Large Aggregates of ALS Causing Protein Might Help Brain Cells

Large Aggregates of ALS Causing Protein Might Help Brain Cells

Summary: Researchers report the formation of larger, more visible SOD1 aggregates may help to protect brain cells.

Source: UNC Health Care.

Scientists at the UNC School of Medicine have made a significant advance in the understanding of the complex and fatal neurodegenerative disease amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease.

Autopsy studies of ALS patients often reveal the accumulation of large, fibrous aggregates of a protein called SOD1 in disease-affected motor neurons. Researchers have hypothesized that these fibrils are what kill neurons and cause ALS in some people. But in a study published in the Proceedings of the National Academy of Sciences, scientists at the University of North Carolina at Chapel Hill found evidence that these large SOD1 fibrils protect rather than harm neurons.

“This is potentially an important finding not only for ALS research but for neurodegenerative disease research in general, because the formation of fibril aggregates is so common in these diseases,” said senior author Nikolay Dokholyan, PhD, the Michael Hooker Distinguished Professor of Biochemistry and Biophysics at UNC-Chapel Hill.

Large, often fibril-type protein aggregates are in fact the most obvious pathological features of Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, ALS, and other major neurodegenerative diseases. Many of the candidate drugs developed in recent years were designed to clear these protein aggregates. But none of these fibril-targeting strategies have proven effective in large clinical trials. Laboratory studies also have largely failed to prove that large SOD1 fibrils are harmful to neurons.

At the same time, researchers have found that much smaller protein clusters called oligomers – made of only a few copies of these proteins – can be highly toxic to motor neuron-like cells grown in the lab and thus are more likely to be the chief causes of brain-cell death in these diseases.

In a 2016 study, for example, Dokholyan’s lab found evidence that “trimer” structures made of just three copies of the SOD1 protein are toxic to the type of neuron affected in ALS.

For the new study, Dokholyan’s team, including lead author Cheng Zhu, PhD, a postdoctoral researcher in his lab, conducted complicated experiments to compare how trimers affect neurons to how larger fibrils affect neurons.

“One challenge is that the smaller structures such as trimers tend to exist only transiently on the way to forming larger structures,” Zhu said. “But we were able to find an SOD1 mutation that stabilizes the trimer structure and another mutation that promotes the creation of the larger fibrils at the expense of smaller structures. So, we were able to separate the effects of these two species of the protein.”

The researchers expressed the mutant SOD1 proteins in test cells that closely resemble the muscle-controlling neurons killed in ALS. They found – as they did in the 2016 study – that when these cells expressed SOD1 mutants that predominantly form trimers, the cells died much more quickly than control cells containing normal SOD1. The trimer-expressing cells even died more quickly than cells expressing mutant forms of SOD1 that are found in severe hereditary ALS cases.

“Looking at various SOD1 mutants, we observed that the degree of toxicity correlated with the extent of trimer formation,” Zhu said.

On the other hand, the viability of cells containing mutant SOD1 that strongly forms fibrils but suppresses trimers tended to be similar as wild-type SOD1, suggesting that the fibrils are protective, not merely less toxic.

This suggests SOD1 fibrils aren’t the problem in SOD1-linked ALS; they might be a solution. “Taking a drug to promote fibril formation could be one way to reduce toxicity in SOD1-ALS,” Dokholyan said.

sod1

An alternative strategy, he noted, would be to limit the formation of trimers or other small, toxic SOD1 oligomers. SOD1 normally works in cells as a two-copy structure, a dimer. Trimers and other abnormal structures appear to originate when the dimers fall apart. So Dokholyan and colleagues are looking for potential drug molecules that can stabilize the dimers.

SOD1 is linked to a significant proportion of ALS cases. Mutations in the SOD1 gene account for about 12 percent of ALS cases that run in families. All of these mutations destabilize the protein’s normal structure and promote abnormal SOD1 structures. SOD1 mutations also appear to account for about 1.5 percent of cases that do not obviously run in families.

“Although SOD1-associated ALS represents a small fraction of all ALS cases, uncovering the origins of neurotoxicity in SOD1 aggregation may shed light on the underlying causes of an entire class of neurodegenerative diseases,” Dokholyan said. The next steps for Dokholyan’s lab is to pinpoint downstream cellular mechanisms of toxicity of pathological trimeric SOD1 and find drugs that mitigate the formation of trimers.

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Other authors include Mohanish Deshmuhk, PhD, professor of cell biology and physiology and member of the UNC Neuroscience Center; research technician Matthew Beck of the Deshmukh lab; and Jack Griffith, PhD, Kenan Distinguished Professor of Microbiology & Immunology and Biochemistry. Dokholyan, Deshmuhk, and Griffith are members of the UNC Lineberger Comprehensive Cancer Center.

Funding: The National Institutes of Health funded this work.

