The fight against brain disease: Widow discusses Robin Williams’ death

February 11, 2017

In a compelling first-person account of beloved Bay Area comedian Robin William’s final days, his widow is spreading awareness about the dire consequences of degenerative brain diseases like the little-known Lewy body dementia.

Susan Schneider Williams visited Foster City Thursday, Feb. 9, to give a special presentation she hopes will help educate anyone who is affected by brain disease and inspire dedication to searching for a cure.

In late 2014, her husband committed suicide shortly after experiencing a rash of strange symptoms and being diagnosed with Parkinson’s disease. It wasn’t until after his autopsy it was revealed he was also suffering from an acute case of Lewy body dementia, or LBD. The discovery drove her into researching the dementia to which she now attributes her husband’s untimely death.

“Robin and I experienced this together and we experienced the symptoms. Then he left, he had to leave. And I’m here on the backside looking at it. I get the opportunity to look at the science of what he and I just experienced. So for that, I’m doing this,” Williams said. “It’s for us and for anybody who’s suffering already or who will be.”

The cause of LBD is unknown but it’s a neurodegenerative disorder that involves a mutation or buildup of a typically normal protein in the brain. Affecting 1.4 million people in the United States, it is one of the most common forms of dementia after Alzheimer’s disease and there is no cure, Williams said.

An artist and the daughter of a pathologist, Williams is channeling her experience into educating those with a loved one affected by brain disease. She also hopes to enthuse scientists and the research community to focus on finding a cure.

She’s able to traverse the discussion from purely scientific terms to sharing her own firsthand experience of watching the man she loved slip away. In September 2016, Williams wrote an essay for the Journal of the American Academy of Neurology titled “the terrorist inside my husband’s brain.”

Williams drew from the essay during Thursday’s presentation at Foster City’s Atria Senior Living titled “The Unchosen Path: Walking with Dementia.”

“The unchosen path, I certainly did not choose this, Robin didn’t choose it, no one chooses brain disease. But like so many things in life, when you gain experience by a certain journey, it’s human nature to want to pass on what you learned,” Williams said.

It began in 2013 when Robin began experiencing strange and seemingly unrelated symptoms, from a poor sense of smell to a slight tremor in his left hand. In the coming months, he was conscious of his developing more acute psychological and memory issues, she recalled.

“Alzheimer’s patients are not aware of their disintegration. This is one of the most terrifying things of LBD, especially for someone as brilliant as Robin, you are intently aware of your disintegration,” Williams said.

Looking back, she recalled how his being put on antipsychotics for a period was detrimental as people with LBD have an adverse reaction. Diagnosing these types of disease can be difficult and Robin’s situation was exacerbated by the fact he had a prior history of depression, she said. Eventually he was diagnosed with Parkinson’s, but she noted they both felt as though it was something more.

During a meeting with a neurologist, she said Robin questioned whether he had dementia or Alzheimer’s — the doctor replied no. Looking back, she wonders if her husband had been masking some of the symptoms.

Although he continued to take good care of himself, the disease was unyielding. She notes the wide array of LBD symptoms can come on sporadically, sometimes changing within minutes.

“He and I knew there had to be something bigger going on, it was just such a complex and difficult adversary. One of the hallmarks of LBD is its symptoms can come on at random and as soon as you think they’re figuring something out, it disappears and then something else pops up,” she said.

She now recounts the final months before he committed suicide in their Bay Area home Aug. 11, 2014, with the hindsight he had LBD.

An autopsy released several months later provided further explanation into the world in which his brain had deteriorated, she said.

LBD “was everywhere in Robin’s brain, it was one of the worst cases they’ve ever seen. It was in the brain stem,” Williams said. “That was the cause of death.”

Clinically, Robin had Parkinson’s but pathologically, it was LBD that took his life, she explained.

Ultimately, Williams hopes sharing her story will be a benefit to others — whether it’s a caretaker unsure of a why a loved one is struggling, or a person who may be experiencing brain disease themselves.

She cited history and how a surge of interest behind studying cancers ultimately helped find a cure for some. Now, she hopes to help galvanize momentum behind addressing the fact that 47 million people worldwide are living with dementia — a rate that’s anticipated to double in the next 20 years.

“It feels like a race, it feels like a war, and hopefully we’ll start getting cures and preventions while we still have some of these amazing people,” Williams said. “I think part of what makes these journeys so painful is that we don’t have the answers yet. And it’s just better to admit we don’t have the answers, that goes for doctors and caregivers; then we realize the disease is the enemy.”

samantha@smdailyjournal.com

(650) 344-5200 ext. 106

http://www.smdailyjournal.com/articles/lnews/2017-02-11/the-fight-against-brain-disease-widow-discusses-robin-williams-death/1776425175761.html

Stem cells: a miracle cure or playing God?

