A once-a-month electronic newsletter for basic, preclinical and translational
research news related to the Johns Hopkins School of Medicine. Please forward
freely. Browse back issues of the e-Newsletter in the archive.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
RESEARCH HIGHLIGHTS:
- Researchers Discover Potential New Approach to Treating Diabetes
- First Whole-Genome Scan for Links to Obsessive Compulsive Disorder Reveals Evidence for Genetic Susceptibility
- Shape-Shifting Protein Controls Assembly of Cell Anchor Points
- Identification of a Target of the Gene That Causes Familial Parkinson Disease
- Using –Omics to Identify Potential Her2 Targets
- Taming the Cell’s Quality Control to Effect Cystic Fibrosis Mutation
- A Possible Explanation for Mucolipidosis?
NEWS BRIEFS:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Do you have a manuscript in press? Fax your manuscript or galley proofs to
Media Relations and Public Affairs at 410-614-8951, or e-mail the appropriate
media relations person.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
RESEARCH HIGHLIGHTS:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/2/06
Bone Marrow Cell Migration in Response to Low Oxygen Requires Oxygen Sensor Protein
In a report published in the Journal of Biological Chemistry, Johns Hopkins researchers have shown that the protein called HIF-1 — for hypoxia-inducible factor 1 — is critical for controlling the movement of bone marrow cells, which help grow new blood vessels at sites in the body suffering from low oxygen when atherosclerosis blocks blood vessels.
Movement of a bone marrow cell requires a protein on the surface of the cell called VEGFR1. Manufacture of VEGFR1 increases in low oxygen conditions, yet previously it was not known how VEGFR1 levels are controlled. A research team from Hopkins’ Institute for Cell Engineering, departments of Pediatrics, Medicine, Oncology and Radiation Oncology, and the McKusick-Nathans Institute of Genetic Medicine have shown that VEGFR1 levels are controlled by HIF-1 in bone marrow cells.
HIF-1 turns on specific genes in response to low oxygen and is itself controlled by the amount of available oxygen. HIF-1 reacts with oxygen and becomes chemically altered and degraded. However, when there is little oxygen present, HIF-1 escapes chemical alteration and degradation and is able to turn on genes that help a cell respond to survive low oxygen.
The research team showed that introducing HIF-1 into cultured bone marrow cells causes the cells to make more VEGFR1 and promotes cell migration, even at normal oxygen levels. To test the cells’ response to low oxygen, they grew cells for 24 hours in a dish in either normal air containing 20 percent oxygen or in low oxygen conditions containing 1 percent oxygen. Removing HIF-1 from these cells prevents them from making VEGFR1 and also prevents migration in low oxygen. Moreover, the researchers found that even the low levels of HIF-1 that are present in well-oxygenated cells are essential for VEGFR1 production.
J. Biol. Chem., Vol. 281, Issue 22, 15554-15563, June 2, 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/7/06
Researchers Discover Potential New Approach to Treating Diabetes
Scientists at Johns Hopkins have uncovered a surprising and novel way of lowering blood sugar levels in mice by manipulating the release of sugar by liver cells. The results, published in the June issue of Cell Metabolism, have implications for treating conditions like diabetes.
The research team found that GCN5 chemically alters another protein called PGC-1alpha that normally turns on a set of genes to manufacture enzymes required for glucose release. When GCN5 is fully functional in liver cells, this cascade is turned off and glucose is not released from those cells. Removal of functional GCN5 from liver cells restores the cells’ ability to release glucose.
The researchers showed that GCN5 alters its target, sabotaging it by adding a chemical tag called an acetyl group. By using molecules that glow fluorescently, the researchers saw under high-power microscopes that GCN5 carries its tagged target to a different location in the cell’s nucleus — sequestering it away from the genes it’s normally meant to turn on.
“GCN5 has been generally shown to turn on genes. No one knew that GCN5 could be used to turn off pathways” says Carlos Lerin, Ph.D., lead author of the study and postdoctoral fellow in the department of Cell Biology. “It was a bit of a surprise.”
When the researchers put GCN5 into live mice, they found that it can in fact decrease blood glucose levels. Liver cells in mice that are given no food for 16 hours actively release glucose into the bloodstream. Introducing GCN5 into their livers, however, causes blood glucose levels in these mice to be reduced.
“These results show that changing GCN5 is sufficient to control the sugar balance in mice,” says Pere Puigserver, Ph.D., senior author and assistant professor of Cell Biology. “Therefore, GCN5 has the potential to be a target for therapeutic drug design in the future.”
