Chapter 21 : Tau Proteins

On this journey that I have been on I have kept coming across Tau proteins.  I have no alternative. I have to tell people a small part of what I have learnt about Tau proteins.

How many Tau proteins do you have? What are they? Tau is used to describe a group of proteins that exist in the cerebra-spinal fluid that primarily stabilize microtubules.  They are present in the liquid (the CSF) containing the nerves. They are not present in other fluids such as blood. When they are defective and don’t work properly it is commonly a sign that the person has Alzheimer’s Disease (AD) or Parkinson’s Disease.

One of the main functions of TAU proteins is to modulate the stability of axonal microtubules. In a healthy CNS the transport system is arranged in parallel rows. Food and waste travel along these rows or tracks. Tau proteins bind to microtubules to help keep the tracks straight.  Excessive or abnormal phosphorylation of tau results in the transformation of normal adult tau into PHF-tau (paired helical filament-Tau) and NFTs (neurofibrillary tangles) which don’t work as well. Phosphorylation of tau proteins means your brain doesn’t work as well. What causes phosphorylation of tau proteins? Kinases play a role. What are kinases and do you control them? That is a big question which I will look into.

Traumatic Brain Injury

High levels of tau in the CNS leads to poor recovery after head injury.  And head injury leads to high levels of tau in the CSF. Or head injuries can lead to a poor recovery from head injury. Repetitive mild trauma such as in boxing can lead to NFTs which can slow recovery from brain trauma.

When is a test for Tau proteins taken?

One time is Alzheimer Disease.  It is a supplemental test used to aid in diagnose. Typically done after a series of other tests where the practitioner first tests the function of the brain. In a symptomatic person a low Aβ 42 level along with a high tau level reflects an increased likelihood of AD. It may also indicate a rapid progression of the disease.

In Alzheimer’s disease (AD), total CSF beta amyloid (Aβ) is not significantly different from controls but Aβ42 is decreased probably because it is deposited in plaques and is not available in a diffusible form. Total-tau (t-tau) and phosphorylated tau (p-tau) are both increased in AD due to neural death and the release of tau into the extracellular space.

Another time a tau test is done is when trauma results in excess fluid in the ear or nose and it is not known where the fluid comes from.  A physical injury to the head will cause membranes covering the brain to break and CSF to leak out. A test to determine if the fluid is CSF is needed.  Time for a Tau test.