Source: Mark Derewicz – UNC Health Care
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is credited to Dokholyan Lab (UNC School of Medicine).
Original Research: Abstract for “Large SOD1 aggregates, unlike trimeric SOD1, do not impact cell viability in a model of amyotrophic lateral sclerosis” by Cheng Zhu, Matthew V. Beck, Jack D. Griffith, Mohanish Deshmukh and Nikolay V. Dokholyan in PNAS. Published April 16 2018.
doi:10.1073/pnas.1800187115

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UNC Health Care “Large Aggregates of ALS Causing Protein Might Help Brain Cells.” NeuroscienceNews. NeuroscienceNews, 16 April 2018.
<http://neurosciencenews.com/sod1-brain-health-8815/&gt;.

Abstract

Large SOD1 aggregates, unlike trimeric SOD1, do not impact cell viability in a model of amyotrophic lateral sclerosis

Aberrant accumulation of misfolded Cu, Zn superoxide dismutase (SOD1) is a hallmark of SOD1-associated amyotrophic lateral sclerosis (ALS), an invariably fatal neurodegenerative disease. While recent discovery of nonnative trimeric SOD1-associated neurotoxicity has suggested a potential pathway for motor neuron impairment, it is yet unknown whether large, insoluble aggregates are cytotoxic. Here we designed SOD1 mutations that specifically stabilize either the fibrillar form or the trimeric state of SOD1. The designed mutants display elevated populations of fibrils or trimers correspondingly, as demonstrated by gel filtration chromatography and electron microscopy. The trimer-stabilizing mutant, G147P, promoted cell death, even more potently in comparison with the aggressive ALS-associated mutants A4V and G93A. In contrast, the fibril-stabilizing mutants, N53I and D101I, positively impacted the survival of motor neuron-like cells. Hence, we conclude the SOD1 oligomer and not the mature form of aggregated fibril is critical for the neurotoxic effects in the model of ALS. The formation of large aggregates is in competition with trimer formation, suggesting that aggregation may be a protective mechanism against formation of toxic oligomeric intermediates.

Alcohol Dependent People May Lack Important Enzyme

Alcohol Dependent People May Lack Important Enzyme

Summary: Researchers identify a role for the enzyme PRDM2 in alcoholism.

Source: Linköping University

A research group under the leadership of Linköping University Professor Markus Heilig has identified an enzyme whose production is turned off in nerve cells of the frontal lobe when alcohol dependence develops. The deficiency in this enzyme leads to continued use of alcohol despite adverse consequences.

The discovery is now published in the number-one ranked psychiatric journal from the Nature Publishing Group, and could mean completely new possibilities for treating alcoholism.

“We’ve worked hard for this. The enzyme, PRDM2, has previously been studied in cancer research, but we didn’t know that it has a function in the brain,” says Markus Heilig, professor of psychiatry and head of the Center for Social and Affective Neuroscience (CSAN) at Linköping University.

He and his research group are linking together research into alcoholism and other addictive illnesses with advanced brain research. It has long been suspected that people with alcohol dependence have impaired function in the frontal lobes of the brain, but the underlying biological mechanisms have not been known. The research team behind the paper, which includes researchers from both Linköping University and University of Miami, is the first to identify this molecular mechanism.

If frontal function is impaired, it is difficult for us to control our impulses. A person with intact impulse control can walk past a bar on a warm day and think ‘A beer would be nice, but I can’t have one now because I have to get back to work’. An alcoholic does not have sufficient impulse control to refrain, thinking: ‘It’s hot and I’m thirsty’.

“PRDM2 controls the expression of several genes that are necessary for effective signalling between nerve cells. When too little enzyme is produced, no effective signals are sent from the cells that are supposed to stop the impulse,” Professor Heilig tells us.

Several years of dedicated research lie behind this breakthrough. The research, in which Dr Estelle Barbier – post-doctoral fellow at CSAN – had a central role, has shown that alcohol dependence in rats leads to a down-regulation of PRDM2 production, which in turn leads to disruption of impulse control. This is why the laboratory animals continue to consume alcohol, even when it is unpleasant. If they are subjected to stress, they also quickly relapse into drinking alcohol.

Image shows a man drinking beer.

In the next step, the researchers knocked out the production of PRDM2 in the frontal lobes of rats that were not dependent, and they observed the same behaviour – impulse control was disrupted.

“We see how a single molecular manipulation gives rise to important characteristics of an addictive illness. Now that we’re beginning to understand what’s happening, we hope we’ll also be able to intervene. Over the long term, we want to contribute to developing effective medicines, but over the short term the important thing, perhaps, is to do away with the stigmatisation of alcoholism,” Professor Heilig says.

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LiU researchers have worked together with colleagues including Professor Claes Wahlestedt and his co-workers at Miami University.

