A USF Health study applies a new mouse model of tauopathy, which may help identify therapeutic targets for Alzheimer’s and other neurodegenerative diseases

TAMPA, Fla (April 20, 2021) — Chaperone protein imbalance can play a significant role in initiating toxic accumulation of tau in the aging brain – an early step in the development of Alzheimer’s disease and related neurodegenerative disorders known as tauopathies, a new preclinical study by University of South Florida Health (USF Health) neuroscientists suggests.

Laura Blair, PhD, assistant professor of molecular medicine at the USF Health Byrd Alzheimer’s Center, was principal investigator for the NIH-funded study published in Acta Neuropathologica Communications | Photo by Allison Long, USF Health Communications

In humans, misfolding of the protein tau leads to its toxic accumulation inside brain cells, the formation of these tau aggregates into hallmark neurofibrillary tangles, neuron death, and eventually symptoms of cognitive decline such as memory loss and diminished thinking skills.

In this study the USF Health Morsani College of Medicine researchers used mice that were not genetically modified (wild-type mice) to examine the effects of Aha1 and FKBP52, two co-chaperone proteins of heat shock protein Hsp90, in the aging brain. They modeled molecular chaperone imbalance by overexpressing production of Aha1 and FKBP52 in these old, wide-type mice. The findings, highlighted below, were reported April 8 in Acta Neuropathologica Communications.

Hsp90 is a chaperone protein abundant in neurons and other cells in the brain. Normally, co-chaperone proteins assist chaperone proteins in monitoring and sustaining the balance (homeostasis) of proteins critical to cell health.

“The chaperone protein network is your cell’s natural defense to maintain homeostasis throughout life, and this study emphasizes the importance of protecting that balance in the aging brain,” said principal investigator Laura Blair, PhD, an assistant professor of molecular medicine at the USF Health Byrd Alzheimer’s Center, Morsani College of Medicine. “We’re excited about using this new model of tauopathy in finding ways to restore chaperone protein balance to delay or stop the progression of Alzheimer’s and other neurodegenerative diseases.”

Dr. Blair along with the research paper’s co-lead authors Marangelie Criado-Marrero, PhD (left), a postdoctoral fellow, and Niat Gebru (center), a doctoral student. | Photo by Allison Long

Among their many quality-control functions, chaperone protein networks ensure proteins are folded to conform to the proper 3D shapes, transported precisely where needed to do their jobs, and pushed toward degradation if they are abnormally modified or no longer useful. Heat shock proteins like Hsp90, triggered when a cell is under stress, play a particularly important “triage” role in correcting protein misfolding to prevent aggregation.

“But in the aging brain, the balance of the chaperone proteins shifts and creates a system not working as efficiently as it normally would. Large numbers of the chaperone molecules decrease in expression, and a smaller but significant number increase in their expression,” Dr. Blair said.

Increasing age is the greatest known risk factor for Alzheimer’s disease. So, the USF Health team investigated whether increased levels of FKBP52 and Aha1 alone could initiate pathological features mimicking human Alzheimer’s disease in aged wild-type mice – those with no genetic manipulations predisposing their brains to abnormally increase tau aggregation.

Tau pathology resembling that seen in Alzheimer’s disease brains. | Image courtesy of Laura Blair laboratory, USF Health

Key findings from their new mouse model of tauopathy include:

• High levels of FKBP52, and to a lesser extent elevated levels of Aha1, increased tau accumulation over time in the aged, wild-type mice.

• The tau accumulation promoted by overexpression of FKBP52, but not Aha1, correlated with increased neuroinflammation through exaggerated activation of neuronal support cells, namely microglia and astrocytes. This was complemented by loss of neurons and cognitive impairments.

Existing mouse models, including those that add or subtract genes, introduce tau mutations, and seed mice brains with human tau, help scientists learn more about the underlying causes of Alzheimer’s disease and other tauopathies. However, they tend to be limited in capturing the physiological aspects of neurodegeneration in the context of both normal and abnormal aging.