February 10, 2017

Stem cell use and research is considered by some as a morally ambiguous development for medical science.  The topic has recently been thrown into the eye of the public after Olympic Skier Chemmy Alcott decided that storing stem cells from the umbilical cord and placenta after giving birth was a worthwhile insurance plan for her potentially adrenaline-junkie baby.

In the UK, the storage of stem cells is advocated by the NHS Cord Blood Bank which asks women to donate blood from their umbilical cord and placenta after birth.  The blood stored can be used in stem cell transplants and therapies in the future. There is even a company called Cells 4 Life that enables people to store their stem cells for themselves for 25 years.  However, not every country supports stem cell research. In the European Union, five countries prohibit any research on the topic even though another seven are in full support. 

Stem cell research is thought by many doctors and medical researchers to be the cornerstone of regenerative medicine.  There are many studies into potential benefits and even cures for diseases such as Alzheimer’s, Parkinson’s, diabetes and multiple sclerosis.  However, some argue that research in this area has gone too far with regards to the use of stem cells in the reverse of aging. 

Before entering the debate on moral uses of stem cells we must understand the fundamentals.  There are multiple types of stem cell.  Embryonic stem cells can develop into a vast array of cells whereas somatic stem cells (from adults) can only differentiate into a limited variety of cells. Both are capable of duplicating indefinitely.  Scientists have however managed to make pluripotent stem cells, meaning they have taken stem cells from adults and reversed them to make them behave like embryonic stem cells. These cells are capable of replicating almost any cell in the body, and thus making the harvesting of embryonic stem cells obsolete.  This development gives an alternative to the most debateable stem cell use, that of embryonic cells. 

In 2011, the Court Justice of the European Union declared a ban on patents for research involving the destruction of human embryos, after the public became aware of the use of embryonic cells from  aborted foetuses in research concerning Parkinson’s disease.  According to Nature Science Journal, the scientists were using the dopamine (neurotransmitter) producing cells from either foetal brains or human stem cells to replace the lack of dopamine, the primary inhibitor of movement in Parkinson’s patients.  This was a breakthrough in Parkinson’s research, and although some think it should have been further developed, the use of embryonic cells is a tipping point for a number of stem cell research supporters.

Religious views on stem cell use are some of the prime inhibitors of research.  Buddhists appear to split their views the same way as the wider world; on the one hand they wish to discover new knowledge, but also do not want to do so by harming people.  According to the Conference of Catholic Bishops, there is support for ethically acceptable stem cell research.  Evidently, the idea of “ethical research” is subjective to the religion. The Southern Baptist convention is still of the opinion that it is unacceptable to destroy a human embryo for treatments as they view abortion as an act of murder, however some think that this view is ignorant of the facts of the research at the moment. It is well-known that many of the embryos used are from miscarriages, but perhaps a compromise could involve the use of those embryos.  However, in the eyes of some, that may still be considered acting as God.

This debate has not yet been settled and will not reach a conclusion for some time due to beliefs deeply rooted in religious faith.  Fortunately for researchers in this field, stem cells are considered ethically acceptable to be used.  The only real ban in regards to this research is on the use of embryonic cells as people will likely be debating, for years to come, the first moment one should be considered a person.

Image: PublicDomainPictures

• BY BRIONY PICKFORD

http://www.studentnewspaper.org/stem-cells-a-miracle-cure-or-playing-god/

Alzheimer’s May Be Linked to Defective Brain Cells Spreading Disease

NEUROSCIENCE NEWSFEBRUARY 11, 2017

Summary: Findings may help researchers better understand how diseases can spread through the brain.

Source: Rutgers.

Researchers found that while healthy neurons should be able to sort out and rid brain cells of toxic proteins and damaged cell structures without causing problems, laboratory findings indicate that it does not always occur. NeuroscienceNews.com image is for illustrative purposes only.

Rutgers study finds toxic proteins doing harm to neighboring neurons.

Rutgers scientists say neurodegenerative diseases like Alzheimer’s and Parkinson’s may be linked to defective brain cells disposing toxic proteins that make neighboring cells sick.

In a study published in Nature, Monica Driscoll, distinguished professor of molecular biology and biochemistry, School of Arts and Sciences, and her team, found that while healthy neurons should be able to sort out and rid brain cells of toxic proteins and damaged cell structures without causing problems, laboratory findings indicate that it does not always occur.

These findings, Driscoll said, could have major implications for neurological disease in humans and possibly be the way that disease can spread in the brain.

“Normally the process of throwing out this trash would be a good thing,” said Driscoll. “But we think with neurodegenerative diseases like Alzheimer’s and Parkinson’s there might be a mismanagement of this very important process that is supposed to protect neurons but, instead, is doing harm to neighbor cells.”

Driscoll said scientists have understood how the process of eliminating toxic cellular substances works internally within the cell, comparing it to a garbage disposal getting rid of waste, but they did not know how cells released the garbage externally.