Source: Monica Westman Svenselius – Linköping University 
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Full open access research for “Dependence-induced increase of alcohol self-administration and compulsive drinking mediated by the histone methyltransferase PRDM2” by Barbier E, Johnstone AL, Khomtchouk BB, Tapocik JD, Pitcairn C, Rehman F, Augier E, Borich A, Schank JR, Rienas CA, Van Booven DJ, Sun H, Nätt D, Wahlestedt C, and Heilig M in Molecular Psychiatry. Published online August 30 2016 doi:10.1038/MP.2016.131

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Linköping University “Alcohol Dependent People May Lack Important Enzyme.” NeuroscienceNews. NeuroscienceNews, 4 September 2016.
<http://neurosciencenews.com/alcoholism-enzyme-prdm2-4960/&gt;.

Abstract

Dependence-induced increase of alcohol self-administration and compulsive drinking mediated by the histone methyltransferase PRDM2

Epigenetic processes have been implicated in the pathophysiology of alcohol dependence, but the specific molecular mechanisms mediating dependence-induced neuroadaptations remain largely unknown. Here, we found that a history of alcohol dependence persistently decreased the expression of Prdm2, a histone methyltransferase that monomethylates histone 3 at the lysine 9 residue (H3K9me1), in the rat dorsomedial prefrontal cortex (dmPFC). Downregulation of Prdm2 was associated with decreased H3K9me1, supporting that changes in Prdm2 mRNA levels affected its activity. Chromatin immunoprecipitation followed by massively parallel DNA sequencing showed that genes involved in synaptic communication are epigenetically regulated by H3K9me1 in dependent rats. In non-dependent rats, viral-vector-mediated knockdown of Prdm2 in the dmPFC resulted in expression changes similar to those observed following a history of alcohol dependence. Prdm2 knockdown resulted in increased alcohol self-administration, increased aversion-resistant alcohol intake and enhanced stress-induced relapse to alcohol seeking, a phenocopy of postdependent rats. Collectively, these results identify a novel epigenetic mechanism that contributes to the development of alcohol-seeking behavior following a history of dependence.


PRDM2

This tumor suppressor gene is a member of a nuclear histone/protein methyltransferase superfamily. It encodes a zinc finger protein that can bind to retinoblastoma protein, estrogen receptor, and the TPA-responsive element (MTE) of the heme-oxygenase-1 gene. Although the functions of this protein have not been fully characterized, it may (1) play a role in transcriptional regulation during neuronal differentiation and pathogenesis of retinoblastoma, (2) act as a transcriptional activator of the heme-oxygenase-1 gene, and (3) be a specific effector of estrogen action. Three transcript variants encoding different isoforms have been found for this gene.[4]

Interactions

PRDM2 has been shown to interact with Estrogen receptor alpha[5] and Retinoblastoma protein.

Salt and protein to sleep and blame ‘Food Coma’ on the brain

I consumed Trader Joe’s chocolate cake for 4 servings last night with 28 grams of sugar which woke me up from 12 midnight to 3 am. Salt and protein has an effect on the brain to go back to sleep as described in this fruit fly study and one author’s regimen of combo of salt and sugar under the tongue. Caffeine in chocolate is negligible to have an effect but might have stronger effect on others.

Connie

In the book Eat for Heat, researcher Matt Stone describes this trick we mentioned above as a solution to help you sleep better.

“The mix of salt and sugar is absolutely necessary for stressful situations during the night. When insomnia occurs between 2 am and 4 am accompanied by a feeling of excess adrenaline flowing through your body (adrenaline spikes during this time), salt and sugar under the tongue is the only way forward.”

Blame ‘Food Coma’ On The Brain

Summary: Researchers investigate fruit fly brains to discover the connection between eating, sleep and activity.

Source: Bowling Green State University.

The humble fruit fly has proved to be a fruitful research subject for BGSU neuroscientist Dr. Robert Huber and colleagues from Scripps Research Institute in Florida and elsewhere. The collaborators’ research into their behavior has helped expand our understanding of some important neurobiological connections between eating and sleep — including the infamous “food coma” felt after a big meal.

The Scripps study was one of Huber’s projects as a fellow at the Radcliffe Institute for Advanced Studies at Harvard University in Cambridge, Mass., last year. As an expert in computational ethology, he uses computer technology to obtain meaningful numbers from complex systems — in this case, capturing and precisely recording the tiny Drosophilas’ behavior related to eating, activity levels and sleep.

The cause of the food coma turned out to be protein and salt, along with the time of day the food was consumed. Surprisingly, sugar did not seem to play a role, according to the study. The results of the experiments Huber conducted with lead researcher Dr. William Ja of Scripps and his team were reported in more than 200 newspapers around the world.

The scientists will now look more deeply at the brain structures that induce the insects to sleep after consuming protein and salt, and test theories about why sleep then would be beneficial.