“We hope this (chaperone imbalance) model will help us better understand the dynamics of tau aggregation and neuroinflammation, including the timing and connections among pathological events, without directly regulating one pathway or the other,” Dr. Blair said.

Dr. Blair’s team has designed follow-up studies to help unravel if, and when, tau accumulation or neuroinflammation is more influential in causing brain cell toxicity during aging. That could help determine which chaperones — FKBP52, Aha1, or others — may be the best therapeutic target options for restoring protein balance, she said.

Dr. Blair’s laboratory studies how various chaperone proteins interact, for better or worse, with different forms of tau – ranging from soluble tau protein that can spread from one brain cell to another to the aggregated, misfolded neurofibrillary tangles inside brain cells.

Co-lead authors for the USF Health study were postdoctoral fellow Marangelie Criado-Marrero, PhD, and doctoral student Niat Gebru. The research was supported by grants from the National Institutes of Health/National Institute of Neurological Disorders and Stroke and the National Institute of Mental Health.

His team searches beyond the hallmark Alzheimer’s disease proteins for alternative treatments

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In his laboratory at the USF Health Byrd Alzheimer’s Center, neuroscientist David Kang, PhD, focuses on how different types of proteins damage the brain when they accumulate there. In the case of Alzheimer’s disease, decades of good science has zeroed in on amyloid and tau, as the two types of hallmark proteins driving the disease process that ultimately kills brain cells.

Dr. Kang and his team investigate molecular pathways leading to the formation large, sticky amyloid plaques between brain cells, and to the tau neurofibrillary tangles inside brain cells –including the interplay between the two proteins. But, he is quick to point out that amyloid and tau are “not the full story” in the quest to understand how normally aging brains go bad.

“Our goal is to understand as much of the entire Alzheimer’s disease process as possible and then target specific molecules that are either overactive or underactive, which is part of the drug discovery program we’re working on,” said Dr. Kang, professor of molecular medicine and director of basic research for the Byrd Alzheimer’s Center, which anchors the USF Health Neuroscience Institute.

Neuroscientist David Kang, PhD, (third from left)  stands with his team in his laboratory at the Byrd Alzheimer’s Center, which anchors the USF Health Neuroscience Institute.

Attacking dementia from different angles 

Dr. Kang’s group takes a multifaceted approach to studying the biological brain changes that impair thinking and memory in people with Alzheimer’s, the most common type of dementia, as well as Lewy body, vascular and frontotemporal dementias.

That includes examining how damaged mitochondria, the energy-producing power plants of the cell, contribute to pathology in all neurodegenerative diseases. “Sick mitochondria leak a lot of toxins that do widespread damage to neurons and other cells,” Dr. Kang said.

Dr. Kang’s team was the first to identify how mutations of a gene, called CHCHD10, which contributes to both frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), cause both mitochondrial dysfunction and protein pathology called TDP-43. Their findings on the newly identified mitochondrial link to both neurodegenerative diseases were published in Nature Communications in 2017.

The role of selective degradation in ridding cells of abnormal proteins, old or damaged organelles (including mitochondria) and other debris is another key line of research pursued by Dr. Kang and colleagues.

A single stained nerve cell | Microscopic image courtesy of Kang lab

“We believe something more fundamental is going wrong in the brain during the aging process to tip the balance toward Alzheimer’s disease – beyond what we call proteinopathy” or deposits of malformed proteins like toxic amyloid and tau, said Dr. Kang, whose work is bolstered by nearly $8 million in grant funding from the National Institutes of Health (NIH), the Veterans Administration (VA merit awards) and the Florida Department of Health.

“I think one of the fundamental things happening is that the (cellular) plumbing system isn’t working to clear out all the accumulating junk,” he said. “That’s why we’re looking at the protective clearance mechanisms (autophagy and mitophagy) that would normally quickly remove misfolded proteins and dysfunctional mitochondria.”

