How do amyloid beta and tau proteins affect nerve cells in Alzheimer disease?

In Alzheimer disease, amyloid beta and tau proteins contribute to brain pathology through the formation of distinct structures that interfere with normal cellular function.1

Amyloid Beta and Neuritic Plaques

Amyloid beta is a sticky protein derived from the amyloid precursor protein. In patients with Alzheimer disease, this protein clumps together to form neuritic plaques—also known as senile or amyloid plaques—which consist of deteriorating neuronal material surrounding these deposits. These plaques are thought to destroy healthy brain tissue and disrupt normal cellular processes. Some research suggests that plaque formation may be an abnormal or excessive response to brain infection.12

Tau and Neurofibrillary Tangles

Tau is a protein that normally occurs within neurons. In Alzheimer disease, tau molecules are incorrectly processed and clump together into twisted fibers known as neurofibrillary tangles. These tangles accumulate within the cytoplasm of nerve cells, particularly in the cerebral cortex and hippocampus, and are considered a hallmark of the disease's progression.13

While both plaques and tangles are associated with the disease, it remains unclear whether they are the primary cause or a consequence of the underlying pathology.1