“What we found out could be compared to a person collecting trash and putting it outside for garbage day,” said Driscoll. “They actively select and sort the trash from the good stuff, but if it’s not picked up, the garbage can cause real problems.”

Working with the transparent roundworm, known as the C. elegans, which are similar in molecular form, function and genetics to those of humans, Driscoll and her team discovered that the worms – which have a lifespan of about three weeks — had an external garbage removal mechanism and were disposing these toxic proteins outside the cell as well.

Iliya Melentijevic, a graduate student in Driscoll’s laboratory and the lead author of the study, realized what was occurring when he observed a bright blob forming outside of the cell in some of the worms.

“In most cases, you couldn’t see it for long but in a small number of instances, it was like a cloud that accumulated outside the neuron and just stayed there,” said Melentijevic, who spent three nights in the lab taking photos of the process viewed through a microscope every 15 minutes.

Research using roundworms has provided scientists with important information on aging, which would be difficult to conduct in people and other organisms that have long life spans.

In the newly published study, the Rutgers team found that roundworms engineered to produce human disease proteins associated with Huntington’s disease and Alzheimer’s, threw out more trash consisting of these neurodegenerative toxic materials. While neighboring cells degraded some of the material, more distant cells scavenged other portions of the diseased proteins.

“These finding are significant,” said Driscoll. The work in the little worm may open the door to much needed approaches to addressing neurodegeneration and diseases like Alzheimer’s and Parkinson’s.”

ABOUT THIS ALZHEIMER’S DISEASE RESEARCH ARTICLE

Source: Robin Lally – Rutgers 

Image Source: NeuroscienceNews.com image is adapted from Rutgers press release.

Original Research: Abstract for “C. elegans neurons jettison protein aggregates and mitochondria under neurotoxic stress” by Ilija Melentijevic, Marton L. Toth, Meghan L. Arnold, Ryan J. Guasp, Girish Harinath, Ken C. Nguyen, Daniel Taub, J. Alex Parker, Christian Neri, Christopher V. Gabel, David H. Hall & Monica Driscoll in Nature. Published online February 8 2017 doi:10.1038/nature21362

Abstract

C. elegans neurons jettison protein aggregates and mitochondria under neurotoxic stress

The toxicity of misfolded proteins and mitochondrial dysfunction are pivotal factors that promote age-associated functional neuronal decline and neurodegenerative disease. Accordingly, neurons invest considerable cellular resources in chaperones, protein degradation, autophagy and mitophagy to maintain proteostasis and mitochondrial quality. Complicating the challenges of neuroprotection, misfolded human disease proteins and mitochondria can move into neighbouring cells via unknown mechanisms, which may promote pathological spread. Here we show that adult neurons from Caenorhabditis elegans extrude large (approximately 4 μm) membrane-surrounded vesicles called exophers that can contain protein aggregates and organelles. Inhibition of chaperone expression, autophagy or the proteasome, in addition to compromising mitochondrial quality, enhances the production of exophers. Proteotoxically stressed neurons that generate exophers subsequently function better than similarly stressed neurons that did not produce exophers. The extruded exopher transits through surrounding tissue in which some contents appear degraded, but some non-degradable materials can subsequently be found in more remote cells, suggesting secondary release. Our observations suggest that exopher-genesis is a potential response to rid cells of neurotoxic components when proteostasis and organelle function are challenged. We propose that exophers are components of a conserved mechanism that constitutes a fundamental, but formerly unrecognized, branch of neuronal proteostasis and mitochondrial quality control, which, when dysfunctional or diminished with age, might actively contribute to pathogenesis in human neurodegenerative disease and brain ageing.

“C. elegans neurons jettison protein aggregates and mitochondria under neurotoxic stress” by Ilija Melentijevic, Marton L. Toth, Meghan L. Arnold, Ryan J. Guasp, Girish Harinath, Ken C. Nguyen, Daniel Taub, J. Alex Parker, Christian Neri, Christopher V. Gabel, David H. Hall & Monica Driscoll in Nature. Published online February 8 2017 doi:10.1038/nature21362

http://neurosciencenews.com/alzheimers-neurotoxic-neurons-6101/

From the community: Parkinson's Disease Patient and Family Conference Offered at Northwestern Medicine Central DuPage Hospital

February 10, 2017

Posted by Kimberly Waterman, Northwestern Medicine, Community Contributor

Northwestern Medicine Central DuPage Hospital will host a free community event featuring movement disorder specialists on the front lines of Parkinson's care. The presentation, to be held March 4 from 9 a.m.- 2:30 p.m. in the Conference Center at Central DuPage Hospital, will include discussions on medication, new treatments, nutrition and what's on the horizon for Parkinson's patients. 