Unfortunately, pharmaceutical trials to date have yielded no effective treatments for Alzheimer’s disease, the sixth leading cause of death in the U.S.  Most clinical studies have centered on developing medications to block or destroy the amyloid protein plaque formation, and a few have targeted the tau-containing neurofibrillary tangles. The five Alzheimer’s drugs currently available may provide temporary relief of symptoms, such as memory loss and confusion. But, they do not prevent or delay the mind-robbing disease as toxic proteins continue to build up and dismantle the brain’s communication network.

Lesson learned: The critical importance of intervening earlier

Some scientists argue that the “amyloid hypothesis” approach is not working. Dr. Kang is among those who maintain that amyloid plays a key role in initiating the disease process that leads to brain atrophy in Alzheimer’s – but that amyloid accumulation happens very early, as much as 10 to 20 years before people experience memory problems or other signs of dementia.

Early detection and treatment are key, Dr. Kang says, because as protein plaques and other lesions continue to accumulate in the brain, reversing the damage may not be possible.

“One reason we’ve been disappointed in the clinical trials is because so far they have primarily targeted patients who are already symptomatic,” Dr. Kang said. “Over the last decade we’ve learned that by the time someone is diagnosed with early Alzheimer’s disease, or even mild cognitive impairment, the brain has degenerated a lot. And once those nerve cells are gone they do not, for the most part, regenerate… The amyloid cascade has run its course.”

As protein plaques and other lesions continue to accumulate, becoming apparent with MRI imaging, reversing the damage may not be possible.  So, for anti-amyloid therapies – or even those targeting downstream tau – to work, patients at risk of Alzheimer’s need to be identified and treated very early, Dr. Kang said.

USF Health is recruiting healthy older adults with no signs of memory problems for a few prevention trials. A pair of Generation Program studies will test the effectiveness of investigational anti-Alzheimer’s drugs on those at high genetic risk for the disease before symptoms start. And, the NIH-sponsored Preventing Alzheimer’s with Cognitive Training (PACT) study is examining whether a specific type of computerized brain training can reduce the risk of mild cognitive impairment and dementias like Alzheimer’s disease in those age 65 and older.

To accelerate early intervention initiatives, more definitive tests are needed to pinpoint biomarkers that will predict Alzheimer’s disease development in genetically susceptible people. Dr. Kang is hopeful about the prospects.  His own team investigates how exosomes, in particular the lipid vesicles that shuttle proteins and other molecules from the brain into the circulating bloodstream, might be isolated and used to detect people at risk of proteinopathy.

“I think within the next five years, some type of diagnostic blood test will be available that can accurately identify people with early Alzheimer’s brain pathology, but not yet experiencing symptoms,” he said.

Graduate research assistant Yan Yan, a member of Dr. Kang’s research team, works at a cell culture hood.

Searching for alternative treatment targets

Meanwhile, Dr. Kang’s laboratory continues searching for other treatment targets in addition to amyloid and tau — including the enzyme SSH1, which regulates the internal infrastructure of nerve cells, called the actin cytoskeleton. SSHI, also known as slingshot, is needed for amyloid activation of cofilin, a protein identified by the USF Health neuroscientists in a recent study published in Communications Biology as a possible early culprit in the tauopathy process.

“Cofilin is overactive in the brains of Alzheimer’s patients so if we can inhibit cofilin by targeting slingshot, it may lead to a promising treatment,” Dr. Kang said.

Ultimately, as with other complex chronic diseases, Alzheimer’s may not be eliminated by a single silver-bullet cure.  Rather, Dr. Kang said, a combination of approaches will likely be needed to successfully combat the neurodegenerative disorder, which afflicts 5.8 million Americans.

“I think prevention through healthy living is definitely key, because brain aging is modifiable based on things like your diet as well as physical activity and brain exercises,” he said.  “Also, we need to focus on earlier diagnosis, before people become symptomatic, and develop next-generation drugs that can attack the disease on multiple fronts.”

Xingyu Zhao, PhD, a research associate in the Department of Molecular Medicine, is among the scientists in Dr. Kang’s laboratory studying the basic biology of the aging brain.