Read the news release here.
Cell Metabolism, Vol 3, 429-438, June 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/7/06
First Whole-Genome Scan for Links to Obsessive Compulsive Disorder Reveals Evidence for Genetic Susceptibility
A federally funded team of researchers including several from Johns Hopkins have identified six regions of the human genome that might play a role in susceptibility to obsessive compulsive disorder, or OCD. The study was published online June 6 in Molecular Psychiatry.
OCD is characterized by intrusive and senseless thoughts and impulses that together are defined as obsessions, as well as repetitive and intentional behaviors, referred to as compulsions. OCD is estimated to affect up to 3 percent of the American population.
To conduct the study, the researchers collected blood samples from 1,008 individuals from a total of 219 families in which at least two siblings were clinically diagnosed with OCD.
DNA from each sample was analyzed by the Hopkins Center for Inherited Disease Research (CIDR) using both molecular biology and statistical analysis computer programs. Specific DNA sequences — known as genetic markers — on chromosomes 1, 7, 6, and 15 and two markers on chromosome 3 appear more frequently in the patients with OCD than in those without it. The researchers want to further analyze the genetic regions they identified in this report and use more markers to possibly narrow down these regions to identify OCD risk genes.
Careful genetic analysis of different clinical categories of OCD has been limited by currently existing computer programs used in analyzing this type of data. The vast amount of data used in whole-genome analysis requires fine-tuned statistical calculations. The research team is eager to develop new methods in this area.
Read the news release here.
Molecular Psychiatry advance online publication 6 June 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/9/06
Shape-Shifting Protein Controls Assembly of Cell Anchor Points
A team of Johns Hopkins researchers has uncovered how proteins involved in keeping cells anchored in tissues control their binding to each other. By examining the proteins with specialized microscopes, the researchers observed that coaxing a protein to change its shape can change and control how quickly and where in a cell it interacts physically with other proteins.
The proteins involved — talin, vinculin and integrin — normally are found at anchor sites in cells called focal adhesions. Focal adhesions allow cells to stick to each other or other surfaces either to stay in place or to provide traction when cells crawl, such as in cancer spread and during wound healing. Talin, vinculin and integrin, through intricate contacts, connect molecules that make up the cell’s internal structure, called the cytoskeleton, with those found on the outside of the cell, called the extracellular matrix.
The researchers — from the departments of Biological Chemistry and Cell Biology at the School of Medicine and the Department of Electrical Engineering at Johns Hopkins University — used fluorescent molecules to tag these proteins in live cells, then used a technique called FRAP, for fluorescence recovery after photobleaching, to study how quickly proteins move toward and bind to each other. Exposing contact regions — focal adhesions — of the cells to bright light causes the fluorescence to fade temporarily. Looking at these focal adhesions before and after photobleaching allows researchers to calculate how long the proteins remain at the contact sites.
By testing normal and mutated proteins, the team found that talin and integrin normally are found bound to each other. Vinculin, however, stays away by binding to itself in a head-to-tail formation, which hides the section of the protein required to interact with the talin-integrin pair.
A shape change in vinculin causes it to lose grip of its tail, exposing the binding region for the talin-integrin complex. According to the researchers, vinculin’s changing shape might play a critical role in carefully controlling the stability and structure of focal adhesions in dynamic cells.
J. Biol. Chem., Vol. 281, Issue 23, 16006-16015, June 9, 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/16/2006
Identification of a Target of the Gene That Causes Familial Parkinson Disease
In the June 16 issue of the Journal of Biological Chemistry, researchers from the Johns Hopkins Institute for Cell Engineering report the identification of a substrate for the parkin gene, a gene associated with the familial form of the neurodegenerative condition Parkinson disease. Mutations in parkin are the most common cause of familial Parkinson disease.
Parkinson disease is caused by the selective loss of a subset of neurons — called dopaminergic neurons — and leads to tremors and loss of muscle control. The parkin gene encodes an enzyme called ubiquitin E3-ligase, which marks certain cellular proteins for destruction. Mutations in the parkin gene are thought to lead to a build-up of proteins that should be destroyed. These neurons die, presumably because they are overwhelmed with excess protein, although this has not yet been shown.
