(Image caption: In brain cancer cells, the protein PARC plays a key role in long-term cell survival. In both images, the red represents the protein cytochrome c, which is released when mitochondria are damaged and trigger apoptosis – cell suicide. At left, injured brain cancer cells exhibit little cytochrome c; they use the protein PARC to degrade the released cytochrome c, allowing the cancer cells to survive. At right, when researchers reduced PARC, cytochrome c accumulated, allowing apoptosis to carry on)

Neurons, brain cancer cells require the same little-known protein for long-term survival

Researchers at the UNC School of Medicine have discovered that the protein PARC/CUL9 helps neurons and brain cancer cells override the biochemical mechanisms that lead to cell death in most other cells. In neurons, long-term survival allows for proper brain function as we age. In brain cancer cells, though, long-term survival contributes to tumor growth and the spread of the disease.

These results, published in the journal Science Signaling, not only identify a previously unknown mechanism used by neurons for their much-needed survival, but show that brain cancer cells hijack the same mechanism for their own survival.

The discovery will lead to new investigations of brain cancer treatments and provides insight into Parkinson’s disease, including a potential new research tool for scientists.

“PARC is very similar to Parkin, a protein that’s mutated in Parkinson’s disease,” said Mohanish Deshmukh, PhD, a professor of cell biology and physiology and senior author of the Science Signaling paper. “We think they might work in tandem to protect neurons.”

If so, researchers can investigate the interplay between these proteins to create better drugs to treat the second-most prevalent neurodegenerative disease after Alzheimer’s disease.

Vivian Gama, PhD, a postdoctoral fellow in Deshmukh’s lab, led the experiments in cell cultures and animal models. First, she used external stimuli to promote the damage of mitochondria – the energy sources for cells. In most cell types, when mitochondria are damaged, they release a protein called cytochrome c, which triggers a cascade of biochemical steps that end in cell death – a process known as apoptosis.

Working with neurons, though, Gama found that the protein PARC/CUL9 blocked this process; it degraded cytochrome c, halted apoptosis, and allowed for long-term cell survival. “In this setting, we want PARC to do that because we want neurons to survive as long as possible,” said Gama, first author of the Science Signaling paper.

Deshmukh, a member of the UNC Neuroscience Center and the UNC Lineberger Comprehensive Cancer Center, said, “In Parkinson’s disease, we know that Parkin targets damaged mitochondria for degradation. However, exactly what happens to the proteins, such as cytochrome c, that are released from the damaged mitochondria has been unknown. Now, we think PARC plays a role in this process.”

Deshmukh and Gama’s work could lead to an alternative way to study Parkinson’s disease. Other researchers have created mouse models that lack the Parkin gene, but Gama said these models don’t have many of the hallmark symptoms that human patients have, making the model less than desirable for researchers. “Our hypothesis is that in the absence of Parkin, PARC still does the job,” Gama said, “as it may allow cells to survive.”

Gama and Deshmukh are now creating a model that lacks both the Parkin and PARC genes.

They will also investigate PARC as a target for cancer treatment.

“We tested several cancer cell lines and found that PARC degrades cytochrome c in medulloblastoma, a cancer of the central nervous system and in neuroblastoma, a cancer of the peripheral nervous system,” Gama said. “Not all cytochrome c is degraded; there are likely other factors involved. But PARC is an important player.”

When Gama and colleagues triggered the apoptotic process in brain cancer cells, they found that PARC allowed the cells to survive. When PARC was inhibited, the cells were more vulnerable to stress and damage, which means they could be more vulnerable to compounds aimed at destroying them.

Deshmukh said, “We show that brain cancer cells co-opt PARC to bypass apoptosis in the same way that neurons do and for the exact same purpose.”

Cinnamon May Be Used to Halt the Progression of Parkinson’s disease

Neurological scientists at Rush University Medical Center have found that using cinnamon, a common food spice and flavoring material, can reverse the biomechanical, cellular and anatomical changes that occur in the brains of mice with Parkinson’s disease (PD). The results of the study were recently published in the June 20 issue of the Journal of Neuroimmune Pharmacology.

“Cinnamon has been used widely as a spice throughout the world for centuries,” said Kalipada Pahan, PhD, study lead researcher and the Floyd A. Davis professor of neurology at Rush. “This could potentially be one of the safest approaches to halt disease progression in Parkinson’s patients.”