Fascinated by how the brain works — and malfunctions

Dr. Kang came to USF Health in 2012 after nearly 20 years as a brain researcher at the University of California San Diego, where he earned M.S. and PhD degrees in neurosciences and completed NIH National Research Service Award fellowships in the neuroplasticity of aging.

As an undergraduate Dr. Kang switched from studying engineering to a dual major in science/psychology. He began focusing on neurosciences in graduate school, he said, because tackling how the brain works and malfunctions was fascinating and always challenged him.

“With every small step forward, we learn something else about the basic biology of the aging brain,” said Dr. Kang, “It’s not just helpful in discovering what therapeutic approaches may work best against Alzheimer’s disease – we’re also learning more about other neurodegenerative conditions affecting the brain.”

In addition to leading day-to-day research operations at the Byrd Center and helping to recruit new Alzheimer’s investigators, Dr. Kang holds the Mary and Louis Fleming Endowed Chair in Alzheimer’s Research and serves as a research neurobiologist at the James A. Haley Veterans Haley Veterans’ Hospital.

He has authored more than 50 peer-reviewed journal articles on brain aging and Alzheimer’s disease research. A member of the NIH Clinical Neuroscience and Neurodegeneration Study Section since 2016, he has served on multiple national and international editorial boards, scientific panels and advisory boards.

Dr. Kang sits next to a computer monitor depicting stained microscopic images — a single neuron (far left) and the two hallmark pathological proteins for Alzheimer’s disease, tau tangles (center) and amyloid plaques (right).

Some things you may not know about Dr. Kang

• His parents were Presbyterian missionaries in Africa, so he spent nine years of his early life (third through 10^th grade) in Nigeria.
• Dr. Kang practices intermittent fasting, often forgoing breakfast and eating only within an 8-hour window. Animal studies indicate the practice may contribute to lifespan and brain health by improving cellular repair through the process of autophagy, he said. “Autophagy really kicks your cells’ plumbing system into gear to clear out all the waste.”

-Video and photos by Allison Long, USF Health Communications and Marketing

The latest neuroscientist recruits will help USF Health accelerate new discoveries in Alzheimer’s disease and other neurological disorders 

The USF Health Neuroscience Institute, home of the Johnnie B. Byrd Sr., Alzheimer’s Center, brings together scientists and physicians to investigate the complexities of the brain and its impact on human health and behavior.

Internationally recognized Alzheimer’s disease researcher Gopal Thinakaran, PhD, has been recruited by USF Health to help accelerate the interdisciplinary work of its Neuroscience Institute (NSI), home of the Johnnie B. Byrd Sr., Alzheimer’s Center. Dr. Thinakaran, a professor of neurobiology at the University of Chicago, will join USF Health on Aug. 1.

University of Chicago neurophysiologist Angèle Parent, PhD, will also arrive here Aug. 1 as an associate professor of molecular medicine and member of the Byrd Alzheimer’s Center.

“Dr. Thinakaran and Dr. Parent are outstanding additions to our growing USF Health Neuroscience Institute,” said Charles J. Lockwood, MD, senior vice president of USF Health and dean of the Morsani College of Medicine. “Building upon the success of the Byrd Alzheimer’s Center, Dr. Thinakaran will help us advance interdisciplinary research among USF Health scientists and physicians looking at the brain in unique ways to accelerate discoveries to cure a broad range of neurological disorders, including Alzheimer’s and related dementias, Parkinson’s, ataxias, epilepsy, multiple sclerosis, ALS and stroke.  Moreover, Dr. Parent brings to the USF Health NSI a critical line of research into the mechanisms of memory dysfunction in dementia”

Gopal Thinakaran, PhD

Over the last decade Dr. Thinakaran built one of the country’s leading laboratories investigating the molecular and cellular processes underlying Alzheimer’s disease, the major form of dementia afflicting an estimated 5.8 million Americans.  He uses cutting-edge cell biology techniques and mouse models to probe nerve cell pathways responsible for Alzheimer’s disease pathology and neuronal dysfunction, with the goal of finding treatments to significantly reduce or delay cognitive decline.  Recently, he began exploring the molecular link between type 2 diabetes and Alzheimer’s disease progression.