“Clearly, protein is a very expensive commodity,” Huber said. “If sleep increases your ability to resorb it, that would be a possible reason. And the same thing with salt.” Carbohydrates, on the other hand, are much easier to come by in nature, he said, so might not call for such dedicated digestion.

The fruit flies’ preference for protein does explain their attraction to overripe fruit, where they can lay their eggs.

“The flies have very good sensory receptors to detect all kinds of volatile compounds that indicate ripe fruit and yeast,” Huber said.

Huber’s interest in computer ethology is tied to his fascination with the connection between genetics and behavior, first discovered and explored by the late molecular biologist Seymour Benzer, with whom Ja conducted postdoctoral research. Huber has also been working with other labs on projects utilizing video tracking and had an article in the journal PLoS One in 2012 about developing better technology to look at the activity patterns of fruit flies. His primary projects as a Radcliffe fellow are with Dr. Ed Kravitz of Harvard Medical School, examining addiction and aggression in Drosophila.

A shared interest in behavioral genetics is what also drew Huber to the Ja team’s work.

“Ja has always been interested in the connection between behavior and genetics,” Huber said. “And their lab is just phenomenal. The real advantage of the fruit flies is you have such exquisite control over all the different bits of their genes and there’s so much you can do with them.

“You can express a certain gene in a certain subtype of neurons. Mushroom bodies (a pair of brain structures having to do with learning and memory) have dopaminergic neurons only to do with short-term memory and others for long-term memory. You can put those specific neurons under the control of optigenetics by expressing a membrane channel, related to a photoreceptor. So when you shine a red light onto the fly’s head it opens up channels which specifically activate the entire subset of neurons for long-term memory, for instance. There’s no other model system where you can gain that level of control.”

Huber’s expertise with video tracking and applying computer vision to monitor and measure the tiny flies’ behavior allowed the researchers to collect much more reliable data “than having an observer there with a clipboard, writing a summary of what happens,” he said. “Instead, we apply computer technology with strict rules to objectively remove observer bias. Behavior is a very complex type of trait or phenotype, so it’s not as simple as measuring the height of something. We use computer technology with video tracking, integrating it with sensors and robotic interfaces. We can create automated learning paradigms in real time.”

Thus, a system devised by Huber senses when a fruit fly alights on a tiny platform and reaches up to eat from a tube. The computer measures exactly the number and duration of instances of feeding along with a record of the fly’s activity levels, including those that denote sleep.

“We can really improve our characterization of food consumption and activity,” Huber said. “In one second, we can get a thousand data points, very accurately, showing when, how much, how often they feed. That’s not something you are able to do by hand.”

During the food coma, the flies remain still for a certain amount of time and they are much less responsive to any kind of other cues than they would normally be, he said.

“There’s clearly something very potent about sleep itself,” Huber said. Using genetic manipulation techniques, the team will look at whether a neuron with a receptor for a neuropeptide called leucokinin is actually playing a role in causing the flies to fall asleep specifically after consuming protein and salt.

“You can turn those receptors on and off with molecular genetics and piece together how the whole network that controls sleep is put together,” Huber said.

This should help reveal more about the mechanics of sleeping and eating. Using a tiny but extremely powerful LED light, he is able to trigger responses in the genetically modified flies. When the light is not activated, the insects behave just like any other normal fruit fly.

Huber is also eager to explore the potential of the video tracking technology for “tying together metabolic physiology and how much animals eat, what they eat, and how they convert that into energy, and what that has to do with aging,” he said, noting that appetite and satiety, sleep patterns, aging and other functions are all controlled by neurosignals. Anything that interferes with one signal will affect something else. Another of his related projects is with Dr. Leslie Griffith at Brandeis University, regarding food choices, activity patterns and “clock genes.”

After spending several months observing the fruit flies up close, Huber said he has a new appreciation for them.

“They’re very intricate little ‘critters,’” he said. “I spent quite a few days at first just watching them, and their behavior is a lot more complex than what we might think. I did not appreciate them before going there.

a fruit fly.

“Flies are very good at learning,” he added. Additional research into those individuals who are not good at it has identified which genes are altered in these “behavioral mutants.” In collaboration with BGSU colleagues Drs. Moira van Staaden, biological sciences, and Jon Sprague, director of the Ohio Attorney General’s Center for the Future of Forensic Science, he plans to study the role these genes play as flies learn sensory cues paired with human drugs of abuse.

Following his return from Boston, Huber described his sabbatical as “phenomenal, I got to work with a whole group of scholars on so many interesting projects; it was so stimulating.” And having open access to “maker spaces” in Cambridge’s Central Square, halfway between Harvard and MIT, he created his very tiny electronic devices for improving precision — “I was like a kid in the candy store. I’m still very excited about it.”

