In people with Alzheimer’s disease and other forms of dementia, certain proteins in an otherwise healthy brain stop working the way they should. One of these proteins is called tau. Scientists now believe that tau plays a major role in how Alzheimer’s disease develops and gets worse over time.

In this article, we’ll explain what tau protein is, how it normally works in the brain, and what happens when it doesn’t work properly. You’ll also learn how tau affects learning, memory, thinking, and neuron (brain cell) health. While tau is just one part of the story, it may hold some of the biggest clues to understanding and treating Alzheimer’s in the future.

What Is Tau Protein?

Tau is a protein found mostly in neurons — the nerve cells of the human brain and nervous system. In a healthy brain, tau helps keep the tiny internal “skeleton” of the neuron strong. Each neuron has long, tubelike structures called microtubules. These act like train tracks within the cell. Microtubules carry nutrients and other materials from the cell body, down the axon (a long fiber that sends signals), to the dendrites (branchlike parts that receive signals).

Tau helps keep tiny tracks in brain cells stable so the cells can move nutrients and signals where they need to go. It also helps the neuron keep its shape, which is important for sending signals. Tau makes sure signals can travel through the cell and across the synapse — the small gap between neurons where messages are passed. In healthy brains, tau is flexible and dissolves easily in fluid.

Tau comes in different forms that are found in the brain. These forms of tau usually help healthy brain cells work properly. Overall, the main role of tau is to support neurons by keeping their internal transport system working. This system is important for memory, thinking, and other brain functions.

How Tau Is Involved in Alzheimer’s Disease and Other Forms of Dementia

In Alzheimer’s disease, tau doesn’t work the way it should. Changes occur that cause tau to become misfolded and sticky. This happens partly because of a process called hyperphosphorylation, which is when too many phosphate molecules attach to tau and weigh it down. This weight causes tau to lose its grip on the microtubule tracks and float free. The tau proteins then start clumping together with each other. At first, they form small clusters called oligomers.

As the problem gets worse, oligomers turn into twisted clumps called tau tangles or neurofibrillary tangles. These tangles prevent neurons from moving important nutrients and sending signals. Over time, the buildup of tau tangles causes neurons to get sick and die.

A recent study found that tau tangles are strongly linked to cognitive decline (thinking problems). Researchers found that the number of tau tangles in the brain was more closely associated with memory loss and cell signaling problems than the number of amyloid plaques. Amyloid plaques are clumps of sticky amyloid-beta protein that build up outside of brain cells. They’re another key feature of Alzheimer’s disease.

Tau problems don’t just happen in Alzheimer’s disease. They’re also seen in other neurodegenerative diseases called tauopathies. Some of these include:

• Frontotemporal dementia (FTD)
• Progressive supranuclear palsy (PSP)
• Pick’s disease

In FTD, for example, tau tangles damage the frontal and temporal lobes of the brain. These areas control language, behavior, and personality. This is different from Alzheimer’s, which often starts with memory problems. In PSP, tau affects parts of the brain that control movement and balance.

Scientists now know that tau can spread from one neuron to another. One study showed that tau uses special receptors (proteins that receive signals) to move around. This may explain why Alzheimer’s disease and other tauopathies get worse over time.

No matter the specific disease, once tau becomes abnormal, it can cause more problems over time. These issues may include memory loss, confusion, trouble with movement, and other serious symptoms. The slow spread of abnormal tau shows how deeply these diseases can impact people and their families, affecting every part of their lives.

How Tau Affects Memory and Thinking

When abnormal tau builds up in the hippocampus (the brain area that controls memory), it results in memory loss. This region is important for forming and recalling memories. As neurons in this area get sick from tau buildup and die, a person may start forgetting recent events and struggle to learn new information. This is why short-term memory loss is often an early sign of Alzheimer’s disease.

As tau spreads to other brain regions, other cognitive functions are affected. For example, if tau grows to the frontal lobes, someone may have trouble with planning, judgment, or behavior. If the tangles spread to areas responsible for language, the person may have difficulty finding the right words. In later stages of the disease, widespread damage from tau can lead to severe cognitive impairment. Even basic tasks and recognizing loved ones may become difficult.

Tau Protein vs. Amyloid Plaques in Alzheimer’s

Both tau tangles and amyloid plaques are hallmarks of Alzheimer’s disease. However, they have different roles and show up in different places. Amyloid-beta (the protein that forms amyloid plaques) builds up outside of neurons, forming sticky plaques between cells. Tau, on the other hand, builds up inside neurons as neurofibrillary tangles.

Amyloid plaques often show up early, sometimes years before symptoms begin. Tau tends to show up later, closer to when memory and thinking problems start. Scientists think that amyloid plaques may trigger the disease, leading to a chain of events that leads to abnormal tau. Some studies are exploring whether removing amyloid first can slow down tau pathology (development of abnormal tau).

New Biomarkers and Treatments That Target Tau

In the past, doctors could only confirm the amount of tau tangles in brain tissue after someone’s death (known as a postmortem autopsy). Today, new biomarkers — signs of disease in the body — can help doctors find tau changes in people while they’re still alive. For example, scientists can measure these changes using a sample of cerebrospinal fluid — the clear fluid around the brain and spinal cord.

Neuroscience researchers have also developed blood tests that can detect abnormal forms of tau. A 2024 study showed that a blood test for a specific piece of tau protein (called p-tau217) could identify Alzheimer’s disease years before symptoms begin.

Beyond diagnosis, a major focus in neuroscience research is developing treatments designed to target tau. Many clinical trials are already underway. One approach is by using monoclonal antibodies (lab-made immune proteins) that bind tau. These antibodies act like magnets. They attach to tau, marking it for removal by the immune system, or blocking its ability to spread. So far, the U.S. Food and Drug Administration (FDA) has only approved monoclonal antibody treatments that target amyloid, not tau. However, researchers are hopeful that they can successfully be made for tau treatment soon, too.

In a recent study by researchers at the University of Pennsylvania, scientists found that a certain gene, called TRIM11, may help stop tau from forming dangerous tangles. In mouse models of Alzheimer’s, adding TRIM11 helped remove tau clumps and improved memory and movement. Researchers hope that boosting TRIM11 in the brain could someday become a new way to treat tauopathies.

Hope for the Future

While there’s no cure for Alzheimer’s disease yet, researchers are making meaningful progress every day. Scientists are learning more about how tau contributes to memory loss and cognitive decline. New treatments are being tested in clinical trials, with the goal of slowing or even reversing the disease.

If you or a loved one is living with Alzheimer’s disease, talk with a neurologist or a member of your healthcare team. They can share the latest information about treatments and research studies. Some people may qualify for clinical trials that offer access to new therapies before they’re widely available. You can find these online at ClinicalTrials.gov by searching “Alzheimer’s disease” and entering your location.

Remember, managing Alzheimer’s takes a team — including neurologists, primary care doctors, therapists, social workers, and support groups — all working together to provide the best care possible.

Talk With Others Who Understand

On myALZteam, the social network for people with Alzheimer’s disease and dementia caregivers, members come together to ask questions, give advice, and share their stories with others who understand life with Alzheimer’s.

Have you tried any new treatments that target tau? What has your experience been like? Post your thoughts in the comments below, or start a conversation on your Activities page.