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Lewy Bodies Are Made of Much More than Alpha-Synuclein, Study Finds

Lewy bodies

Insoluble alpha-synuclein protein has long been thought to be the main component of Parkinson’s hallmark Lewy bodies, but researchers have now reported these abnormal aggregates are also made of cell membrane fragments, fat-like substances, and other cellular components.

This finding was reported in a study, “Lewy pathology in Parkinson’s disease consists of crowded organelles and lipid membranes,” that was published in the journal Nature Neuroscience.

Parkinson’s disease is a neurodegenerative disorder characterized by selective death of midbrain dopamine-producing neurons due to clustering of a protein called alpha-synuclein in structures commonly known as Lewy bodies.

For decades, scientists have believed that alpha-synuclein fibrils (meaning “small fibers”) were the main component of and at Lewy bodies’ core. However, investigators have now contested such belief after studying postmortem human brain tissue from patients with Parkinson’s disease.

Combining imaging techniques, the researchers were able to re-create the 3D structures of these disease-associated clusters. They found that besides alpha-synuclein, Lewy bodies also have membrane fragments, vesicular structures, and abnormal organelles (organ-like structures found inside cells) such as mitochondria — cells’ powerhouses.

Many, but not all, Lewy bodies with alpha-synuclein within them had protein fibers scattered between membrane fragments and organelles. Importantly, a non-fibrillar form of alpha-synuclein was also found to be intermingled with the other contents of the Lewy bodies.

“We used correlative light and electron microscopy and other advanced light microscopy methods to take a closer look at the brain of deceased Parkinson’s patients and discovered that the Lewy bodies consist mainly of membrane fragments from mitochondria and other organelles, but have in most cases no or only negligible quantities of protein fibrils,” Henning Stahlberg, PhD, professor and researcher at the University of Basel in Switzerland, and one of the study’s senior authors, said in a press release.

“The discovery that alpha-synuclein did not present in the form of fibrils was unexpected for us and the entire research field,” Stahlberg said.

The researchers also found that the bodies carried fat-like substances similar to those found in healthy brain cells, like myelin (nerve cells’ protective fatty layer) or fatty components of cell membranes.

“We present here a new theoretical model in which lipid membrane fragments and distorted organelles together with a non-fibrillar form of [alpha-synuclein] are the main structural building blocks for the formation of Lewy pathology,” the researchers stated.

Several studies have linked disturbances in intracellular movement of molecules and organelles with Parkinson’s disease. In addition, alpha-synuclein has been shown to be capable of disrupting the integrity of mitochondrial membranes, manipulating and reorganizing membrane components, and leading membranes to form vesicles under specific biochemical conditions.

Collectively, the study’s findings support the hypothesis of abnormal movement of organelles as a potential driver of Parkinson’s disease mechanism. Also, they “emphasize the need to consider population heterogeneity of Lewy pathology” and show that lipids (cells’ fatty molecules) could play an important role, the researchers said.

“The questions why it has taken so long to better characterize Lewy bodies can perhaps be answered with the previous sample preparation and electron microscopy methods. Today’s technologies enable us to have a much more detailed look into the morphology of [the] human brain,” Stahlberg said. “The big question for us now is: How does alpha-synuclein contribute to the formation of Lewy bodies, if not present in [the] form of fibrils?”

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Enzyme Linking Fatty Acids to Alpha-synuclein Could Be Parkinson’s Therapeutic Target, Study Suggests

alpha-synuclein, fatty acids

Inhibiting an enzyme that regulates the production of fatty acids may protect against brain toxicity induced by alpha-synuclein in Parkinson’s disease and may become a therapeutic target for these patients, a study reports.

The study, “Lipidomic Analysis of α-Synuclein Neurotoxicity Identifies Stearoyl CoA Desaturase as a Target for Parkinson Treatment,” was published in the journal Molecular Cell.

The brain is rich in lipids, or fats, which are key for neural development and nerve cell communication. Brain cells tightly regulate lipid production and uptake, as well as the distribution of its precursors, such as fatty acids. Imbalance of the brain’s lipids has been implicated in several neurodegenerative diseases, including Parkinson’s.

Alpha-synuclein, the main component of protein clumps known as Lewy bodies, interacts with fatty acids and favors their storage as triglycerides — the most common type of fat in the body — in lipid droplets in cells.

These droplets prevent the toxic effects of lipid accumulation, but may also contribute to the deposition of alpha-synuclein. Proteins related to lipid metabolism have been identified as risk factors for Parkinson’s. However, little is known about the impact of lipid metabolism on alpha-synuclein assembly and cellular alterations.

Researchers first measured lipids and fatty acid alterations in yeast that had been engineered to produce alpha-synuclein. This showed an increase in components of the neutral lipids pathway — storage lipids lacking positively and/or negatively charged groups — including a monounsaturated fatty acid called oleic acid. The team thereby hypothesized that high oleic acid levels promote the binding of alpha-synuclein to the cell membrane, increasing toxicity.

These findings were then replicated in patient cell lines, in a mouse model of familial Parkinson’s, and in a model of dopamine-producing neuron degeneration (a hallmark of Parkinson’s) in the nematode worm Caenorhabditis elegans.

“It was fascinating to see how excess [alpha-synuclein] had such consistent effects on the neutral lipid pathway across model organisms,” Ulf Dettmer, PhD, co-senior author of the study from the Brigham and Women’s Hospital and Harvard Medical School, said in a press release. “All our models clearly pointed at oleic acid as a mediator of [alpha]-synuclein toxicity.”

Researchers investigated possible ways to target fatty acids or the processes leading to their production that could protect against Parkinson’s. They found that triglycerides protect from alpha-synuclein-induced toxicity by preventing the accumulation of oleic acid and diglyceride, a type of fat composed of two fatty acid chains.

Importantly, they found that inhibiting an enzyme known as stearoyl-CoA-desaturase (SCD), which is key in the production of oleic acid, protected against cell toxicity, formation of alpha-synuclein aggregates, and a decrease in the amount of protective alpha-synuclein tetramers (natural structure formed by four subunits) relative to its aggregation-prone monomers, or single-protein chains.

“Our findings thus indicate that partial inhibition of SCD would be a rational therapeutic approach to [alpha-synuclein] neurotoxicity,” the researchers wrote.

“We’ve identified a pathway and a therapeutic target that no one has pursued before,” said Saranna Fanning, PhD, the study’s lead author.

Co-senior author Dennis Selkoe, MD, said the findings present “a unique opportunity for small-molecule therapies to inhibit the enzyme in models of [Parkinson’s] and, ultimately, in human diseases.”

The post Enzyme Linking Fatty Acids to Alpha-synuclein Could Be Parkinson’s Therapeutic Target, Study Suggests appeared first on Parkinson’s News Today.