“Cinnamon is metabolized in the liver to sodium benzoate, which is an FDA-approved drug used in the treatment for hepatic metabolic defects associated with hyperammonemia,” said Pahan. It is also widely used as a food preservative due to its microbiocidal effect.

Chinese cinnamon (Cinnamonum cassia) and original Ceylon cinnamon (Cinnamonum verum) are two major types of cinnamon that are available in the US.

“Although both types of cinnamon are metabolized into sodium benzoate, by mass spectrometric analysis, we have seen that Ceylon cinnamon is much more pure than Chinese cinnamon as the latter contains coumarin, a hepatotoxic molecule,” said Pahan.

“Understanding how the disease works is important to developing effective drugs that protect the brain and stop the progression of PD,” said Pahan. “It is known that some important proteins like Parkin and DJ-1 decrease in the brain of PD patients.”

The study found that after oral feeding, ground cinnamon is metabolized into sodium benzoate, which then enters into the brain, stops the loss of Parkin and DJ-1, protects neurons, normalizes neurotransmitter levels, and improves motor functions in mice with PD.

This research was supported by grants from National Institutes of Health.

“Now we need to translate this finding to the clinic and test ground cinnamon in patients with PD. If these results are replicated in PD patients, it would be a remarkable advance in the treatment of this devastating neurodegenerative disease,” said Dr. Pahan.

Parkinson’s disease is a slowly progressive disease that affects a small area of cells within the mid-brain known as the substantia nigra. Gradual degeneration of these cells causes a reduction in a vital chemical neurotransmitter, dopamine. The decrease in dopamine results in one or more of the classic signs of Parkinson’s disease that includes: resting tremor on one side of the body; generalized slowness of movement; stiffness of limbs; and gait or balance problems. The cause of the disease is unknown. Both environmental and genetic causes of the disease have been postulated.

Parkinson’s disease affects about 1.2 million patients in the United States and Canada. Although 15 percent of patients are diagnosed before age 50, it is generally considered a disease that targets older adults, affecting one of every 100 persons over the age of 60. This disease appears to be slightly more common in men than women.

Gene-silencing study finds new targets for Parkinson’s disease

Scientists at the National Institutes of Health have used RNA interference (RNAi) technology to reveal dozens of genes which may represent new therapeutic targets for treating Parkinson’s disease. The findings also may be relevant to several diseases caused by damage to mitochondria, the biological power plants found in cells throughout the body.

"We discovered a network of genes that may regulate the disposal of dysfunctional mitochondria, opening the door to new drug targets for Parkinson’s disease and other disorders," said Richard Youle, Ph.D., an investigator at the National Institute of Neurological Disorders and Stroke (NINDS) and a leader of the study. The findings were published online in Nature. Dr. Youle collaborated with researchers from the National Center for Advancing Translational Sciences (NCATS).

Mitochondria are tubular structures with rounded ends that use oxygen to convert many chemical fuels into adenosine triphosphate, the main energy source that powers cells. Multiple neurological disorders are linked to genes that help regulate the health of mitochondria, including Parkinson’s, and movement diseases such as Charcot-Marie Tooth Syndrome and the ataxias.

Some cases of Parkinson’s disease have been linked to mutations in the gene that codes for parkin, a protein that normally roams inside cells, and tags damaged mitochondria as waste. The damaged mitochondria are then degraded by cells’ lysosomes, which serve as a biological trash disposal system. Known mutations in parkin prevent tagging, resulting in accumulation of unhealthy mitochondria in the body.

RNAi is a natural process occurring in cells that helps regulate genes. Since its discovery in 1998, scientists have used RNAi as a tool to investigate gene function and their involvement in health and disease.

Dr. Youle and his colleagues worked with Scott Martin, Ph.D., a coauthor of the paper and an NCATS researcher who is in charge of NIH’s RNAi facility. The RNAi group used robotics to introduce small interfering RNAs (siRNAs) into human cells to individually turn off nearly 22,000 genes. They then used automated microscopy to examine how silencing each gene affected the ability of parkin to tag mitochondria.

