Tau proteins are members of the microtubule associated proteins (MAPs), and are predominantly expressed in neurons and enriched in the axonal compartment. These proteins are involved in many diseases therefore termed tauopathies . In the disease, tau is present in a hyperphosphorylated state that forms aggregates in the somato-dentritic compartment. In order to analyse the distribution of normal and tau proteins present in tauopathies in living cells, a pulse-escape fluorescence photoactivation approach was developed. A wild type wt , a R406W mutant mut , a hyperphosphorylation model PHP (pseudohyperphosphorylated), and a smaller fragment delta tau protein, and a control PA-GFPx3 were fused to the photoactivatable GFP protein. These proteins were expressed in differentiated PC12 cells and mice primary cortical cultures, and analysed in photoactivation experiments. The data showed that the wt protein was less mobile, both at the shaft or the tip of cell processes, than the delta or control proteins (higher immobile fraction, IF ). This could be attributed to the microtubule binding domain present only in the wt. Treatment of cells with drugs to disrupt microtubules, or detach tau from the filaments confirmed this interpretation. The mut mobility was comparable to that seen for the wt, suggesting that the interaction with microtubules was unaffected by the mutation. The PHP showed a lower IF compared to the wt, in agreement with a lower binding to microtubules. Furthermore, this behaviour could be reproduced by increasing the level of phosphorylation of the wt by drug treatment. A flux analysis was performed to determine the fraction of protein moving towards the distal or proximal portion of the process. Only delta and wt detached from the microtubules showed an increased flux towards the tip.The results suggest that the plasma membrane interaction is involved in the flux of wt tau proteins towards the distal portion.
| Identifer | oai:union.ndltd.org:uni-osnabrueck.de/oai:repositorium.ub.uni-osnabrueck.de:urn:nbn:de:gbv:700-2007122812 |
| Date | 27 December 2007 |
| Creators | Weissmann, Carina |
| Contributors | Prof Dr. R. Brandt, Prof. Dr. A. Paululat |
| Source Sets | Universität Osnabrück |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/zip, application/pdf |
| Rights | http://rightsstatements.org/vocab/InC/1.0/ |
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