The fruit flies have inspired not only scientific but also art projects. Huber is collaborating on a “fruit fly soundscape” that arose from his new friendship with Radcliffe fellow Reiko Yamada. A sound artist, classical pianist, experimental composer and now artist in residence at the Institute for Electronic and Acoustic Music at the University of Music and Performing Arts in Graz, Austria, Yamada was “really mesmerized by the difference in scale we live in between the fruit flies and humans,” Huber said. Their interactive soundscape will debut at the IEM Cube at the end of March.

In addition, Huber is collaborating with his former adviser Dr. Kent Rylander, now turned jazz musician since his retirement from Texas Tech University 15 years ago. Huber and Rylander are pursuing a project on the aesthetics, compositional patterns and improvisation of birdsong.

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Source: Bowling Green State University 
Image Source: NeuroscienceNews.com image is credited to Mr.checker and is licensed CC BY SA 3.0.
Original Research: Full open access research for “Postprandial sleep mechanics in Drosophila” by Keith R Murphy, Sonali A Deshpande, Maria E Yurgel, James P Quinn, Jennifer L Weissbach, Alex C Keene, Ken Dawson-Scully, Robert Huber, Seth M Tomchik, and William W Ja in eLife. Published online November 22 2016 doi:10.7554/eLife.19334

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Bowling Green State University “Blame ‘Food Coma’ On The Brain.” NeuroscienceNews. NeuroscienceNews, 9 January 2017.
<http://neurosciencenews.com/food-coma-neuroscience-5899/&gt;.

Abstract

Postprandial sleep mechanics in Drosophila

Food consumption is thought to induce sleepiness. However, little is known about how postprandial sleep is regulated. Here, we simultaneously measured sleep and food intake of individual flies and found a transient rise in sleep following meals. Depending on the amount consumed, the effect ranged from slightly arousing to strongly sleep inducing. Postprandial sleep was positively correlated with ingested volume, protein, and salt—but not sucrose—revealing meal property-specific regulation. Silencing of leucokinin receptor (Lkr) neurons specifically reduced sleep induced by protein consumption. Thermogenetic stimulation of leucokinin (Lk) neurons decreased whereas Lk downregulation by RNAi increased postprandial sleep, suggestive of an inhibitory connection in the Lk-Lkr circuit. We further identified a subset of non-leucokininergic cells proximal to Lkr neurons that rhythmically increased postprandial sleep when silenced, suggesting that these cells are cyclically gated inhibitory inputs to Lkr neurons. Together, these findings reveal the dynamic nature of postprandial sleep.

“Postprandial sleep mechanics in Drosophila” by Keith R Murphy, Sonali A Deshpande, Maria E Yurgel, James P Quinn, Jennifer L Weissbach, Alex C Keene, Ken Dawson-Scully, Robert Huber, Seth M Tomchik, and William W Ja in eLife. Published online November 22 2016 doi:10.7554/eLife.19334

Fresh raw marijuana nutrition facts

cannaFresh raw marijuana is a complete food source.

It can be eaten in salads or juiced.

No other single plant source has the essential amino acids in such an easily digestible form that provides instant food energy.

Fresh raw marijuana contains all the essential amino acids and fatty acids necessary in maintaining healthy human life. Fresh raw marijuana has the perfect 3-1 ratio of omega 6 and 3 fatty acids.

Fresh raw marijuana has an abundant supply of nutrients like magnesium, Phytosterols, Ascorbic Acid, Beta Carotene, Calcium, Folic Acid, Fiber, Iron, Potassium, Phosphorus, Zinc, Riboflavin, Niacin and Thiamine.

Fresh raw marijuana is also rich in vitamin A, E, D and B12.

The Amino Acids in fresh raw marijuana is an excellent source of digestible protein.

BENEFITS

Fresh raw marijuana is beneficial for skin conditions like sunburn, acme, eczema and psoriasis. Fresh raw marijuana rejuvenates the skin.

Fresh raw marijuana relieves symptoms of PMS and is an effective anti-inflammatory that provides pain relieve from arthritis.

Fresh raw marijuana provides instant energy and reduces fatigue.

Fresh raw marijuana improves memory, concentration and alertness.

Fresh raw marijuana improves emotional stability and cognitive abilities. Fresh raw marijuana also increases learning abilities.

Fresh raw marijuana will prevent disease and boost your immune system.

The big question is where do I get my hands on fresh raw marijuana?

Well you pretty much have to grow your own if it can be done legally.

Grow your herb organically under full spectrum light for best results. Natural sunlight produces the best medicine. Some growers grow organically in a healthy growing environment but not all growers grow for the same reasons so find a grower that can provide you with the quality you are looking for.

“The Medical Marijuana Guide. NATURES PHARMACY.” has more information on fresh raw marijuana and how fresh raw marijuana can benefit you as a source of nutrition and medicine.