"One of NCATS’ goals is to develop, leverage and improve innovative technologies, such as RNAi screening, which is used in collaborations across NIH to increase our knowledge of gene function in the context of human disease," said Dr. Martin.

For this study, the researchers used RNAi to screen human cells to identify genes that help parkin tag damaged mitochondria. They found that at least four genes, called TOMM7, HSPAI1L, BAG4 and SIAH3, may act as helpers. Turning off some genes, such as TOMM7 and HSPAI1L, inhibited parkin tagging whereas switching off other genes, including BAG4 and SIAH3, enhanced tagging. Previous studies showed that many of the genes encode proteins that are found in mitochondria or help regulate a process called ubiquitination, which controls protein levels in cells.

Next the researchers tested one of the genes in human nerve cells. The researchers used a process called induced pluripotent stem cell technology to create the cells from human skin. Turning off the TOMM7 gene in nerve cells also appeared to inhibit tagging of mitochondria. Further experiments supported the idea that these genes may be new targets for treating neurological disorders.

"These genes work like quality control agents in a variety of cell types, including neurons," said Dr. Youle. "The identification of these helper genes provides the research community with new information that may improve our understanding of Parkinson’s disease and other neurological disorders."

The RNAi screening data from this study are available in NIH’s public database, PubChem, which any researcher may analyze for additional information about the role of dysfunctional mitochondria in neurological disorders.

"This study shows how the latest high-throughput genetic technologies can rapidly reveal insights into fundamental disease mechanisms," said Story Landis, Ph.D., director of the NINDS. "We hope the results will help scientists around the world find new treatments for these devastating disorders."

Boosting ‘cellular garbage disposal’ can delay the aging process

UCLA life scientists have identified a gene previously implicated in Parkinson’s disease that can delay the onset of aging and extend the healthy life span of fruit flies. The research, they say, could have important implications for aging and disease in humans.

The gene, called parkin, serves at least two vital functions: It marks damaged proteins so that cells can discard them before they become toxic, and it is believed to play a key role in the removal of damaged mitochondria from cells.

"Aging is a major risk factor for the development and progression of many neurodegenerative diseases," said David Walker, an associate professor of integrative biology and physiology at UCLA and senior author of the research. "We think that our findings shed light on the molecular mechanisms that connect these processes."

In the research, published today in the early online edition of the journal Proceedings of the National Academy of Sciences, Walker and his colleagues show that parkin can modulate the aging process in fruit flies, which typically live less than two months. The researchers increased parkin levels in the cells of the flies and found that this extended their life span by more than 25 percent, compared with a control group that did not receive additional parkin.

"In the control group, the flies are all dead by Day 50," Walker said. "In the group with parkin overexpressed, almost half of the population is still alive after 50 days. We have manipulated only one of their roughly 15,000 genes, and yet the consequences for the organism are profound."

"Just by increasing the levels of parkin, they live substantially longer while remaining healthy, active and fertile," said Anil Rana, a postdoctoral scholar in Walker’s laboratory and lead author of the research. "That is what we want to achieve in aging research — not only to increase their life span but to increase their health span as well."

Treatments to increase parkin expression may delay the onset and progression of Parkinson’s disease and other age-related diseases, the biologists believe. (If parkin sounds related to Parkinson’s, it is. While the vast majority of people with the disease get it in older age, some who are born with a mutation in the parkin gene develop early-onset, Parkinson’s-like symptoms.)

"Our research may be telling us that parkin could be an important therapeutic target for neurodegenerative diseases and perhaps other diseases of aging," Walker said. "Instead of studying the diseases of aging one by one — Parkinson’s disease, Alzheimer’s disease, cancer, stroke, cardiovascular disease, diabetes — we believe it may be possible to intervene in the aging process and delay the onset of many of these diseases. We are not there yet, and it can, of course, take many years, but that is our goal."

'The garbage men in our cells go on strike'

To function properly, proteins must fold correctly, and they fold in complex ways. As we age, our cells accumulate damaged or misfolded proteins. When proteins fold incorrectly, the cellular machinery can sometimes repair them. When it cannot, parkin enables cells to discard the damaged proteins, said Walker, a member of UCLA’s Molecular Biology Institute.

