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‘Microsteretcher’ Technique May Advance Parkinson’s Research

microstretcher technique

Researchers have developed a way to closely study the function of a cell’s transportation network, made up of structures called microtubules, that appears to be impaired in people with Parkinson’s disease.

This technique, called “microstretcher,” may help to better understand microtubules’ deficits and their underlying causes in Parkinson’s, as well as to identify new therapeutic targets.

“Our experimental set-up enables us to study the relationship between the deformation of microtubules and their biological functions,” Akira Kakugo, PhD, the study’s senior author at Hokkaido University, in Japan, said in a press release.

The new method was described in the study, “Regulation of Biomolecular-Motor-Driven Cargo Transport by Microtubules under Mechanical Stress,” published in the journal ACS Applied Bio Materials.

Microtubules are hollow tubular structures that provide structure not only to cells, but also form highways to transport molecules and organelles inside cells. This transport is mediated by motor proteins, namely dynein and kinesin, which move in opposite directions along microtubules’ “tracks.”

In nerve cells, microtubules are particularly involved in the transport of vesicles filled with neurotransmitters (chemical messengers used in nerve cell communication) down the axon, or nerve cell fiber, to be released as signals to other nerve cells.

Increasing evidence suggests that defective regulation of microtubules may have a role in the development of a broad range of neurodevelopmental, psychiatric, and neurodegenerative diseases, including Parkinson’s.

Microtubule dysfunction was shown to precede axon transport deficits and death of dopamine-producing nerve cells — a hallmark of Parkinson’s disease. In addition, several Parkinson’s-associated proteins, such as tau, alpha-synuclein, parkinpink1, and LRRK2 regulate or appear to affect microtubule stability.

However, there was no experimental set-up to properly study the transport process in microtubules and the effects of disturbances in that process, until now.

Researchers at Hokkaido University and the National Institute of Information and Communications Technology, in Japan, developed a unique technique to control microtubular physical deformation and observe its effects on their transport function.

The microstretcher consists of a horizontal plate with flexible medium inside, which can be “stretched” or “compressed” using a computer system.

The team first used specific proteins to attach microtubules to the pre-stretched medium in a way that the microtubules lied parallel to the surface area and “stretching” axis. Next, dyneins bound to a fluorescent cargo were added to the microtubules.

With this system, researchers were able to evaluate the effects of stretching and compressing the flexible medium, and consequently straightening and bending the microtubules, in dynein-associated transport.

Results showed that the dynein-cargo moved faster as the microtubules began to bend, but only until the compressive strain reached about 25%, “beyond which the dynein-driven transport is retarded,” the researchers wrote.

From that point onward, the speed of dynein-associated transport started to decrease and eventually the deformation led to microtubule collapse and no dynein movement. Different speeds of motion also were observed along distinct areas of the bended microtubules.

The team noted that dynein’s faster motion in slightly bended, rather than straight, microtubules may be associated with the protein’s “walking-like” movement. Also, they believe these physical characteristics of microtubules may contribute to their functions in regulating many cellular processes.

“This work offers a technical advantage for a systematic study of the correlation between the deformation of MTs [microtubules] and its biological functions, i.e., cargo transport, as well as an opportunity to explore the interaction of deformed MTs with MT-associated proteins such as (…) tau,” the researchers wrote.

This new technique is “expected to help explain the [underlying disease-associated mechanisms] of traumatic brain injury, which mechanically stresses cells, and neurological conditions like Huntington’s and Parkinson’s diseases, in which microtubules are known to malfunction,” said Syeda Rubaiya Nasrin, the study’s first author.

Next, the team hopes to evaluate the effects of microtubule physical deformation in kinesin-driven transport along their “tracks.”

“The more we understand this process, the closer we might get to designing new nature-inspired materials that can act in a similar way,” Kakugo said.

The post ‘Microsteretcher’ Technique May Advance Parkinson’s Research appeared first on Parkinson’s News Today.