Brain injury, concussive force of military blasts and Alzheimer’s – tau protein

Tau proteins (or τ proteins, after the Greek letter with that name) are proteins that stabilize microtubules. They are abundant in neurons of the central nervous system and are less common elsewhere, but are also expressed at very low levels in CNS astrocytes and oligodendrocytes.[5] Pathologies and dementias of the nervous system such as Alzheimer’s disease and Parkinson’s disease [6] are associated with tau proteins that have become defective and no longer stabilize microtubules properly.

The tau proteins are the product of alternative splicing from a single gene that in humans is designated MAPT(microtubule-associated protein tau) and is located on chromosome 17.[7][8]

The tau proteins were identified in 1975 as heat stable proteins essential for microtubule assembly [9][10] and since then, they have been characterized as intrinsically disordered proteins.[11]

Neurons were grown in tissue culture and stained with antibody to MAP2 protein in green and MAP tau in red using the immunofluorescence technique. MAP2 is found only in dendrites and perikarya, while tau is found not only in the dendrites and perikarya but also in axons. As a result, axons appear red while the dendrites and perikarya appear yellow, due to superimposition of the red and green signals. DNA is shown in blue using the DAPI stain which highlights the nuclei.

Function

Tau protein is a highly soluble microtubule-associated protein (MAP). In humans, these proteins are found mostly in neurons compared to non-neuronal cells. One of tau’s main functions is to modulate the stability of axonal microtubules. Other nervous system MAPs may perform similar functions, as suggested by tau knockout mice that did not show abnormalities in brain development – possibly because of compensation in tau deficiency by other MAPs.[12] Tau is not present in dendrites and is active primarily in the distal portions of axons where it provides microtubule stabilization but also flexibility as needed. This contrasts with MAP6 (STOP) proteins in the proximal portions of axons, which, in essence, lock down the microtubules and MAP2 that stabilizes microtubules in dendrites.

Tau proteins interact with tubulin to stabilize microtubules and promote tubulin assembly into microtubules.[10]Tau has two ways of controlling microtubule stability: isoforms and phosphorylation.

Structure

Six tau isoforms exist in human brain tissue, and they are distinguished by their number of binding domains. Three isoforms have three binding domains and the other three have four binding domains. The binding domains are located in the carboxy-terminus of the protein and are positively charged (allowing it to bind to the negatively charged microtubule). The isoforms with four binding domains are better at stabilizing microtubules than those with three binding domains. The isoforms are a result of alternative splicing in exons 2, 3, and 10 of the tau gene.

Tau is a phosphoprotein with 79 potential Serine (Ser) and Threonine (Thr) phosphorylation sites on the longest tau isoform. Phosphorylation has been reported on approximately 30 of these sites in normal tau proteins.[13]

Phosphorylation of tau is regulated by a host of kinases, including PKN, a serine/threonine kinase. When PKN is activated, it phosphorylates tau, resulting in disruption of microtubule organization.[14]

Phosphorylation of tau is also developmentally regulated. For example, fetal tau is more highly phosphorylated in the embryonic CNS than adult tau.[15] The degree of phosphorylation in all six isoforms decreases with age due to the activation of phosphatases.[16] Like kinases, phosphatases too play a role in regulating the phosphorylation of tau. For example, PP2A and PP2B are both present in human brain tissue and have the ability to dephosphorylate Ser396.[17] The binding of these phosphatases to tau affects tau’s association with MTs.

Genetics

In humans, the MAPT gene for encoding tau protein is located on chromosome 17q21, containing 16 exons.[citation needed] The major tau protein in the human brain is encoded by 11 exons.[citation needed] Exons 2, 3 and 10 are alternatively spliced, allowing six combinations (2310; 2+310; 2+3+10; 2310+; 2+310+; 2+3+10+). Thus, in the human brain, the tau proteins constitute a family of six isoforms with the range from 352-441 amino acids. They differ in either zero, one, or two inserts of 29 amino acids at the N-terminal part (exon 2 and 3), and three or four repeat-regions at the C-terminal part (exon 10). So, the longest isoform in the CNS has four repeats (R1, R2, R3 and R4) and two inserts (441 amino acids total), while the shortest isoform has three repeats (R1, R3 and R4) and no insert (352 amino acids total).

The MAPT gene has two haplogroups, H1 and H2, in which the gene appears in inverted orientations. Haplogroup H2 is common only in Europe and in people with European ancestry. Haplogroup H1 appears to be associated with increased probability of certain dementias, such as Alzheimer’s disease. The presence of both haplogroups in Europe means that recombination between inverted haplotypes can result in the lack of one of the functioning copy of the gene, resulting in congenital defects.[18][19][20][21]

Clinical significance

Hyperphosphorylation of the tau protein (tau inclusions, pTau) can result in the self-assembly of tangles of paired helical filaments and straight filaments, which are involved in the pathogenesis of Alzheimer’s diseasefrontotemporal dementia, and other tauopathies.[22]

All of the six tau isoforms are present in an often hyperphosphorylated state in paired helical filaments from Alzheimer’s disease brain. In other neurodegenerative diseases, the deposition of aggregates enriched in certain tau isoforms has been reported. When misfolded, this otherwise very soluble protein can form extremely insoluble aggregates that contribute to a number of neurodegenerative diseases.

