Jerry Barach
The Hebrew University of Jerusalem
Jerusalemite Nir Qvit, 34, will be one of those receiving the Kaye Innovation Award on June 13, during the 69th meeting of the Hebrew university Board of Governors.
Qvit has shown through his research that it is possible to greatly increase drug delivery efficiency by designing specific molecular structures made up of known pharmaceutically effective peptides (small protein molecules) that are attached to tailor-made, geometric-like structures called "scaffolding."
Each scaffold is specifically designed to combine the peptides in such a way that they will form an effective medicinal combination and so that they will bind to the receptors of specific targeted cells. Qvit refers to his process as somewhat analogous to building different kinds of structures through the use of LEGO.
Qvit, a student of Prof. Chaim Gilon of the Department of Organic Chemistry, has shown, for example, that with a particular combination of peptides and scaffold design, it is possible to create a synthetic molecule that will bind to the IGF-1 (insulin-like growth factor-1) receptor. IGF-1 is a protein that plays a critical role in the proliferation of many cancers, including prostate, lung, breast, colon and brain cancers. The binding action of the molecule to the receptor inhibits the activation of the IGF-1 protein in the cells, thus halting the cancerous growth.
Through this process of "combinational chemistry," involving peptides and scaffold design, Qvit says that many different types of molecules can be built that will reach specifically targeted cells, offering hope for treatment of not only cancer, but other diseases as well, without harming healthy cells.
The Kaye Innovation Awards have been given annually since 1994. Isaac Kaye of England, a prominent industrialist in the pharmaceutical industry, established the awards to encourage faculty, staff, and students of the Hebrew University to develop innovative methods and inventions with good commercial potential which will benefit the university and society.
Contact: Jerry Barach
The Hebrew University of Jerusalem
четверг, 4 августа 2011 г.
Assembly Of Molecules Critical To Protein Function Witnessed By Researchers
A Virginia Tech research group lead by two biochemistry graduate students has isolated proteins responsible for the iron-sulfur cluster assembly process and witnessed the necessary protein interactions in vivo - within a cell. They have captured pathway intermediates and observed protein interactions between the two major players in iron-sulfur cluster assembly.
Iron-sulfur clusters are critical to life on earth. They are necessary for protein function in cellular processes, such as respiration in humans and other organisms and photosynthesis by plants. "But we do not understand how Fe-S molecules are made or the specifics of how they bond," said Callie Raulfs of Christiansburg, Va. "It does not happen spontaneously. It has to be regulated."
Diseases such as Friedrich's ataxia and several types of anemia are a result of iron-sulfur cluster (ISC) assembly malfunctions.
Using genetic and biochemical techniques, Ph.D. students Raulfs and Ina P. O'Carroll, of Tirana, Albania, have isolated components of the ISC machinery in the process of making iron-sulfur clusters. "This work provides insight into the sequential steps of the iron-sulfur cluster assembly process, helping to explain how molecules of iron and sulfur are synthesized and distributed in cells," said O'Carroll.
The work, "In vivo iron-sulfur cluster formation," by Raulfs, O'Carroll, Virginia Tech post-doctoral associates Patricia C. Dos Santos of Brazil and Mihaela-Carmen Unciuleac of Romania, and Dennis R. Dean of Blacksburg, professor of biochemistry and director of the Fralin Biotechnology Center at Virginia Tech, has been published in the Proceedings of the National Academy of Science (PNAS) Online Early Edition the week of June 16-20, 2008.
Previous studies by Dean and others have demonstrated that proteins can assemble clusters from components in vitro systems - that is, outside of an organism. Ten years ago, working with nitrogen-fixation systems, Dean's lab was the first to discover ISC proteins. Now Dean's students, Raulfs and O'Carroll, are the first to witness the assembly process in vivo - within a cell.
"The cool thing is we've come up with a way to observe ISC proteins from their native host with a cluster attached," said O'Carroll. "The system also allows us to capture different phases of the process."
