Professor Donna Wilcock describes neurofibrillary tangles, which form inside the neuron in Alzheimer's disease and are composed of tau proteins.
Neurofibrillary tangles – I’m going to say 'tangles' to make this simpler. Now we’re talking about intracellular proteins. So neurofibrillary tangles form inside the neuron and these are composed of abnormally processed tau. Tau is associated with the microtubules, which, if you think about the neuron, you have the cell body and then you have the axon, which can run for many, many centimeters (meters in some cases) and along the axon you have train tracks called microtubules that are involved in transport of something from the cell body to the synapse. Tau is thought to be involved in the movement of proteins, anything really, from the cell body to the axon. Tau in Alzheimer’s disease gets what we call hyper-phosphorylated, which means that you add phosphate groups to the protein. When you do this in an abnormal fashion, the tau moves away from the microtubule and will aggregate. So, it’s the same as the amyloid beta, which is you will get multiple tau proteins coming together and clumping up, but this time they clump up inside the cell. When they clump up inside the cell, we believe that this causes the neuron to become stressed and eventually die.