Patients, families and caregivers will have the opportunity to ask questions of a multi-disciplinary team. 

Lunch will be provided. Seating is limited. To register, call 630.933.4234.

Program Schedule:

9:00 - 9:10am: Welcome: Susan Walsh, Northwestern Medicine Neurosciences

9:10 - 9:45am: The Politics of Medication, Martha McGraw, MD, and Alison Monette, BNS, MS

9:45 - 10:20am: New Treatments/What's on the Horizon, Jennifer A. Pallone, DO

10:20 - 10:40am: Break

10:40 - 11:30am: Body Language in Parkinson's Disease, Michael Mercury, PhD

11:30 - 12:30pm: Lunch

12:30 - 1:30pm: Current Controversies in Parkinson's Disease: A Panel Discussion

1:30 - 2:30pm: Gastrointestinal Issues and Nutrition, Michael Rezak, MD, PhD

The Northwestern Medicine Central DuPage Hospital Movement Disorders and Neurodegenerative Diseases Center uses an interdisciplinary team approach to provide individualized care that optimizes treatment, outcomes and experience. Care is provided by a focused and experienced team that includes specially trained neurologists, neurosurgeons, neuropsychologists, nurses, counselors and rehabilitative specialists who offer advanced treatment options and access to support and resources.

http://health.einnews.com/article/365984504/RSnyby7jSdHdo29h?lcf=Hzf-KE6h-Xmcpvzwcdl3CuzbRmZ8XaTUdg3y3lN96pg%3D

Lindquist Leaves Behind Parkinson’s Interactome as Her Parting Gift

February 11, 2017

Susan Lindquist passed away October 27, 2016.  [Courtesy of Ceal Capistrano /Whitehead Institute.]

For the many genes and proteins involved in Parkinson’s disease, it’s a small world. Basically, they are all at least friends of friends. Leveraging connections between yeast genes to infer links between human genes, researchers led by the late and beloved Susan Lindquist of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, have just made that clear. Capping Lindquist’s research focus of the past five years of her life, her associates in academia and biotech have generated an extensive interaction map of genetic players in various synucleinopathies using TransposeNet, a computational algorithm they devised to “humanize” the yeast interactome. This bird’s-eye view, published January 25 in Cell Systems, revealed links between multiple parkinsonian risk factors and biological processes already projected to drive the disease. In particular, the map highlighted the importance of vesicular trafficking as well as mRNA processing and translation in α-synuclein toxicity. In a companion study from Lindquist’s lab, the researchers added a spatial dimension to these genetic connections by uncovering more than 200 proteins that brush shoulders with α-synuclein in the cell. They hope that TransposeNet and the physical interaction methods they developed can be used to identify other disease-relevant interactomes.

“This duet of papers represents the swan song of one of the deepest thinkers into the fundamental biology of neurodegeneration, our recently departed friend Sue Lindquist, who sadly died a few months ago,” commented Gregory Petsko of Weill Cornell Medical College and Scott Small of Columbia University in New York, in a joint comment to Alzforum. “The papers illustrate the magnificent creativeness and scope of her life’s work, integrating yeast, genomic, and computational biology with symphonic elegance.” Lindquist succumbed to cancer at age 67 (see New York Times obituary). 

“This body of work meant a good deal to Susan, because it provided a glimpse of how basic questions she had worked on for decades might play out one day to make a difference in the clinic,” former Whitehead researchers and co-authors on the current papers Vikram Khurana, Chee Yeun Chung, and Daniel Tardiff wrote in an accompanying tribute to their late mentor. “A basic biologist to the core, Susan was also a deeply engaged and empathic human being. It is thus not surprising that driving basic biological insights for the betterment of patients and humanity became an all-consuming goal for her in the latter part of her career.” 

From Yeast to Human. 

Yeast screens pinpoint genes involved in α-synuclein toxicity; after that, intermeshed yeast and human interaction maps display how disease processes connect.  [Courtesy of Khurana et al., Cell Systems, 2017.]

The comprehensive interaction maps may provide a biological framework in which to place rare genetic variants discovered in patients, said Khurana, the first and co-corresponding author, who now heads a lab at Brigham and Women’s Hospital, Boston. A greater understanding of how different genetic lesions relate to mechanisms that drive the disease may then pave the way for personalized therapies, he added.

Parkinson’s disease (PD) is the most common synucleinopathy; however, aggregates of α-synuclein crop up in a slew of disorders featuring parkinsonian symptoms, including dementia with Lewy bodies and multiple system atrophy, and indeed many cases of Alzheimer’s. While mutations or multiplications of the α-synuclein gene by itself cause α-synuclein pathology and PD, many other genetic culprits—both common and rare—have been identified that either cause or raise the risk of PD-like disorders, some unrelated to α-synuclein pathology (see Jul 2014 news). Understanding the connections between these diverse genetic factors and how they relate to α-synuclein aggregation will be key to finding effective treatments, Khurana said.