Supported by $5.5 million in National Institutes of Health (NIH) grant funding, Dr. Thinakaran’s work has implications for other age-related and chronic neurodegenerative diseases that, while diverse, share some common characteristics such as abnormal protein aggregates and excessive nerve cell death.

At USF Health, Dr. Thinakaran will assume leadership roles as associate dean for neuroscience research and NSI associate director of research, in addition to his appointments as a professor of molecular medicine and the Bagnor Endowed Chair in Alzheimer’s Research. He will work closely with NSI CEO Harry van Loveren, MD; Stephen Liggett, MD, vice dean of research for the USF Health Morsani College of Medicine; and David Kang, PhD, director of basic research at the Byrd Alzheimer’s Center, to expand and integrate basic, translational and clinical neurosciences research across USF.

Dr. Parent studies how the brain remembers and what goes wrong with memory storage mechanisms in neurodegenerative diseases, focusing on communication between nerve cells (synaptic transmission) and neuronal plasticity. This April, Dr. Parent’s team published a study in Cell Reports demonstrating that sustained amyloid precursor protein (APP) signaling favors adaptive changes in the brain and prevents memory decline in an Alzheimer’s disease mouse model. She recently received a five-year, $1.75-million NIH grant to examine how differences in APP metabolism affect memory in sleep-disturbed Alzheimer’s mice.

Angèle Parent, PhD

An accomplished scientist who does not hesitate to explore uncharted territory, Dr. Thinakaran is also “a wonderful communicator, spokesman, and builder,” Dr. Liggett said. “As USF Health intensifies its effort to conquer Alzheimer’s disease and other dementias, as well as related neuroscience research, he will play an integral role in moving us forward. His combination of excellence in these skills is not that common, and I look forward to working with him to reach new heights in these research areas.”

NSI’s Dr. Van Loveren, chair of neurosurgery at MCOM, said Dr. Thinakaran recognizes the power of bringing different disciplines together to tackle the complexities of the brain and its impact on human health and behavior. “He is a scientific leader who understands the challenges of translating laboratory findings into new therapies that can target the root causes of neurodegenerative diseases – and the value of coordinated teamwork needed to bridge that gap.”

Both Dr. Thinakaran and Dr. Parent were recruited with the help of funding allocated through USF’s designation as a Preeminent State Research University.  The University of Chicago neuroscientists are the newest NIH-funded faculty members recruited since fall 2018 to strengthen and complement existing talent at the NSI’s Byrd Alzheimer’s Center. Others include:

• Krishna Bhat, MD, PhD, professor of molecular medicine and the Mary & Harry Goldsmith Endowed Chair in Alzheimer’s Disease, studies the genes and proteins that regulate the division of neuronal stem cells.
• Lianchun Wang, MD, professor of molecular pharmacology and physiology and USF Endowed Chair of Neurovascular Research, investigates the structure and function of a common linear polysaccharide, heparan sulfate, in inflammation, blood vessel development, stem cell biology, cancer and Alzheimer’s disease.
• Alexa Woo, PhD, assistant professor of molecular pharmacology and physiology, studies how multifunctional B-arrestin proteins contribute to tau pathology, a hallmark of Alzheimer’s and other neurodegenerative diseases in the brain.

Dr. Thinakaran said he was impressed by USF Health’s support of its well-established Byrd Alzheimer’s Center and the university’s drive to create an institute internationally known for its collaborative neurosciences research and training.

“I look forward to the opportunities to expand USF Health’s expertise in other neurological diseases and generate energy that will feed existing Alzheimer’s research,” he said.

New dementia drug discovery efforts get underway this month at the University of South Florida, Tampa, Fla., thanks to £875,000 funding (approximately $1.2 million) from the Dementia Consortium. The U.S. team of academics will work with drug development experts at UK-based MRC Technology, to target the immune system in a bid to halt nerve cell damage.

