Analysis of Tau LLPS in Neurodegenerative Diseases

Tau is a microtubule-associated neuronal intrinsically disordered protein (IDP) involved in microtubule stabilization and regulates axon growth and transport in neurons. Studies have shown that purified tau can undergo liquid-liquid phase separation (LLPS) in vitro to form biomolecular condensates. However, the liquid-to-solid transition that leads to abnormal tau aggregation plays a crucial role in the pathogenesis of neurodegenerative diseases (collectively known as Tau diseases). These disorders include Alzheimer's disease (AD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), gammophile granulomatosis, piker's disease (PiD), some forms of frontotemporal dementia (FTD), and chronic traumatic encephalopathy (CTE). One of the key histopathological features of all these diseases is the accumulation of insoluble cytoplasmic tau in the brain.

Fig. 1. Phase transitions of tau in physiology and disease. (Rai SK, et al., 2021)

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Similar to many other native nonstructural proteins, tau undergoes LLPS in cells as well as in test tubes. Tau can aggregate into different inclusions such as neurogenic fibrillary tangles (NFT), neurofibrillary filaments (NT), picosomes, and other forms of deposits that are hallmarks of many neurodegenerative diseases. These neurodegenerative diseases can be avoided by preventing the accumulation of tua.

Here, CD BioSciences offers specialized services to analyze LLPS in neurodegenerative diseases in vitro and in vivo. Our technical team can capture the current state of the science and comprehensively analyze the interesting molecular mechanisms of tau phase separation. Our lab provides a blend of existing and emerging biophysical tools to achieve unique spatio-temporal resolution data over a wide range of lengths and time scales.

The following quantitative biophysical measurements of tau LLPS are offered by our services:

• Prediction of tau phase-separated sequences. We offer a range of bioinformatics tools to predict the inherent disorder and phase separation propensity of tau.
• Analysis of tau thermal response phase behavior.
• Analysis of the conformational dynamics of tau in condensates. We provide fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy, fluorescence anisotropy measurements, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopy techniques to enable analysis of tau conformational and dynamic properties over a wide range of time scales from picoseconds to seconds.

In addition, we develop modulation strategies for tau-focused intracellular LLPS, including:

• Modulation of tau phase separation by RNA, heparin and ligands (molecular crowding agents, metal ions and salts).
• Modulation of tau phase separation by protein interactions.
• Modulation of tau phase behavior by changing protein structure. We can analyze multiple PTMs of tau, including phosphorylation, acetylation, glycosylation, glycosylation and ubiquitination.

Furthermore, we systematically integrate these regulatory approaches with proteomic, transcriptomic, imaging, genetic, and epidemiological data to explore the pathogenesis of abnormal phase changes in tau and to develop potential therapeutic targets to prevent and treat these neurodegenerative diseases.

CD BioSciences aims to analyze the regulation of tau LLPS to develop potential therapeutic approaches for neurodegenerative diseases. If you are interested in our services, please feel free to contact us.