Every brain affected by Alzheimer’s disease carries two telltale signs: sticky clumps of a protein fragment called amyloid-beta, and tangled threads of another protein called tau. Scientists have studied both for decades. Yet a comprehensive new paper, published in the journal Cell Death & Disease, makes one thing clear: we still don’t fully understand how these two proteins cause the damage that leads to memory loss and cognitive decline.
This matters for anyone touched by Alzheimer’s disease. Understanding what researchers know — and don’t know yet — helps explain both the promise and the limits of current treatments.
What this paper covers
It’s important to know what kind of paper this is before digging into what it says. This is a review article, meaning the authors combed through and synthesized findings from many separate studies — mostly experiments in mice and cells, plus a few observations in human brain tissue and clinical trials. That means the paper’s strength lies in connecting the dots across a large body of work. Where the underlying studies disagree or fall short, the review says so.
The review is comprehensive and written for scientists, delving into the brain’s intricate workings and the interplay among cells and molecules. We put together a simplified version of this important paper so that everyone could better understand how amyloid and tau function and how they contribute to the development of Alzheimer’s disease.
The two culprits, explained simply
Amyloid-beta starts as a normal protein sitting in brain cell membranes. Enzymes cut it into fragments. Under healthy conditions, this process causes no harm. But researchers believe that under Alzheimer’s disease, something goes wrong — either too much amyloid-beta gets produced, or the brain fails to clear it away. The fragments clump together, first into small clusters called oligomers, then into larger, insoluble plaques that accumulate between brain cells.
The oligomers are among the most toxic forms of amyloid. They interfere with brain cell signaling and even weaken support cells called astrocytes that normally clean up cellular debris, including amyloid-beta itself. That creates a vicious cycle: less cleanup means more amyloid buildup, which further reduces cleanup capacity.
Tau works differently. In healthy brain cells, tau acts like scaffolding, holding the internal skeleton together with “microtubules” that transport nutrients and signals. In Alzheimer’s disease, tau becomes chemically altered — a process called hyperphosphorylation — and loses its scaffolding role. Loose tau clumps together into tangled fibers called neurofibrillary tangles. These tau tangles disrupt the transport system inside brain cells and appear to spread from one brain cell to the next, gradually recruiting more of the brain into the disease process.
Notably, the review highlights growing evidence that tau tangles may do even more damage to brain circuits than amyloid plaques — a shift from the traditional view that treated amyloid as the primary driver and tau as a secondary bystander.
Amyloid and tau work together — and that’s the real story
Perhaps the most important message from this review is that amyloid-beta and tau don’t act alone. Mouse studies described in the paper show that when both proteins are present together, brain cell activity drops much more than when either protein is present alone. In other words, the combination appears to be worse than the sum of its parts.
Researchers have also found signs that amyloid and tau interact in certain brain regions, particularly areas involved in memory. One brain-imaging study identified two patterns of interaction: a “remote” pattern, in which amyloid-affected and tau-affected brain cells damage each other at a distance through their connections, and a “local” pattern, in which the two proteins interact more directly. Both patterns seem to accelerate tau’s spread through the brain.
What researchers still don’t know about Alzhiemer’s
The review is candid about the magnitude of the remaining knowledge gaps. The authors repeatedly note that key mechanisms in the malfunctioning of amyloid and tau remain unknown. A few examples stand out:
- Why do brain cells start making too much amyloid or tau in the first place? The triggers — genetic, environmental, or otherwise — remain poorly defined for most Alzheimer’s patients.
- How exactly does tau spread between brain cells? Researchers suspect it travels within tiny cellular packages called exosomes, but the exact mechanism hasn’t been confirmed.
- Why do some people resist the damage? A small group of people show textbook Alzheimer’s-related changes in their brain tissue after death, yet never developed memory problems while alive. Studying their brain cells has revealed unique molecular and genetic pathways that appear to protect connections between brain cells from amyloid-related damage. If scientists can pin down how that resistance works, it could point toward entirely new treatment strategies.
- How does diet play a causal role? One mouse study found that a high-salt diet promoted tau buildup and memory problems, tied to reduced blood vessel function in the brain. While we don’t know whether the same condition occurs in people, it suggests that vascular health and brain protein buildup may be more closely connected than once thought.
Treatment and prevention of Alzheimer’s disease
Immunotherapy to reduce amyloid and tau
The review also points out that no current treatment reverses Alzheimer’s disease. This is in no small part due to the complicated physiology of Alzheimer’s disease. Existing options manage symptoms, and recently approved anti-amyloid treatments modify disease progression.
Immunotherapy — vaccines and antibodies that train the immune system to clear amyloid or tau — is highlighted as one of the more promising avenues for treatment. Recent clinical trials of both anti-tau and anti-amyloid vaccines showed some evidence for improvement and support the conduct of larger trials.
Early detection and prevention
The lead author of the review paper is Dr. Domenico Praticò, an Alzheimer’s expert and Professor at the Lewis Katz School of Medicine at Temple University. While we still have much to learn about Alzheimer’s disease, Dr. Praticò finds many reasons to be optimistic. The key may be to stop the disease before it causes symptoms. He notes that early detection with new blood biomarkers and imaging is accurate and consistent. This allows for personalized treatment and early prevention. For example, addressing modifiable risk factors like diabetes, overweight, diet, and inactivity can greatly reduce the chance of developing dementia and Alzheimer’s.
“The research landscape of Alzheimer’s disease has changed; the future is at hand. A future when early diagnosis is going to be a routine process. A time when we could know a decade or two in advance if an individual will develop Alzheimer’s disease or other forms of dementia. A future when we can immediately and proactively intervene with therapies and other strategies targeting modifiable risk factors.”
— Domenico Praticò, MD
Founding Director and Professor,
Alzheimer’s Center at the Lewis Katz School of Medicine,
Temple University
The bottom line: our current understanding of amyloid and tau
Alzheimer’s disease results from a complex partnership between two misbehaving proteins, amyloid-beta and tau, that reinforce each other’s damage to brain cells and their connections. Scientists have made real progress mapping how each protein misfolds, spreads, and harms neurons. But large gaps remain — particularly around what triggers the disease process in the first place, and why a few people seem naturally protected against it.
That combination — real progress alongside real uncertainty — is what makes this an active and urgent area of research, not a solved problem. Continued investment in understanding the basic biology, not just symptom management, is what the researchers behind this review argue will be needed to develop treatments that meaningfully change the course of Alzheimer’s disease.
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