How 2 Proteins Affect Pathway Linked to Early Onset Disease Detailed for Possibly 1st Time

early onset study

The significance — physiological and clinical — in the interaction of two proteins known to be associated with early onset Parkinson’s disease, PARKIN and PINK1, is detailed, possibly for a first time, by researchers.

Their study, “Phosphorylation of Parkin at serine 65 is essential for its activation in vivo,” was published in the journal Open Biology.

Mutations in the genes coding for proteins two proteins, PINK1 and PARKIN, are associated with early onset Parkinson’s disease — mutations in the Parkin gene account for about 40 percent of Parkinson’s cases in people below age 45.

PINK1 and PARKIN are thought to play essential roles in protecting the brain against stress.

Researchers at the University of Dundee, in the U.K., previously reported that PINK1 is able to detect damages to the cell’s mitochondria — small cellular organelles that provide energy and are known as the cell’s “powerhouses” — and prevent further damage by activating the PARKIN protein.

This occurs via a PINK1-mediated addition of a chemical switch, called a phosphate group, to an amino acid (the building blocks of proteins) in the PARKIN’s protein sequence called serine 65.

Knowledge of the role of PINK1 and PARKIN play in the brain comes mostly from in vitro laboratory studies, while the in vivo (in a live organism) significance of PINK1-mediated phosphorylation (the adding of a phosphate group) of PARKIN serine 65 remained unknown.

Now, an international team led by these researchers developed a mouse model with an altered serine 65 in the Parkin gene, a change that removed this “molecular switch” and prevented PINK1 from activating the PARKIN protein.

Using this mouse model, researchers showed that not only is serine 65 critical for PARKIN’s activation, but it is also necessary for a “protein degradation marker” (i.e., phosphor-ubiquitin) to accumulate in brain nerve cells.

The loss of serine 65 in the PARKIN protein also resulted in impaired motor and balance in the animals, poorly coordinated limbs and mild cognitive defects shown by the animals’ performance on the beam walk test.

In this test, animals are trained to traverse a narrow beam suspended between a starting platform and their home cage. Researchers record the time necessary to fulfill the task and the number of foot slips.

Given the key mitochondrial functions ascribed to the PINK1–Parkin interaction, researchers investigated if the motor problems observed could be attributed to mitochondrial dysfunction.

They found the mice had impaired mitochondrial integrity in a specific brain region involved in movement control, called the striatum, suggesting that PARKIN serine 65 phosphorylation contributes to mitochondrial integrity there.

Importantly, researchers also reported the first clinical and genetic evidence linking Parkinson’s disease  with mutations at PARKIN serine 65 in two patients.

The first case was a 71-year-old Finnish male, who was diagnosed with early onset Parkinson’s at  age 40 and had no reported family history of the disease.

The second case, a 60 year-old Caucasian woman in the U.S. diagnosed at age 54, was identified from the Parkinson’s Progression Markers Initiative (PPMI) —  an ongoing observational study, coordinated by the Michael J. Fox Foundation, of more than 1,300 volunteer participants both with and without Parkinson’s. Its goal is to validate biomarkers and, over time, identify disease risk factors.

Similar to what occurs in the mouse model, these patients’ PINK1 protein lacks the ability to activate the PARKIN enzyme. “Inactivation of this PINK1 phosphorylation site on Parkin alone is sufficient for humans to develop early onset Parkinson’s disease,” the researchers wrote.

“It was particularly gratifying to see that findings from discovery-based science can have such unexpected relevance in Parkinson’s patients,” Tom McWilliams, the study’s first author, said in a press release.

The study concludes:  “We present the most compelling evidence to date demonstrating the physiological and clinical significance of PINK1-dependent Parkin Ser65 phosphorylation. Furthermore … our research indicates that inactivation of this PINK1 phosphorylation site on Parkin alone is sufficient for humans to develop early onset Parkinson’s disease (PD).”