The students have isolated three different intermediates of the ISC proteins involved in intercellular biosynthesis - or the cluster assembly process.
Rather than multiplying the proteins by placing them in E. coli, the Virginia Tech team used Azotobacter vinelandii, an aerobic, soil microbe that fixes nitrogen from the atmosphere, to obtain natural levels of the ISC proteins. "A vinelandii grows quickly and keeps the interior of the cell free of oxygen, which is important, since oxygen can destroy Fe-S clusters," said Raulfs, who first isolated a protein complex with a cluster attached, providing in vivo evidence that the two proteins get together and form a cluster.
"Because we are isolating proteins from the cell, we are also able to observe interactions between different Fe-S cluster asembly proteins," said O'Carroll. "We have been able to isolate a complex between the two major players in iron-sulfur assembly, the cluster assembly scaffold (IscU) and the sulfur-delivery protein (IscS)."
The methodology is to add a histidine amino acid tag to the ISC proteins "so we can fish the proteins out of the cell," said O'Carroll.
"Because we are fishing the cluster-containing protein out of the cell that has all of the other assembly proteins present at physiological levels, we are able to observe what else comes with the protein. What was really exciting in this case was that we saw large amounts of one of the other iron sulfur cluster assembly protein, IscS." said O'Carroll.
The work marks the first time researchers have been able to observe ISC proteins from the balanced environment of the native cell.
Next, they plan to determine the role of the individual genes in the set that produces ISC proteins in order to determine the effect of each gene on the assembly process. "The goal is to determine the events and the order in the ISC assembly process so we can figure out how cells make clusters and deliver them to specific target proteins," said O'Carroll.
The researchers are now developing a system that others can use to study proteins.
Raulfs received her undergraduate degree from the College of William and Mary. She has been a fellow in the Exploring Interfaces through Graduate Education and Research (EIGER) project, a National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) program at Virginia Tech.
O'Carroll received her undergraduate degree from McDaniel College. Dos Santos is the senior postdoc in the Dean lab. Unciuleac is now a post-doctoral fellow with the Molecular Biology Program at the Sloan-Kettering Institute.
The research is supported by the National Science Foundation.
Source: Susan Trulove
Virginia Tech
Iron-sulfur clusters are critical to life on earth. They are necessary for protein function in cellular processes, such as respiration in humans and other organisms and photosynthesis by plants. "But we do not understand how Fe-S molecules are made or the specifics of how they bond," said Callie Raulfs of Christiansburg, Va. "It does not happen spontaneously. It has to be regulated."
Diseases such as Friedrich's ataxia and several types of anemia are a result of iron-sulfur cluster (ISC) assembly malfunctions.
Using genetic and biochemical techniques, Ph.D. students Raulfs and Ina P. O'Carroll, of Tirana, Albania, have isolated components of the ISC machinery in the process of making iron-sulfur clusters. "This work provides insight into the sequential steps of the iron-sulfur cluster assembly process, helping to explain how molecules of iron and sulfur are synthesized and distributed in cells," said O'Carroll.
The work, "In vivo iron-sulfur cluster formation," by Raulfs, O'Carroll, Virginia Tech post-doctoral associates Patricia C. Dos Santos of Brazil and Mihaela-Carmen Unciuleac of Romania, and Dennis R. Dean of Blacksburg, professor of biochemistry and director of the Fralin Biotechnology Center at Virginia Tech, has been published in the Proceedings of the National Academy of Science (PNAS) Online Early Edition the week of June 16-20, 2008.
Previous studies by Dean and others have demonstrated that proteins can assemble clusters from components in vitro systems - that is, outside of an organism. Ten years ago, working with nitrogen-fixation systems, Dean's lab was the first to discover ISC proteins. Now Dean's students, Raulfs and O'Carroll, are the first to witness the assembly process in vivo - within a cell.
"The cool thing is we've come up with a way to observe ISC proteins from their native host with a cluster attached," said O'Carroll. "The system also allows us to capture different phases of the process."