Genome-wide screens are a powerful way to find factors that enhance or suppress α-synuclein toxicity, and the humble yeast, with its supreme genetic malleability, offers a ready system in which to conduct these screens. Lindquist spearheaded this approach long ago, implicating protein trafficking as a driver of toxicity (see Dec 2003 news). Since then, Lindquist’s and other labs have used the screens to pin genetic modifiers of Aβ, TDP-43, and α-synuclein toxicity (see Oct 2011 news on Treusch et al., 2011; Apr 2008 news; Yeger-Lotem et al., 2009). Next, the researchers used the yeast genetic windfall to explore the roles of these genes in human disease and uncover other genes that may be involved (see Oct 2013 news; Dec 2013 news; Mar 2014 conference news; Aug 2010 news). Alas, relying on yeast to understand neurodegeneration has its limitations. Besides the obvious—yeast have no brains—there is the fact that there are no yeast homologs for human PD genes such as α-synuclein and LRRK2.

Bridging the Gap

In the current study, co-first authors Khurana, Jian Peng, now at the University of Illinois in Urbana-Champaign, and Chung, now at Yumanity Therapeutics in Cambridge, sought to flesh out the information they gathered from yeast screens and unearth the genes’ deeper context in humans. First, they expanded the screening in yeast. Previously, the researchers had overexpressed each gene of the yeast genome in yeast cells expressing α-synuclein, and uncovered 77 modifiers of α-synuclein toxicity. This time, they added a deletion screen, to identify genes that normally suppress α-synuclein toxicity, and a “pooled” overexpression screen, to test various genes simultaneously. Pooling makes screening more efficient so subtle modifiers can be detected, too. Together, these screens yielded 332 genes that either suppressed or enhanced α-synuclein toxicity in yeast. 

To “humanize” this list, the researchers teamed up with computational biologists Peng and co-corresponding authors Bonnie Berger of the Harvard Stem Cell Institute, and Ernest Fraenkel of Massachusetts Institute of Technology to develop TransposeNet. To find human homologs of a given yeast gene, the algorithm relied on sequence and structural similarities, and also on similarities in known interaction partners. Applying TransposeNet to the whole yeast proteome assigned 4,923 yeast proteins to human homologs, and conversely predicted yeast homologs for 15,200 human proteins. The researchers used this rubric to convert their 332 yeast proteins into human homologs, then generated an interaction network between those.

 Finally, because far fewer connections between human proteins are known compared to the wealth of available yeast interaction data, the researchers used the yeast proteome to fill in missing connections in the sparse human one. “It’s like giving the human proteome a yeast roadmap,” Khurana told Alzforum. The network approach allowed the researchers to visualize connections not just among their original screen hits, but between human proteins that might have no yeast homolog.

Functional Cliques. These color-coded biological processes influence the toxicity of α-synuclein. [Courtesy of Khurana et al., Cell Systems 2017.]

Lo and behold, the resulting genome-scale map of α-synuclein toxicity modifiers included several genes previously implicated in PD and other neurodegenerative diseases. Vesicular trafficking stood out as the most prominent biological process in the network, and several genes associated with typical PD, such as α-synuclein, LRRK2, and VPS35, were connected within these vesicle trafficking hubs. Proteins involved in ER-to-Golgi trafficking and ER quality control connected the two best-known PD genes, LRRK2 and α-synuclein. Importantly, neither of these genes popped up in the network without incorporating the yeast interactome to bolster the human one. 

Other key members of this endosomal trafficking clique included the yeast homologs of these human genes:

RAB7L1, an endosomal trafficking gene and leading candidate for the PARK16 locus;

VPS35, aka PARK17, a member of the retromer complex and a causal PD gene;

SYNJ1, aka PARK20, which also plays a role in Golgi-to-endosome trafficking;

SORL1, an AD risk factor.

Deleting any of these genes in yeast that express normal, otherwise non-toxic levels of α-synuclein triggered growth defects. VPS35 harboring the PD-causing mutation D620N was unable to rescue deletion of the wild-type gene. Together, these findings provided support for the biological significance of endosomal trafficking, specifically retrograde transport, in PD and related disorders. 

Calcium signaling genes, including calcineurin and NFAT, made an appearance smack dab in the heart of the interaction map, forming connections with several disparate biological processes. For example, calcineurin interacted with vesicular transport proteins as well as ATP13A2, aka PARK9, which encodes a type 5 ATPase implicated in metal ion homeostasis. Mutations in ATP13A2 cause a rare juvenile form of parkinsonism called Kufor-Rakeb syndrome, and the researchers found that deleting this gene in yeast boosted α-synuclein toxicity while overexpression suppressed toxicity. Interestingly, only three of 77 genes that modified toxicity in α-synuclein overexpressing cells altered toxicity in ATP13A2 deletion strains, as well. All three genes play roles in iron and manganese homeostasis, which are disrupted in Kufor-Rakeb syndrome. This supports the idea that metal ion transport represents a distinct biological pathway to α-synuclein toxicity, and perhaps to different forms of PD. Yet another set of 69 genes modified toxicity in VPS35 deletion strains as well as in α-synuclein overexpressors, indicating that vesicular trafficking plays a different, and perhaps more important role in typical forms of PD.