"If a protein is damaged beyond repair, the cell can recognize that and eliminate the protein before it becomes toxic," he said. "Think of it like a cellular garbage disposal. Parkin helps to mark damaged proteins for disposal. It’s like parkin places a sticker on the damaged protein that says ‘Degrade Me,’ and then the cell gets rid of this protein. That process seems to decline with age. As we get older, the garbage men in our cells go on strike. Overexpressed parkin seems to tell them to get back to work."

Rana focused on the effects of increased parkin activity at the cellular and tissue levels. Do flies with increased parkin show fewer damaged proteins at an advanced age? “The remarkable finding is yes, indeed,” Walker said.

Parkin has recently been shown to perform a similarly important function with regard to mitochondria, the tiny power generators in cells that control cell growth and tell cells when to live and die. Mitochandria become less efficient and less active as we age, and the loss of mitochondrial activity has been implicated in Alzheimer’s, Parkinson’s and other neurodegenerative diseases, as well as in the aging process, Walker said.

Parkin appears to degrade the damaged mitochondria, perhaps by marking or changing their outer membrane structure, in effect telling the cell, “This is damaged and potentially toxic. Get rid of it.”

If parkin is good, is more parkin even better?

While the researchers found that increased parkin can extend the life of fruit flies, Rana also discovered that too much parkin can have the opposite effect — it becomes toxic to the flies. When he quadrupled the normal amount of parkin, the fruit flies lived substantially longer, but when he increased the amount by a factor of 30, the flies died sooner.

"If you bombard the cell with too much parkin, it could start eliminating healthy proteins," Rana said.

In the lower doses, however, the scientists found no adverse effects. Walker believes the fruit fly is a good model for studying aging in humans — who also have the parkin gene — because scientists know all of the fruit fly’s genes and can switch individual genes on and off.

Previous research has shown that fruit flies die sooner when you remove parkin, Walker noted.

Walker and Rana do not know what the optimal amount of parkin would be in humans.

While the biologists increased parkin activity in every cell in the fruit fly, Rana also conducted an experiment in which he increased parkin expression only in the nervous system. That, too, was sufficient to make the flies live longer.

"This tells us that parkin is neuroprotective during aging," Walker said. "However, the beneficial effects of parkin are greater — twice as large — when we increased its expression everywhere."

"We were excited about this research from the beginning but did not know then that the life span increase would be this impressive," Rana said.

The image that accompanies this news release shows clumps or aggregates of damaged proteins in an aged brain from a normal fly (left panel) and an age-matched brain with increased neuronal parkin levels (right panel). As can be seen, increasing parkin levels in the aging brain reduces the accumulation of aggregated proteins.

Scientists have found that this kind of protein aggregation occurs in mammals as well, including humans, Rana said.

"Imagine the damage the accumulation of protein trash is doing to the cell," Walker said. "With increased Parkin, the trash has been collected. Without it, the garbage that should be discarded is accumulating in the cells."

Parkin protects from neuronal cell death

Parkinson’s disease is the most common movement disorder and the second most common neurodegenerative disease after Alzheimer’s disease. It is characterized by the loss of dopamin-producing neurons in the substantia nigra, a region in the midbrain, which is implicated in motor control. The typical clinical signs include resting tremor, muscle rigidity, slowness of movements, and impaired balance. In about 10% of cases Parkinson’s disease is caused by mutations in specific genes, one of them is called parkin.

“Parkinson-associated genes are particularly interesting for researchers, since insights into the function and dysfunction of these genes allow conclusions on the pathomechanisms underlying Parkinson’s disease”, says Dr. Konstanze Winklhofer of the Adolf Butenandt Institute at the LMU Munich, who is also affiliated with the German Center for Neurodegenerative Diseases (DZNE). Winklhofer and her colleagues had previously observed that parkin can protect neurons from cell death under various stress conditions. In the course of this project, it became obvious that a loss of parkin function impairs the activity and integrity of mitochondria, which serve as the cellular power stations. In their latest publication, Winklhofer and coworkers uncovered the molecular mechanism that accounts for parkin’s neuroprotective action.

