Tau proteins are microtubule-associated proteins found in neurons in the brain. They were discovered in 1975 in Marc Kirschner's laboratory at Princeton University //www.pnas.org/cgi/content/abstract/72/5/1858 Weingarten et al., 1975.

Tau proteins interact with tubulin to stabilize microtubules and promote tubulin assembly into microtubules. Tau has two ways of controlling microtubule stability: isoforms and phosphorylation.

Six tau isoforms exist, and they are distinguished by their number of binding domains. Three isoforms have three binding domains and the other three have four binding domains. The binding domains are located in the carboxy-terminus of the protein and are positively-charged (allowing it to bind to the negatively-charged microtubule). The isoforms with four binding domains are better at stabilizing microtubules than those with three binding domains. The isoforms are a result of alternative splicing in exons 2,3, and 10 of the tau gene.

Phosphorylation of tau is regulated by a host of kinases. For example, PKN, a serine/threonine kinase. When PKN is activated, it phosphorylates tau, resulting in disruption of microtubule organization //www.jbc.org/cgi/content/full/276/13/10025 Taniguchi et al., 2001.

Hyperphosphorylation of the tau protein, however, results in the self-assembly of tangles of paired helical filaments and straight filaments, which are involved in the pathogenesis of Alzheimer's disease and other tauopathies //www.pnas.org/cgi/content/full/98/12/6923 Alonso et al., 2001.

References

Alonso, A. del C., Zaidi, T., Novak, M., Grundke-Iqbal, I., Iqbal, K. (2001) Hyperphosphorylation induces self-assembly of tau into tangles of paired helical filaments/straight filaments. PNAS. (98) 6923-8. http://www.pnas.org/cgi/content/full/98/12/6923

Delacourte, A. (2005) Tauopathies: recent insights into old diseases. Folia Neuropathol (43) 244-257. http://www.new.termedia.pl/magazine.php?magazine_id=20&article_id=5368&magazine_subpage=FULL_TEXT

Hirokawa, N., Shiomura, Y., Okabe, S. (1988) Tau proteins: the molecular structure and mode of binding on microtubules. J Cell Biol. (107) 1449-59. http://www.jcb.org/cgi/reprint/107/4/1449

Taniguchi, T., Kawamata, T., Mukai, H., Hasegawa, H., Isagawa, T., Yasuda, M., Hashimoto, T., Terashima, A., Nakai, M., Mori, H., Ono, Y., Tanaka, C. (2001) Phosphorylation of tau is regulated by PKN. J Biol Chem. (276) 10025-31. http://www.jbc.org/cgi/content/full/276/13/10025

Weingarten, MD., Lockwood, AH., Hwo, SY., Kirschner, MW. (1975) A protein factor essential for microtubule assembly. PNAS. (72) 1858-1862. http://www.pnas.org/cgi/content/abstract/72/5/1858

Proteins