Tau forms protective coat on cytoskeletal filaments
Cytoskeleton is a filamentous network essential for many processes in cells. Among other roles, cytoskeletal filaments serve as tracks for transport of cargoes within cells. This is necessary especially in elongated cells, such as cells of the nervous system and malfunctions in this transport can lead to neurodegeneration.
Tau is an important neuronal factor involved in neurodegenerative diseases, such as the Alzheimers's disease through its self-association into neurofibrillary tangles. International team of scientists from the Institute of Biotechnology, BIOCEV in Prague, Technical University in Dresden and Max Planck Institute of Molecular Cell Biology and Genetics in Dresden present evidence that tau can condense through self-associate onto the surface of cytoskeletal filaments. When in this condensed state, tau forms a layer on the filaments, which selectively regulates the cargo transport on the filament and protects the filaments against degradation mechanisms.
Valerie Siahaan, the first author of the study explains the underlying mechanism: "We found that tau molecules can be bound to the cytoskeletal filaments in two distinct ways, either diffusing along the filament as single independent molecules similar to molecules of water in its liquid state, or bound together into a shell, which coats the filaments, similar as molecules of water when incorporated in its solid state - ice. This "ice crust" on the filaments protects the filament and selectively allows only those molecules to pass, that have a special ability and can so to say walk on ice."
The paper shows that tau self-association is not only related to pathological states and neurodegeneration, but might be physiological molecular process for tau to perform its roles in cells.
Original paper: Siahaan, V., Krattenmacher, J., Hyman, A. A., Diez, S., Hernández-Vega, A., Lansky, Z., & Braun, M. (2019). Kinetically distinct phases of tau on microtubules regulate kinesin motors and severing enzymes. Nature Cell Biology, 1–11. http://doi.org/10.1038/s41556-019-0374-6