The students have isolated three different intermediates of the ISC proteins involved in intercellular biosynthesis - or the cluster assembly process.
Rather than multiplying the proteins by placing them in E. coli, the Virginia Tech team used Azotobacter vinelandii, an aerobic, soil microbe that fixes nitrogen from the atmosphere, to obtain natural levels of the ISC proteins. "A vinelandii grows quickly and keeps the interior of the cell free of oxygen, which is important, since oxygen can destroy Fe-S clusters," said Raulfs, who first isolated a protein complex with a cluster attached, providing in vivo evidence that the two proteins get together and form a cluster.
"Because we are isolating proteins from the cell, we are also able to observe interactions between different Fe-S cluster asembly proteins," said O'Carroll. "We have been able to isolate a complex between the two major players in iron-sulfur assembly, the cluster assembly scaffold (IscU) and the sulfur-delivery protein (IscS)."
The methodology is to add a histidine amino acid tag to the ISC proteins "so we can fish the proteins out of the cell," said O'Carroll.
"Because we are fishing the cluster-containing protein out of the cell that has all of the other assembly proteins present at physiological levels, we are able to observe what else comes with the protein. What was really exciting in this case was that we saw large amounts of one of the other iron sulfur cluster assembly protein, IscS." said O'Carroll.
The work marks the first time researchers have been able to observe ISC proteins from the balanced environment of the native cell.
Next, they plan to determine the role of the individual genes in the set that produces ISC proteins in order to determine the effect of each gene on the assembly process. "The goal is to determine the events and the order in the ISC assembly process so we can figure out how cells make clusters and deliver them to specific target proteins," said O'Carroll.
The researchers are now developing a system that others can use to study proteins.
Raulfs received her undergraduate degree from the College of William and Mary. She has been a fellow in the Exploring Interfaces through Graduate Education and Research (EIGER) project, a National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) program at Virginia Tech.
O'Carroll received her undergraduate degree from McDaniel College. Dos Santos is the senior postdoc in the Dean lab. Unciuleac is now a post-doctoral fellow with the Molecular Biology Program at the Sloan-Kettering Institute.
The research is supported by the National Science Foundation.
Source: Susan Trulove
Virginia Tech
понедельник, 1 августа 2011 г.
Evolution's Steps Revealed By Structure Of 450 Million Year Old Protein
A detailed map that pinpoints the location of every atom in a 450-million-yeard-old resurrected protein reveals the precise evolutionary steps needed to create the molecule's modern version, according to researchers from the University of North Carolina at Chapel Hill and the University of Oregon.
Until now, scientists trying to unravel the evolution of the proteins and other molecules necessary for life have worked backwards, making educated guesses based on modern human body chemistry. By moving forward from an ancient protein, the team laid out the step-by-step progression required to reach its current form and function.
The study appears in the journal Science.
"We were able to see exactly how mutations in the ancient structure led to the modern receptor," said lead author Eric Ortlund, who carried out the research as a UNC-Chapel Hill postdoctoral fellow. Ortlund is now an assistant professor of biochemistry in the Emory University School of Medicine.
In the current study, Ortlund and Matt Redinbo, a professor of chemistry, biochemistry and biophysics at UNC-Chapel Hill, generated a three-dimensional picture of the ancient receptor with an imaging technique called X-ray crystallography. The nanoscale image revealed the receptor's structure, down to the placement of every atom. With the structure in place, Ortlund and his colleagues retraced evolution's path.
The researchers examined the precursor to a modern protein known as a glucocorticoid receptor. In humans, the receptor plays a crucial role, responding to the hormone cortisol and regulating the body's stress response. The two -- receptor and hormone -- fit together as precisely as a lock and key. The precursor preferred a different hormone, so several mutations were necessary before the lock could fit the cortisol key.
The University of Oregon team, which included postdoctoral scientist Jamie Bridgham, resurrected the ancient protein via a large database of modern receptor genes. This earlier work, which compared the genetic similarities and differences among two of these modern genes, found the receptor descended from a single common genetic ancestor 450 million years ago. The researchers then recreated the ancient receptor in the laboratory.
