The Big tau: A new hope for Alzheimer's?

I love coincidences, particularly the ones related to scientific discoveries. In 1975, particle physicists at the Stanford University and University of California in the US published a discovery of a new elementary particle. Twenty years later, the discovery would fetch Martin Perl, the lead physicist, a Nobel Prize in Physics. Following the ancient tradition of naming things using Greek letters, the newly found particle was named "tau"(τ).

In the same year, scientists from the Princeton University in the US published a discovery of a mystery protein in the brain tissue of pigs. Like how bones form the skeleton of the human body, there are protein complexes--microfilaments, microtubules and intermediate filaments--that form the skeleton of our body cells. Microtubules are long tubular structures built from tiny lego-like pieces called tubulins. There are two types of tubulins: alpha and beta. The two combines to form heterodimers. The heterodimers further assemble into microtubules.

When you crush a microtubules into pieces, you find among the pieces individual tubulin dimers, and also, pieces of ring-like structures each consisting 23 tubulin dimers (which can be further broken down to individual dimers). When you try to polymerize the broken pieces, the larger rings easily come together and transform into microtubules. But the individual dimers don't. Some mysterious factor seems to hold the tubulins together and help them to polymerize. Marc Kirschner and colleagues from Princeton discovered that mystery factor to be a protein. Honoring the ancient tradition of naming things using Greek letters, the newly found protein was named "tau"(τ).

In previous studies of in vitro microtubule assembly, it was shown that depolymerized tubules contain two components: the 6S tubulin dimer, and a 36S species which contains about 23 tubulin 6S subunits arranged mainly as double rings. We observed that only the fractions containing 36S rings would repolymerize to form microtubules; the 6S dimer alone would not. ...

We now report that the ability of 36S rings to assemble into microtubules is due to a salt dissociable factor which resides in the 36S species but is absent in the 6S dimer. We have isolated this factor, a protein which is essential for the