Researchers now hope to determine how the interplay between PINK1 and PARKIN may affect other pathways in living models of the disease.

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Grape Skin Extract Has Beneficial Effect on Mitochondria in Flies With Parkinson’s

Grape skin extract improves muscle function and extends the lifespan of flies with Parkinson’s disease, a study shows.
The neuroprotective effect of grape skin extract was due to its potential to rescue mitochondria — cells’ powerhouses — from defects caused by the disease.
The study, “Skin extract improves muscle function and extends lifespan of a Drosophila model of Parkinson’s disease through activation of mitophagy,” was published in the journal Experimental Gerontology.
The health benefits of drinking red wine have been widely reported, and evidence is accumulating to suggest that wine consumption has potential value against age-related neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease.
The antioxidant and anti-inflammatory activities of red wine polyphenols, such as resveratrol, have been pointed to as the main reasons for its beneficial effects. But studies also have revealed that resveratrol could prevent the formation of toxic amyloid aggregates that often characterize neurodegenerative diseases.
Besides polyphenols, grape skin and seeds also contain anti-oxidative components, including proanthocyanidine and quarcetin, which may actively contribute to protecting against oxidative stress and mediated tissue injury.
Oxidative stress is an imbalance between the production of free radicals and the ability of cells to detoxify them. These free radicals, or reactive oxygen species, are harmful to the cells and are associated with a number of diseases, including Parkinson’s disease.
Researchers at Stanford University School of Medicine evaluated the effect of dietary supplementation with grape skin extract left from red wine-production in a fly model of Parkinson’s disease.
The flies were genetically engineered to have a mutated version of the PINK1 gene, which is known to be linked to the human disease.
Loss of function of the PINK1 gene led to a significant reduction in flies’ lifespan, from a median time of roughly 18 days down to 11 days. Diet supplementation with 8% grape skin extract improved flies’ survival time to a median of 15 days. A similar improvement was achieved with a high dose of resveratrol.
Further assessments revealed that PINK1 mutated flies had abnormal wing posture, a feature that was partially reversed with 8% and 16% grape skin extract, as well as with a high dose of resveratrol.
These results suggest that grape skin extract have potential to improve survival and prevent indirect flight muscle degeneration, and its beneficial effect is mediated by components other than resveratrol alone.
The researchers found that both treatment with grape skin extract and resveratrol could significantly reduce — by about half — the amount of damaging oxygen reactive elements. In addition, it also could prevent the aggregation of mitochondria in muscle and in dopamine-producing nerve cells, protecting them from dying.
After further experiments the team confirmed that the beneficial impact of grape skin extract was sustained by its protective effect on mitochondria activity, and re-activation of the destruction process of damaged mitochondria.
Collectively, these results suggest that “manipulation of the mitochondrial pathways,” with pharmacological agents or alternative strategies such as grape skin extract, “may prove beneficial to combat Parkinson’s disease,” researchers wrote.
“The various components in grape skin extract may act together in a multi-pronged manner” targeting several damaging mechanisms involved in

Source: Parkinson's News Today

Study Sheds Light on Mechanisms of Protein Involved in Genetic Form of Parkinson’s

parkin protein

Canadian researchers have gained new insight into the activation of a protein that plays an important role in the genetic form of Parkinson’s disease.

Findings were published in the study, “Mechanism of parkin activation by phosphorylation,” published in Nature Structural & Molecular Biology.

Parkinson’s disease is a neurodegenerative disease characterized by the loss of dopamine-producing neurons in the substantia nigra — the part of the brain responsible for movement.

While most cases occur sporadically, approximately 5-10 percent of Parkinson’s cases are caused by genetic mutations. Specifically, mutations in the genes PARK2, which provides instructions for the making of the parkin protein, and PINK1, which provides instructions for the PTEN-induced putative kinase 1 protein, are responsible for an early-onset form of Parkinson’s disease.

