Microtubules are analogous to a rail network along which other particles are transported from one location to another inside cells. In the case of nerve cells, long projections called axons can be from a fraction of a centimetre in length to more than one metre long and it is the microtubules that play an essential role in delivering material along these projections, a function that if it fails results in the affected nerve cells dying. In AD, the tau that is assembled into the PHF has an excessive amount of phosphate attached to it and is said to be hyperphosphorylated. Nerve cells in AD brain that contain many PHF have lost their complement of microtubules and it appears that the PHF have clogged-up the inside of the affected nerve cells. Since experiments have shown this hyperphosphorylated tau is unable to bind to and stabilise microtubules in an assembled state, then this may be why the microtubules disappear at the same time as the hyperphosphorylated tau aggregates into PHF, both events contributing to the death of the nerve cells.
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6/6/2012 2:43:17 PM - 220.127.116.11