That mRNA translation and processing emerged as central to α-synuclein toxicity was the most intriguing outcome from the screens, according to Khurana. The requisite genes include the translation initiation factors EIF4G, whose role in PD is disputed, and ATNX2, implicated in ataxia as well as ALS risk, and several ribosomal subunits. In further support of this, the researchers found defective protein synthesis in HEK cells overexpressing α-synuclein and in iPSC-derived neurons harboring α-synuclein with the A53T mutation. These translation problems occurred before the canonical ER stress response had a chance to kick in, Khurana said. Overexpressing EIF4G1 or ATXN2 reversed these protein translation defects. The researchers hypothesize that the involvement of so many factors related to mRNA processing and translation implies a deep biological connection between α-synuclein and these processes.

Touched by α-Synuclein

In their second paper, Chung and Khurana, as co-first and corresponding author, prbrvided support for these and other associations discovered in the genetic study. Using a technique called ascorbate peroxidase (APEX) labeling, which was developed by Alice Ting and colleagues at Massachusetts Institute of Technology, the researchers identified 225 proteins in close physical proximity to α-synuclein in neurons. Older methods such as co-immunoprecipitation require lysing of the cell and tend to identify only stable protein complexes; in contrast, APEX identifies even transient protein-protein interactions while the cells still live. The researchers employed the technique by fusing α-synuclein with APEX, which oxidizes phenol derivatives to phenol radicals. These extremely short-lived radicals then covalently react with amino acids in their immediate vicinity, allowing identification of labeled proteins by mass spectrometry. 

Chung and colleagues transduced rat primary cortical neurons with α-synuclein fused to APEX2, a catalytically superior version of APEX, and then ran mass spec to unveil α-synuclein’s social network. Many of the 225 proteins the researchers uncovered hailed from α-synuclein’s known stomping grounds of vesicles and synaptic terminals. Biological processes that had been well represented in the genetic networks, such as protein transport and vesicular trafficking, once again made a showing in the APEX assay. In addition, microtubule-associated proteins, including tau, rubbed shoulders with α-synuclein, as did proteins involved with mRNA binding, processing, and translation.

Khurana was particularly intrigued by this last group of interactions. “Synuclein is physically and genetically interacting with translation and mRNA metabolism factors in a way that is surprising and distinct from other neurodegenerative disease proteins,” he told Alzforum. “The two papers together would suggest that there may be a physiological role for α-synuclein in mRNA metabolism that was not previously appreciated.” He speculated that perhaps α-synuclein physically associates with translation factors and sequesters them. This could occur in the synapse, where synuclein concentrates and local mRNA translation plays a key role in synaptic plasticity.

Mark Cookson of the National Institutes of Health in Bethesda, Maryland, was not surprised that translation appears important in α-synuclein toxicity. He noted two recent studies implicating the PD genes PINK, Parkin, and LRRK2 in mRNA translation (see Gehrke et al., 2015; Apr 2014 news). Still, Cookson favors the idea that α-synuclein and translation are most strongly linked via malfunctions in vesicle trafficking, which halt translation.

Because the APEX2 map was generated in neurons, it captured neuronal-specific interactions that the humanized yeast genetic screens missed. The spatial map featured multiple neuron-specific RAB3 proteins involved in synaptic vesicle exocytosis. Previous studies had implicated these proteins as modifiers of α-synuclein toxicity in neurons (see Gitler et al., 2008; Chung et al., 2009). The researchers went on to confirm many of the physical interactions identified in the APEX2 screen using a technique called membrane yeast two-hybrid. MYTH is a spin-off of classical yeast two-hybrid methods; it works well for α-synuclein, which is primarily a membrane-associated protein.

Khurana thinks it is reassuring that a number of the genes and proteins had known ties to PD. “Visualizing how they fit together is important and makes one wonder how many of the other genes in our network are related to PD risk,” Khurana said. Two of the genes in the network, calcineurin and Nedd4, are targets of available drugs that reduced α-synuclein pathology in mouse models, and he suggested the network approach might one day lead to the development of therapies aimed at mechanisms driving specific forms of disease (see Oct 2013 news and Aug 2014 news). Cookson especially welcomed the integration of parkinsonism genes into the APEX2 network. Should treatments beyond dopaminergic therapies pan out someday, it could help steer patients toward therapies specifically tailored to address the biological mechanisms that underlie their disease, he said. On the flip side, the networks also point out that patients with different clinical presentations may share common mechanisms of disease, such as defects in vesicular trafficking, he added.