Parkin and PINK1 are part of the mitochondrial quality-control system. Mitochondria play a central role in energy production in cells.

Parkin is a type of enzyme, called an ubiquitin ligase, that carries out a process called ubiquitination. Ubiquitination is like a cellular tagging system: By adding an ubiquitin molecule to a protein, it marks it for degradation. As such, parkin plays a role in clearing away defective mitochondria — a process called mitophagy — by marking them for ubiquitination.

To restrict their ubiquitination function, many ubiquitin ligases are auto-inhibited when their activity is not required. In other words, the structure of parkin is designed in such a manner that its activation sites are not exposed to avoid rampant degradation in the cell.

Activation of parkin requires a change in its structure to bring the site where the ubiquitin molecule binds together with the site responsible for transferring this molecule to the mitochondria — thus marking it for degradation.

McGill University researchers, funded by the Michael J. Fox Foundation and the Canadian Institutes of Health Research, used powerful X-ray beams and discovered that this process is initiated when PINK1 starts to accumulate on the mitochondrial outer membrane. Then PINK1 chemically adds phosphate compounds — a process called phosphorylation — to nearby ubiquitin molecules. This catches the attention of parkin, which has an affinity for phosphorylated ubiquitin and proceeds to bind the phosphorylated ubiquitin.

Through a mechanism of activation that involves several changes in structure, parkin is able to receive the ubiquitin molecule and eventually transfer it.

“The results provide a complete picture of the activation of parkin,” the researchers wrote.

Understanding parkin’s structure and how it is activated offers hope for targeting this protein as a therapeutic agent to slow or prevent the progression of Parkinson’s disease.

The post Study Sheds Light on Mechanisms of Protein Involved in Genetic Form of Parkinson’s appeared first on Parkinson’s News Today.

Source: Parkinson's News Today

Defects in Mitochondria May Contribute to Parkinson’s Disease, Study Suggests

mitochondria

Mutations in mitochondria, which result in a shortage of energy, may be an underlying cause of movement difficulties associated with Parkinson’s disease (PD), a study suggests.

The study, “PINK1 Phosphorylates MIC60/Mitofilin to Control Structural Plasticity of Mitochondrial Crista Junctions,” was published in the journal Molecular Cell.

Parkinson’s disease is caused by the death or malfunction of dopaminergic neurons, which regulate muscle movement and coordination. To do their job, these nerve cells require large amounts of energy, provided by mitochondria.

Mitochondria need to move around the cell to reach the place where they are needed to provide the necessary energy to dopaminergic neurons. Inability of mitochondria to do so can have severe consequences.

Researchers have now discovered that an enzyme (protein) called PINK1 plays a key role in mitochondrial function. This enzyme works to stabilize a mitochondrial protein, called MIC60, which is vital for energy production.

To mimic Parkinson’s, the team used fruit flies, whose brains work similarly to humans to control voluntary movement. They tested how several mutations in the PINK1 gene — known to be a cause of familial forms of early-onset Parkinson’s — affected mitochondria function in the flies.

Several of these mutations were highly damaging to the flies, leading to death in adult flies and significantly impairing crawling ability at early developmental stages.

In flies genetically engineered to lack PINK1, reintroducing MIC60 expression restored mitochondria structure and energy production, correcting the flies’ behavioral defects and halting the death of dopaminergic neurons.

“We found that PINK1 is required only in highly energetic regions of the cells,” Xinnan Wang, MD, the study’s lead author and a Stanford neuroscientist, said in a press release.

“This supports the theory that Parkinson’s disease involves local energy shortages inside cells due to mitochochondrial malfunction — and it indicates that targeting mitochondria may have great potential for exploring new therapeutic interventions in Parkinson’s,” she said.

Future research is necessary to discover if mitochondrial structure impairment and function exists in Parkinson’s disease patients and whether it contributes to disease progression.

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Source: Parkinson's News Today