Only seven mutations were needed to bridge the 450-million-year gulf, the researchers found. However, not every mutation changed the protein's function. These "permissive" mutations appear to pave the way for future, more significant changes. "It's like they prepared for opportunity to knock in the form of a new hormone," Ortlund said.
The permissive mutations bolstered the receptor's structure, like contractors reinforce a historic home's foundation before making renovations. After these changes took place, a more extreme mutation repositioned an entire group of atoms, bringing them closer to fitting the cortisol hormone. Another created the tight new fit with cortisol.
"These permissive mutations are chance events. If they hadn't happened first, then the path to the new function could have become an evolutionary road not taken," said co-author Joe Thornton, a professor of evolutionary biology at the University of Oregon.
The researchers worked out which mutations came first by synthesizing different versions of the mutated protein in the laboratory. Had the radical mutations come first, the receptor protein would have lost its function entirely, they found.
The research was funded by the National Institutes of Health, the National Science Foundation, a UNC Lineberger Comprehensive Cancer Center fellowship to Ortlund and an Alfred P. Sloan research fellowship to Thornton.
Source: Becky Oskin
University of North Carolina at Chapel Hill
Until now, scientists trying to unravel the evolution of the proteins and other molecules necessary for life have worked backwards, making educated guesses based on modern human body chemistry. By moving forward from an ancient protein, the team laid out the step-by-step progression required to reach its current form and function.
The study appears in the journal Science.
"We were able to see exactly how mutations in the ancient structure led to the modern receptor," said lead author Eric Ortlund, who carried out the research as a UNC-Chapel Hill postdoctoral fellow. Ortlund is now an assistant professor of biochemistry in the Emory University School of Medicine.
In the current study, Ortlund and Matt Redinbo, a professor of chemistry, biochemistry and biophysics at UNC-Chapel Hill, generated a three-dimensional picture of the ancient receptor with an imaging technique called X-ray crystallography. The nanoscale image revealed the receptor's structure, down to the placement of every atom. With the structure in place, Ortlund and his colleagues retraced evolution's path.
The researchers examined the precursor to a modern protein known as a glucocorticoid receptor. In humans, the receptor plays a crucial role, responding to the hormone cortisol and regulating the body's stress response. The two -- receptor and hormone -- fit together as precisely as a lock and key. The precursor preferred a different hormone, so several mutations were necessary before the lock could fit the cortisol key.
The University of Oregon team, which included postdoctoral scientist Jamie Bridgham, resurrected the ancient protein via a large database of modern receptor genes. This earlier work, which compared the genetic similarities and differences among two of these modern genes, found the receptor descended from a single common genetic ancestor 450 million years ago. The researchers then recreated the ancient receptor in the laboratory.
Only seven mutations were needed to bridge the 450-million-year gulf, the researchers found. However, not every mutation changed the protein's function. These "permissive" mutations appear to pave the way for future, more significant changes. "It's like they prepared for opportunity to knock in the form of a new hormone," Ortlund said.
The permissive mutations bolstered the receptor's structure, like contractors reinforce a historic home's foundation before making renovations. After these changes took place, a more extreme mutation repositioned an entire group of atoms, bringing them closer to fitting the cortisol hormone. Another created the tight new fit with cortisol.
"These permissive mutations are chance events. If they hadn't happened first, then the path to the new function could have become an evolutionary road not taken," said co-author Joe Thornton, a professor of evolutionary biology at the University of Oregon.
The researchers worked out which mutations came first by synthesizing different versions of the mutated protein in the laboratory. Had the radical mutations come first, the receptor protein would have lost its function entirely, they found.
The research was funded by the National Institutes of Health, the National Science Foundation, a UNC Lineberger Comprehensive Cancer Center fellowship to Ortlund and an Alfred P. Sloan research fellowship to Thornton.
Source: Becky Oskin
University of North Carolina at Chapel Hill
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