The research team previously had discovered that a protein called AIMP2 is a substrate of parkin, meaning that parkin marks AIMP2, causing it to be destroyed. The researchers also knew that another protein, called Far Up Stream Element Binding Protein-1 (FBP-1), interacts with AIMP2. So they wondered if FBP-1 also is marked for destruction by parkin.
The researchers found that mice mutated to have no functional parkin gene have higher levels of FBP-1 in neurons from the brain stem and cortex. Human brain tissue from Parkinson disease patients also had higher levels of FBP-1 protein. These observations in mouse and human tissue strongly support that the lack of parkin may lead to excess FBP-1.
Using biochemical analysis, the researchers found that parkin does indeed physically interact with the FBP-1 protein, which is subsequently marked for destruction. According to the researchers, the identification of FBP-1 as a second parkin substrate adds to the understanding of how Parkinson disease progresses.
J. Biol. Chem., Vol. 281, Issue 24, 16193-16196, June 16, 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/19/2006
Using –Omics to Identify Potential Her2 Targets
Using a combination of biochemical and computational approaches, researchers in the Johns Hopkins Institute for Basic Biomedical Sciences, McKusick-Nathans Institute for Genetic Medicine, Institute in Multiscale Modeling of Biological Interactions, and High-Throughput Biology Center have identified potential new targets of a protein called Her2 that is implicated in some types of breast cancers. These new targets could provide inroads to developing new drugs or treatments.
Her2 is a protein found on the surface of some cells. (Unlike other related proteins, Her2 does not appear to require an external ligand for activation.) Active Her2 adds chemical phosphates to proteins to transmit signals from neighboring cells through intermediate proteins into the nucleus of a cell, leading to changes in cell behavior, like turning on certain genes, or causing the cell to divide. Turning on too much Her2 has been linked to 20 percent to 30 percent of breast cancers, “where it is associated with a more aggressive course and poorer prognosis,” according to the research team.
To identify other proteins that interact with Her2, the research team looked for changes in the number of phosphates on hundreds of proteins in cultured cells containing activated Her2, cells without activated Her2 and cells with activated Her2 but treated with a chemical inhibitor of Her2. They first used a technique called SILAC, which stands for stable isotope labeling with amino acids in cell culture, to label the proteins in different populations of cells. Then they used a technique called mass spectrometry to measure the sizes and identify the proteins.
A total of 462 proteins were identified: 198 had phosphate groups added and 81 had phosphate groups removed in cells containing activated Her2. To figure out how these proteins fit into known molecular signaling pathways, the researchers merged their data with that in the Human Protein Reference Database, which contains 33,710 reported protein interactions extracted from scientific literature. The team also used something called Bayesian networks, a computer-based system that calculates how an alteration in one protein may affect another and so on. The combination of approaches led to the identification of previously unknown proteins that are affected by Her2 activity, opening doors for future directions of research.
Published online before print June 19, 2006 Proc. Natl. Acad. Sci. USA
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/23/06
Taming the Cell’s Quality Control to Effect Cystic Fibrosis Mutation
Researchers in the Division of Pediatric Respiratory Sciences at the Johns Hopkins School of Medicine have reported that interfering with the cell’s quality control for misshapen proteins can partially restore the missing protein in cells affected with cystic fibrosis. The report was published June 23 in the Journal of Biological Chemistry.
Cystic fibrosis is a condition that causes an exaggerated immune response due to a missing or disabled protein called the cystic fibrosis transmembrane regulator, or CFTR, in the cells along the surface of the airways and gastrointestinal tract. A mutation in the CFTR gene — known as deltaF508-CFTR — causes the protein product to be misfolded and flagged by the cell’s quality control system to be destroyed.
One of the proteins suspected to be involved in shuttling deltaF508-CFTR to the destruction machinery is called VCP. The researchers found more VCP in patients with deltaF508-CFTR than those without, suggesting that the presence of deltaF508-CFTR causes an increased need for and therefore more VCP. Indeed, when the researchers removed VCP from those cells, the cells accumulated high levels of deltaF508-CFTR.
Further examination of these cells showed that some of the accumulated deltaF508-CFTR in cells lacking VCP was able to mature properly and make it to the cell surface. Moreover, removing VCP also turns down the immune response. The researchers hope that both findings will open doors to developing therapies or drugs for treating cystic fibrosis.
J. Biol. Chem., Vol. 281, Issue 25, 17369-17378, June 23, 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/23/06
A Possible Explanation for Mucolipidosis?