The investment comes as part of the £4 million Dementia Consortium – a global partnership between Alzheimer’s Research UK, MRC Technology and the pharmaceutical companies Abbvie, Astex, Eisai and Lilly. By uniting expertise, the Consortium is bridging the gap between academic research and the pharmaceutical industry in the search for new drugs to slow neurodegenerative diseases.  The Consortium’s project with the University of South Florida marks their first contract for collaboration with an American University.

The link between the immune system and neurodegeneration is the focus of intense investigation, and a number of drug discovery efforts aimed at reducing inflammation have got underway recently. In this collaborative project, Dr. David Morgan and Dr. Kevin Nash of the USF Health Byrd Alzheimer’s Institute, University of South Florida, will explore the role of immune system regulator, fractalkine, in neurodegeneration. Their previous work in animal models of Alzheimer’s disease indicated a neuroprotective role for the protein, with increased levels of fractalkine dampening inflammation, halting nerve cell death and reducing tau deposits. The team observed similar benefits in mouse models of Parkinson’s, suggesting that fractalkine receptor agonism could be a treatment approach for a number of neurodegenerative diseases.

David Morgan, PhD, CEO of the USF Health Byrd Alzheimer’s Institute and Distinguished University Health Professor (left) and Kevin Nash, PhD, assistant professor of molecular pharmacology and physiology, with an image of neurons expressing fractalkine, an immune system regulator with a neuroprotective effect.

As no known small molecule agonists of the fractalkine receptor exist, the Dementia Consortium funding will couple Dr Morgan’s expertise in neurodegeneration and in vivo validation techniques with the MRC Technology’s extensive screening capabilities and medicinal chemistry programmes.

Talking about the new funding, Dr. David Morgan, CEO of the USF Health Byrd Alzheimer’s Institute, said:

“We’ve been exploring the role of fractalkine in Alzheimer’s and Parkinson’s disease for many years now, highlighting a neuroprotective role for the protein. Thanks to funding from the Dementia Consortium, we are now able to shift our focus from pathway characterization to drug development. We’re particularly excited that this approach could have an impact across a number of different neurodegenerative diseases and look forward to coupling our disease knowledge with drug discovery experts in the UK, to help accelerate progress towards treatments.”

Dr. Simon Ridley, Director of Research at Alzheimer’s Research UK, said:

“Dementia is our greatest medical challenge, with 46 million people worldwide living with the condition. The Dementia Consortium is one of a range of initiatives by Alzheimer’s Research UK to accelerate the ‘bench to bedside’ journey, ensuring that academic insights are translated into the clinic as rapidly as possible. The high attrition rate in drug discovery means we must invest heavily in promising early stage development projects and the Dementia Consortium provides a unique vehicle for this investment, uniting expertise across the academic, technology transfer and pharmaceutical sectors.”

Close-up of microscopic image: magnified neurons expressing fractalkine.

Dr. Justin Bryans, Director, Drug Discovery at MRC Technology, said:

“Scientists are increasingly looking at the body’s own immune system to fight some of the most challenging diseases of our time. This project will progress promising findings that fractalkine could reduce inflammation and cell death. Drug discovery expertise in our laboratories will now be applied to find small molecules to stimulate the fractalkine receptor so we can move a step closer to finding a new treatment for people with dementia.”

On forming new partnerships, Valerie McDevitt, Associate Vice President for Technology Transfer & Business Partnerships at the University of South Florida, said:

“The University of South Florida places emphasis on building new relationships like this one to help bridge the gap between academic research and industry.  Our collaboration with the Dementia Consortium provides an opportunity to positively impact the treatment of neurodegenerative diseases and aligns with our university mission to serve as a highly effective major economic engine.”

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For further information, or to speak with Dr. Morgan or Dr. Ridley, please contact Emma O’Brien, Science Communications Officer at Alzheimer’s Research UK on 0300 111 5 666, mobile or email press@alzheimersresearchuk.org.