In their tribute to Lindquist, Khurana, Chung, and Tardiff wrote that they believe in the potential of yeast-to-human approaches, but were careful not to tout them too heavily until they yield effective therapies. The three researchers co-founded Yumanity Therapeutics with Lindquist to translate findings in yeast and human neurons into therapies for neurodegenerative disease. “We continue to fight the good fight, spurred on by memories of a transformative woman and the uncommonly beautiful biology she brought back from a billion years ago,” they wrote.—Jessica Shugart

http://www.alzforum.org/news/research-news/lindquist-leaves-behind-parkinsons-interactome-her-parting-gift

Mitochondrial lipids as potential targets in early onset Parkinson's disease

February 10, 2017

Patrik Verstreken (VIB-KU Leuven)

A team of researchers led by Patrik Verstreken (VIB–KU Leuven) have identified an underlying mechanism in early onset Parkinson's. Using flies, mice and patient cells, the team focused on cardiolipin, a fat unique to cells' mitochondria, organelles that produce energy. They demonstrated that reducing the effects of the protein FASN influences the mitochondria, leading to increased cardiolipin levels and reduced Parkinson's symptoms. These results could pave the way to therapies for Parkinson's disease that target lipids. The team's research was published in the scientific magazine Journal of Cell Biology.

An estimated 10 million people are currently affected by Parkinson's disease worldwide. A small percentage gets confronted with the disease before the age of 40. While the affection's causes are not yet known, scientists believe that they consist of both genetic and environmental factors. In genetic Parkinson's disease, a mutation in the PINK1 gene causes changes in neurons' mitochondria, leading to the degeneration of these neurons.

Existing oncological applications

In this study, prof. Verstreken and his team, consisting of collaborators in Belgium, Germany and Portugal, observed that a protein responsible for lipid creation in cells, FASN, bypasses the genetic defect in mitochondria.

Prof. Patrik Verstreken (VIB–KU Leuven): "Several drugs that block FASN already exist, as this protein is also important to cancer research and treatment. Many of them have already been used in clinical trials. Thanks to this research, we can now test them in the context of Parkinson's disease."

Unexpected effects of FASN protein

In the course of their research, the researchers encountered a surprising observation. Using fly, mouse and human cell models, they saw that FASN has a direct effect on mitochondria, which have their own separate genomes and operate as energy producing entities within their cells.

Prof. Patrik Verstreken (VIB–KU Leuven): "The PINK1 gene encodes the PINK1 protein, and mutations in it lead to lower levels of cardiolipin in mitochondria. It was unexpected to see that blocking FASN – which is not localized to the mitochondria – actually sidesteps the mitochondrial effects of the PINK1 mutation. As a result, blocking FASN increases the amounts of a specific type of lipids in mitochondria, reducing the degradation of neurons."

Translating insights into therapies

Prof. Verstreken has already identified several targets for future research projects seeking greater insights into the link between the amounts of specific lipids in neurons and Parkinson's disease.

Prof. Patrik Verstreken (VIB–KU Leuven): "Some questions need to be answered before new therapies can be developed, such as 'is there a link between early onset Parkinson's prevalence and progression with lipid content?' And while we successfully demonstrated that cardiolipin can improve the function of mitochondria in flies, mouse models and in human cells, we need to explore its effects in actual patients."

More information: Melissa Vos et al. Cardiolipin promotes electron transport between ubiquinone and complex I to rescuedeficiency, The Journal of Cell Biology (2017). DOI: 10.1083/jcb.201511044

Journal reference: Journal of Cell Biology

Provided by: VIB (the Flanders Institute for Biotechnology)

https://medicalxpress.com/news/2017-02-mitochondrial-lipids-potential-early-onset.html

Peroxisomes—the hybrid organelle

February 10, 2017

Like the human body itself, cells have structures within them that perform special tasks. These cellular structures are called organelles, and discovering more about organelles is key to unlocking the reasons why certain cells misbehave, causing diseases such as Parkinson's, for example.

In a paper published in Nature on Feb. 1, 2017, a team of researchers from the Montreal Neurological Institute and Hospital of McGill University: Ayumu Sugiura, Sevan Mattie, Julien Prudent, and Heidi M. McBride, examined the origins of organelles called peroxisomes. They found that this very important organelle has two origins, which is unique in the field of cellular biology.

We spoke with Heidi McBride, the senior author of the study, to learn more about this discovery:

What are peroxisomes?

Peroxisomes are small, membrane bound organelles inside of every cell. They get their name because they neutralize cellular peroxide, which is very toxic, into water. This study looked at how peroxisomes may be born in mammalian cells - including humans. We made a surprising discovery: new peroxisomes are formed as a hybrid organelle. That means they come from two distinct sources, in this case the organelles endoplamic reticulum and mitochondria.