Recent research suggests that tau may be released extracellularly by an exosome-based mechanism in Alzheimer’s disease.[23][24]

Gender-specific tau gene expression across different regions of the human brain has recently been implicated in gender differences in the manifestations and risk for tauopathies.[25]

Some aspects of how the disease functions also suggest that it has some similarities to prion proteins.[26]

Traumatic brain injury

Repetitive mild traumatic brain injury (TBI) is now recognized as a central component of brain injury in contact sports, especially American football,[27][28] and the concussive force of military blasts.[29] It can lead to chronic traumatic encephalopathy (CTE) that is characterized by fibrillar tangles of hyperphosphorylated tau.[30]

High levels of tau protein in fluid bathing the brain are linked to poor recovery after head trauma.[31]

Tau hypothesis of Alzheimer’s disease

The tau hypothesis states that excessive or abnormal phosphorylation of tau results in the transformation of normal adult tau into PHF-tau (paired helical filament) and NFTs (neurofibrillary tangles). Tau protein is a highly soluble microtubule-associated protein (MAP).[10] Through its isoforms and phosphorylation tau protein interacts with tubulin to stabilize microtubule assembly. All of the six tau isoforms are present in an often hyperphosphorylated state in paired helical filaments from AD.

Mutations that alter function and isoform expression of tau lead to hyperphosphorylation. The process of tau aggregation in the absence of mutations is not known but might result from increased phosphorylation, protease action or exposure to polyanions, such as glycosaminoglycans.[6] Hyperphosphorylated tau disassembles microtubules and sequesters normal tau, MAP 1(microtubule associated protein1), MAP 2, and ubiquitin into tangles of PHFs. This insoluble structure damages cytoplasmic functions and interferes with axonal transport, which can lead to cell death.

Meet the syndicate: Assassin, accomplices, stooges

Even though p-tau showed the strongest correlation with cognitive decline, and amyloid-beta only a slight correlation, that doesn’t mean that p-tau is committing the crime inside cells all by itself while amyloid loiters in spaces outside of cells in large gangs, creating a distraction. Mitchell’s data analysis has pointed to dynamics more enmeshed than that.

“Though the study had clear trends, it also had a good bit of variance that would indicate multiple factors influencing outcomes,” Mitchell said. And a particular manifestation of amyloid-beta has piqued the researchers’ ire.

Little pieces are water soluble, that is, not tied up in clumps of plaque. The data has shown that these tiny amyloids may be up to no good. After p-tau levels, the study revealed that those of soluble amyloid-beta had the second-strongest correlation with cognitive decline.

“Lumpy amyloid-beta, the stuff we see, ironically doesn’t correlate as well as with cognitive decline the soluble amyloid,” Mitchell said. “The amyloid you don’t see is like the sugar in your tea that dissolves and hits your taste buds versus the insoluble amyloid, which is more like the sugar that doesn’t dissolve and stays at the bottom of the cup.”

Some Alzheimer’s researchers have cited evidence indicating that free-floating amyloid helps produce the corrupted p-tau via a chain of reactions that centers around GSK3 (Glycogen synthase kinase 3), an enzyme that arms tau with phosphorous, turning it into a potential biochemical assassin.

Incidentally, Mitchell’s study also looked at un-phosphorylated tau and found its levels do not correlate with cognitive decline. “That makes sense,” Mitchell said. “Regular tau is the backbone of our neurons, so it has to be there.”

Also, p-tau is a normal part of healthy cells, but in Alzheimer’s it is wildly overproduced.

Massive dataset: 528 mice rat out p-tau

One advantage of data mining 51 existing studies versus doing one new lab experiment, is that the cumulative analysis adds the sample sizes of so many studies together for a whopping grand total. Mitchell’s analysis encompassed results from past experiments carried out on, all totaled, 528 Alzheimer’s mice.

A previous study Mitchell led had already indicated that amyloid-beta plaque levels may not be the most productive target for drug development. Separate reports by other researchers on failed human trials of drugs that fought plaque would seem to corroborate this.

neurons

Mitchell’s prior analysis examined lab studies that used an Alzheimer’s lab mouse model that did not allow for the study of p-tau. Mitchell’s current analysis covered studies involving a different mouse model that did allow for the observation of p-tau.

