Dangerous mistaken identity

(Press-News.org) This news release is available in German.

Proteins like the so-called heat shock protein Hsp90 play an important role in almost all processes within human cells. They help other proteins fold into their three-dimensional structure or return damaged proteins back into their proper shape.

Recently, there has been increasing evidence indicating that the heat shock protein HSP90 may also be involved in the folding processes of the tau protein. Deposits of tau proteins in brain cells are typical for Alzheimer's disease and are held responsible for decaying nerve cells.

However, while dissolved tau proteins look more like long, stretched chains, HSP90 binds predominantly proteins that have already been prefolded. This contradiction has now been resolved by an international team headed by Dr. Tobias Madl, leader of the BioSysNet Working Group and TUM Junior Fellow at the Technische Universität München and leader of the Emmy-Noether Group Structural Biology of Signal Transduction at the Institute of Structural Biology at the Helmholz Zentrum München, as well as Prof. Stefan Rüdiger from the Dutch University of Utrecht.

Detective work

Using a combination of very different techniques like magnetic resonance spectroscopy, small-angle X-ray scattering and computer modeling, they successfully determined structure and dynamics of the interactions between the two biomolecules: For Hsp90 the tau protein looks like a prefolded larger protein. Furthermore they were able to deduce how Hsp90 influences the aggregation of tau proteins with one another.

"Deposits of tau proteins can cause Alzheimer's disease. We have discovered the protein regions in which the proteins interact. This is a novel and important starting point for influencing structural formation and for developing future therapies for Alzheimer's disease," says Madl.

In addition to Alzheimer's disease, further neuro-degenerative diseases are caused by protein aggregation. Chaperones also play a role in the development of cancer and cystic fibrosis. These scientific insights thus provide an important basis for better understanding the disease mechanisms.

INFORMATION: The research was funded by the European Community, the German Research Foundation (DFG), the Dutch Organization for Scientific Research (NWO), the Austrian Academy of Sciences, the Portugese Fundação para a Ciência e a Tecnologia and the National Institutes of Health (USA), as well as the Bavarian Ministry of Science and Research. The small-angle X-ray scattering (SAXS) experiments were conducted in the outstation of the EMBL at DESY in Hamburg. The computer modeling was done at the Leibniz Supercomputing Center of the Bavarian Academy of Sciences.

Publication:

Karagoz, G. E. et al., Hsp90-Tau Complex Reveals Molecular Basis for Specificity in Chaperone Action. Cell, 156, (5), 963-974 Doi: 10.1016/j.cell.2014.01.037