Researchers in the Department of Biological Chemistry at Johns Hopkins have found protein-protein interactions that raise a possible new explanation for how mucolipidosis type IV might be caused. The report was published June 23 in the Journal of Biological Chemistry.
Mucolipidosis type IV (MLIV) is an inherited condition that causes nerve degeneration, loss of muscle control and loss of vision. The condition arises from the malfunction of cells’ digestive compartments — called lysosomes — which have been found to be too acidic in patients with MLIV. The culprit behind MLIV is a gene called TRPML1, which makes a protein that normally resides on lysosomes.
The TRPML1 protein and its related family members, TRPML2 and TRPML3, are known as channel proteins, proteins that control the flow of molecules into and out of cells or compartments in cells.
Using fluorescent tags to mark the proteins, the researchers found that both TRPML1 and 2 normally are found on lysosomes. TRPML3, however, requires 1 or 2 to help it find the lysosomes; in cells lacking TRPML1 and 2, TRPML3 ends up in a different part of the cell.
The researchers suggest that MLIV patients missing TRPML1 may not be able to get enough TRPML3 onto lysosomes. The shortage of TRPML3 may contribute to malfunctioning lysosomes and therefore some of the symptoms of MLIV.
J. Biol. Chem., Vol. 281, Issue 25, 17517-17527, June 23, 2006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
NEWS BRIEFS:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/21/06
Johns Hopkins Resident First to Earn New Harvard Medical Genetics Prize
Ronald Cohn, M.D., a resident in the combined pediatrics and genetics program and chief resident at the McKusick-Nathans Institute for Genetic Medicine at Johns Hopkins, has been awarded the first Harvard-Partners Center for Genetics and Genomics Award in medical genetics. Cohn, whose research focuses on muscle regeneration in various muscle diseases, received a $20,000 cash prize at a formal dinner in his honor in Boston on June 21 and presented at grand rounds at Harvard Medical School that same day.
Cohn, the first Hopkins resident to train in a combined pediatric and genetics program, says it is an “incredible honor to be the inaugural recipient” of an award that recognizes the path that medical genetics research is taking.
“The fact that I am now being recognized for things which have given me so much satisfaction and enjoyment is truly beyond anything I could ever have imagined at this stage of my career,” says Cohn. Specifically, his studies are seeking the molecular roots of the muscle deterioration common to a variety of muscle diseases that can cause progressive weakness and disability.
To further his research in neuromuscular disorders, Cohn will join the faculty of pediatrics, neurology and the McKusick-Nathans Institute of Genetic Medicine later this year. He plans to start a clinic for children with decreased muscle tone, known as hypotonia, to provide these children a place for coordinated diagnostic and therapeutic services.
Read the news release here.
McKusick-Nathans Institute of Genetic Medicine
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
6/28/06
Hopkins Postdoctoral Fellows Awarded Damon Runyon Fellowships
Three Johns Hopkins postdoctoral fellows have been awarded Damon Runyon Cancer Research Foundation fellowships. The fellowship lasts three years.
Kate O’Donnell, Ph.D., a 2005 graduate of the Human Genetics and Molecular Biology Ph.D. program, will pursue studies to identify genes that influence liver cancer spread. Her work will be conducted in the laboratory of Jef Boeke in the High Throughput Biology Center at Hopkins. The liver cancer hepatocellular carcinoma is the fifth most common solid tumor worldwide, with low survival rates and few effective therapies. Although genetic and genomic changes have been implicated, the critical alterations that drive tumor spread are not well defined. O’Donnell will use a mammalian mobile genetic element — called an L1 transposon — to make mutations in cultured cells and transgenic mice to identify genes that impart cancer susceptibility. These new genes also may lead to new targets for designing therapies to treat hepatocellular carcinomas.
David Maag, Ph.D. will study the roles a molecular signaling protein called inosital polyphosphate multikinase plays in controlling cell growth and cell division in the laboratory of Solomon Snyder, M.D. in the Department of Neuroscience.
Xiaoyan Zheng, Ph.D. will study a family of proteins called the iHog receptors. iHog receptors are involved in how cells communicate with each other via the protein called Hedgehog. This work will be done in the laboratory of Philip Beachy, Ph.D. in the Molecular Biology and Genetics department.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Find Change and Basics online from a Hopkins computer.
Visit Research WebNotes online.
Read Hopkins press releases online.
Upcoming lectures and seminars are listed on the Science Calendar.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
-- JHM --