Is it unusual for an organelle to have a hybrid nature like this?

Yes! It is really the first example of such a hybrid organelle within cell biology. Only the mitochondria and peroxisomes were known to be isolated, self-sufficient organelles able to grow and divide on their own. These two organelles have always been unique in that way. Mitochondria have their own DNA that is a remnant from their early origins as an alpha-proteobacteria, and mitochondria still retain much of their autonomy. Peroxisomes have been more complicated to figure out, but it was generally accepted that in addition to their autonomous growth and division, that they could sometimes be generated as a sub-domain of the endoplasmic reticulum. Our works leads to a complete re-evaluation of this model.

Do they do anything else besides break down peroxide?

In addition to enzymes that neutralize peroxide, they also have essential roles in breaking down complex fatty acids. Many human diseases are a result of mutations in this pathway, where there is an accumulation of very long chain and branched fatty acids, for example in X-linked adrenoleukodystrophy. But peroxisomes also have specific functions in different tissues, for example in the liver they house enzymes that make bile, which is transported into the gut to break down food. In the brain they are critical to make a specific protective lipid called plasmalogen, which makes up nearly 70 per cent of the myelin sheets that wrap around neurons. So these are very important organelles that are largely unstudied in the context of disease.Myelin … that makes me think of MS, where the myelin sheath around neurons is damaged. Could there be a link between peroxisome development and MS?

It is not clear how peroxisomal dysfunction may contribute to neurodegenerative disease, particularly in multiple sclerosis where the myelin is lost and axons become exposed. We are now looking at how peroxisomes behave in models of MS, and whether or not increasing their numbers may help combat the toxicity and work towards rebuilding the myelin sheets. This work provides a new framework to look at peroxisomal formation and growth, allowing us to move into more complex systems that are very relevant to disease.

Are there any diseases where peroxisomes are already known to play a role?

Yes. There are many rare diseases where peroxisomes cannot form, or cannot perform their function. For example, a condition called Zellweger syndrome results in patients either completely lacking peroxisomes, or with peroxisomes that remain "empty" and without function. These patients are extremely ill, as they cannot make myelin, nor bile, and they accumulate many toxic metabolites from peroxide to fatty acids. The lifespan of these patients is only a few months to about two years. There is currently no treatment for these patients, so learning how we may trigger new peroxisomal biogenesis could be important to develop new strategies for therapy.

What role do mitochondria play in the formation of peroxisomes?

Mitochondria are well known as the "energy powerhouse of the cell", using the oxygen that we breathe to convert glucose and fat into cellular energy. However, mitochondria do a great deal more than this. Like peroxisomes, they perform many additional biochemical tasks. Some of these tasks are shared with peroxisomes, particularly the breakdown of fatty acids, but also in the generation of bile in liver and plasmalogen in the brain. Both organelles also play important roles in neutralizing toxic chemicals. However, mitochondria had not been implicated in the formation of new peroxisomes until our study. We found that in skin cells from Zellweger patients lacking peroxisomes, that some peroxisomal proteins are inserted into the mitochondria, while others targeted the endoplasmic reticulum. These proteins are then packaged into small membrane vesicles that are ejected from each organelle. When they fuse together, the proteins that had been separated within distinct organelles now come together and assemble into a larger protein complex that act like a gate allowing entry of a host of peroxisomal proteins and enzymes into the newly born peroxisome. We saw this occur also in normal, healthy cells where the number of peroxisomes was greatly reduced, suggesting that there is some kind of sensing mechanism that "knows" when to make peroxisomes from scratch, and when to just let them grow and divide from pre-existing peroxisomes. How this sensing system works in the brain or other organs is a major question for our future work.

What implications does this have for future research?

We hope that this work may shine new light on this essential and understudied organelle. Mitochondrial dysfunction has been increasingly linked to many disease states, including Parkinson's, MS, Alzheimers, cancer and many others. Given the close links between mitochondria and peroxisomes, we wonder how dysfunctional mitochondria may impact peroxisomal activity and biogenesis, and how this may contribute to the worsening of disease. There are many new questions raised, as we must now gain a better understanding of the mechanisms and signals that initiate the formation of newly born peroxisomes, and their contribution to both rare and common disease. We believe this work will have a great impact on the field of peroxisomal biology, and in time, we will understand the impact on human disease progression.

More information: Ayumu Sugiura et al. Newly born peroxisomes are a hybrid of mitochondrial and ER-derived pre-peroxisomes, Nature (2017). DOI: 10.1038/nature21375 

Journal reference: Nature

Provided by: McGill University

https://medicalxpress.com/news/2017-02-peroxisomesthe-hybrid-organelle.html