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What Are Amyloid Plaques?

Amyloid plaques refer to protein deposits that appear in the brains of Alzheimer's disease patients. Alzheimer's is a type of incurable dementia that typically affects adults over 65 years of age. Scientists have not determined the exact role amyloid plaques play in the disease, but they likely contribute to neuronal death and brain atrophy.

  1. History

    • German scientist and doctor, Alois Alzheimer, first recognized amyloid plaques in an elderly patient whose case study and autopsy results he presented in 1906. Better microscopes and techniques for staining brain tissue helped Dr. Alzheimer distinguish the sticky proteins, now called amyloid plaques, in the neurons of his patient's brain.

    Basics

    • Amyloid plaques are composed mostly of fragments of beta-amyloid peptide, an insoluble protein. The plaques also contain other proteins and remnants of other cellular material. Amyloid plaques develop in the spaces between neurons, or the brain's nerve cells, starting with the neurons that control memory. The accumulation of plaques between neurons makes it more difficult for neurons to communicate with each other, which eventually leads to neuronal death.

    Symptom or Cause?

    • Scientists once believed amyloid plaques cause Alzheimer's disease. However, some research suggests that amyloid plaques are merely a symptom of Alzheimer's, not the underlying cause. Research investigating the development of amyloid plaques has found that certain enzymes affect amyloid precursor protein, the protein that sometimes develops into amyloid plaques, in different ways. Some enzymes create beta-amyloid peptide, the protein that makes up amyloid plaques, while others do not. Further research into these enzymes may reveal more information about how Alzheimer's develops.

    Relationship to Tangles

    • Amyloid plaques aren't the only substances clogging up the spaces between neurons. Neurofibrillary tangles, which refer to clumps of a protein called tau, also develop in the brains of Alzheimer's patients. Like amyloid plaques, neurofibrillary tangles inhibit communication among neurons and contribute to neuronal death.

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