“We discovered a novel signaling pathway that is responsible for the neuroprotective activity of parkin,” Winklhofer reports. The central player of this pathway is a protein called NEMO, which is activated by the enzymatic attachment of a linear chain of ubiquitin molecules. This reaction is promoted by parkin, thereby enabling NEMO to activate a signal cascade, which ultimately leads to the expression of a specific set of genes. Winklhofer’s team identified one essential gene targeted by this pathway, which turned out to code for the mitochondrial protein OPA1. OPA1 maintains the integrity of mitochondria and prevents stress-induced neuronal cell death.

“These findings suggest that strategies to activate this signal pathway or to enhance the synthesis of OPA1 in cells exposed to stress could be of therapeutic benefit,” Winklhofer points out.

The newly identified signal pathway may also be relevant in the context of other neurological conditions that are characterized by the loss of specific neurons. Konstanze Winklhofer and her group are already engaged in further projects designed to determine whether other molecules regulated by this pathway might provide targets for therapeutic interventions.

Removing protein ‘garbage’ in nerve cells may help control 2 neurodegenerative diseases

Neuroscientists at Georgetown University Medical Center say they have new evidence that challenges scientific dogma involving two fatal neurodegenerative diseases — amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD) — and, in the process, have uncovered a possible therapeutic target as a novel strategy to treat both disorders.

The study, posted online in the Journal of Biological Chemistry, found that the issue in both diseases is the inability of the cell’s protein garbage disposal system to “pull out” and destroy TDP-43, a powerful, sometimes mutated gene that produces excess amounts of protein inside the nucleus of a nerve cell, or neuron.

"This finding suggests that if we’re able to ‘rev up’ that clearance machinery and help the cell get rid of the bad actors, it could possibly reduce or slow the development of ALS and FTD," says the study’s lead investigator, neuroscientist Charbel E-H Moussa, MB, PhD. "The potential of such an advance is very exciting." He cautions, though, that determining if this strategy is possible in humans could take many years and will involve teams of researchers.

The way to rev up protein disposal is to add parkin — the cell’s natural disposal units — to brain cells. In this study, Moussa and his colleagues demonstrated in two animal experiments that delivering parkin genes to neurons slowed down ALS pathologies linked to TDP-43.”

Moussa says that his study further demonstrates that clumps known as “inclusions” of TDP-43 protein found inside neuron bodies in both disorders do not promote these diseases, as some researchers have argued.

What happens in both diseases is that this protein, which is a potent regulator of thousands of genes, leaves the nucleus and collects inside the gel-like cytoplasm of the neuron. In ALS, also known as Lou Gehrig’s disease, this occurs in motor neurons, affecting movement; in FTD, it occurs in the frontal lobe of the brain, leading to dementia.

"In both diseases, TDP-43 is over-expressed or mutated, and the scientific debate has been whether loss of TDP-43 in the nucleus or gain of TDP-43 in the cytoplasm is the problem," Moussa says.

"Our study suggests TDP-43 in the cell cytoplasm is deposited there in order to eventually be destroyed — without contributing to disease — and that TDP-43 in the nucleus is causing the damage," he says. "Because so much protein is being produced, the cell can’t keep up with removing these toxic particles in the nucleus and the dumping of them in the cytoplasm. There may be a way to fix this problem."

Moussa has long studied parkin, a molecule best known, when mutated and inactive, for its role in a familial form of Parkinson’s disease. He has studied it in Alzheimer’s disease and other forms of dementia. His hypothesis, which he has demonstrated in several recently published studies, is that parkin could help remove the toxic fragments of amyloid beta protein that builds up in the brains of Alzheimer’s disease patients.

What’s more, he developed a method to clear this amyloid beta when it begins to build up in neurons — a gene therapy strategy he has shown works in rodents. Work continues on this potential therapy.

In this study, Moussa found that parkin “tags” TDP-43 protein in the nucleus with a molecule that takes it from the nucleus and into the cytoplasm of the cell. “This is good. If TDP-43 is in the cytoplasm, it will prevent further nuclear damage and deregulation of genetic materials that determine protein identity,” he says.

"This discovery challenges the dogma that accumulation of TDP-43 in the cytoplasm is," Moussa says. "We think parkin is tagging proteins in the nucleus for destruction, but there just isn’t enough parkin around — compared with over-production of TDP-43 — to do the job."

Moussa says his next research steps will be to inject a drug that activates parkin to see whether that can prolong the lifespan and reduce motor defects in mice with ALS.

(Image: iStock)