Mitchell’s latest findings have corroborated the prior study’s findings on amyloid, and also added p-tau as a key suspect in cognitive decline.

Principal investigator: My take on possible treatments

To arrive at the 51 studies with data suitable for inclusion in their analysis, Mitchell’s research team sifted through hundreds of Alzheimer’s research papers, and over time, Mitchell has examined a few thousand herself. She has gained some impressions of how biomedical research may need to tackle the disease’s slippery biochemical labyrinth.

“When we see multifactorial diseases, we tend to think we’ll need multifactorial treatments,” Mitchell said. “That seems to be working well with cancer, where they combine chemotherapy with things like immunotherapy.”

Also, Alzheimer’s diagnosticians might be wise to their adopt cancer colleagues’ early detection stance, she said, as Alzheimer’s disease appears to start long before amyloid-beta plaque appears and cognitive decline sets in.

Above all, basic research should cast a broader net.

“I think p-tau is going to have to be a big part,” she said. “And it may be time to not latch onto amyloid-beta plaque so much like the field has for a few decades.”

Data Detectives Shift Suspicions in Alzheimer’s from Usual Suspect to Inside Villain

Addictive Nut’s Derivatives Could Help Smokers Break the Nicotine Habit

Addictive Nut’s Derivatives Could Help Smokers Break the Nicotine Habit

Summary: Compound derived from the areca nut could help people to quit smoking, a new study reports.

Source: ACS.

As many as 600 million people in Southeast Asia chew areca nuts with betel leaves, sometimes adding tobacco leaves. Many users are addicted to this harmful “betel quid” preparation, which can create a sense of euphoria and alertness. Yet researchers have now discovered that compounds derived from the nut could help cigarette smokers — as well as betel quid chewers — kick their habits.

The researchers will present their work today at the 253rd National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 14,000 presentations on a wide range of science topics.

“There’s a commonality to the two addictions, so we thought we could develop drugs that target both,” says Roger L. Papke, Ph.D., one of the lead researchers on the project. Fellow lead researcher Nicole A. Horenstein, Ph.D., and Papke, along with Clare Stokes and Marta Quadri, Ph.D., are studying compounds from the areca nut to make new molecules that might work better than existing smoking cessation drugs such as Chantix® (varenicline).

More than 480,000 people die each year in the U.S. from the effects of cigarette smoking, according to the U.S. Centers for Disease Control and Prevention. Prescription smoking cessation drugs currently on the market can work well but can also cause harmful side effects. For example, some patients taking the drug varenicline report having suicidal thoughts, sleepwalking and having cardiovascular problems.

Because of varenicline’s side effects, researchers such as Papke and Horenstein are working on alternatives at the University of Florida. Varenicline reduces nicotine cravings by binding to the same receptors that attach nicotine molecules to brain cells, but it activates those receptors to a lesser degree. Undesirable effects occur because the drug also binds to other nicotine receptors that aren’t involved in addiction, Papke explains. “The molecules that we’re developing are more specific — they do not target those other receptors at all, so our compounds should be safer,” he says.

The idea to study the areca nut came when Papke obtained a headhunter’s sword from Borneo. He learned that the peculiar carvings on its hilt might have been made by someone using betel quid. Quids are prepared by mixing sliced areca nuts with slaked lime (calcium hydroxide), spices or sweets, and in some cases tobacco, and wrapping the concoction in leaves from the betel vine. Quid chewing turns users’ teeth bright red and forces them to spit out a lot of red saliva, which discolors local sidewalks and buildings. Worse, quid use is addictive and leads to serious health effects including oral cancer and cardiovascular issues.

Image shows the nut.

In prior work, Papke and Horenstein studied arecoline, one of the psychoactive alkaloids in the areca nut. They discovered that arecoline stimulates the same brain cell receptors responsible for nicotine addiction but doesn’t stimulate the other types of nicotine receptors.

Now, Horenstein is synthesizing a range of compounds with structures that are slightly different from arecoline. The researchers have found that some of these new compounds also bind to the addiction-related receptors, while leaving the other receptors alone. That means these arecoline analogs may be able to treat addiction to cigarettes or to betel quids without side effects. The next step for Horenstein and Papke is to seek funding so they can test these potential new drugs in animal trials.

ABOUT THIS PSYCHOLOGY RESEARCH ARTICLE

Funding: The researchers acknowledge funding from the U.S. National Institutes of Health.

Source: Katie Cottingham – ACS 
Image Source: NeuroscienceNews.com image is credited to Roger Papke, Ph.D.
Original Research: The study will be presented at American Chemical Society 253rd National Meeting & Exposition.

CITE THIS NEUROSCIENCENEWS.COM ARTICLE
ACS “Addictive Nut’s Derivatives Could Help Smokers Break the Nicotine Habit.” NeuroscienceNews. NeuroscienceNews, 5 April 2017.
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