In-Cell NMR Study of Tau and MARK2 Phosphorylated Tau

• Published in: International journal of molecular sciences 2018-12, Vol.20 (1), p.90
• Main Authors: Zhang, Shengnan, Wang, Chuchu, Lu, Jinxia, Ma, Xiaojuan, Liu, Zhenying, Li, Dan, Liu, Zhijun, Liu, Cong
• Format: Article
• Language: English
• Subjects: Actins - chemistry; Alzheimer Disease - metabolism; Alzheimer Disease - pathology; Aqueous solutions; Atomic structure; Binding; Biological activity; Biomolecules; Disease; Dynamic structural analysis; Electroporation; Escherichia coli; Glycerol; HEK293 Cells; Humans; in-cell NMR; Intracellular; Kinases; Mammalian cells; Mammals; MARK2 phosphorylation; Microtubules - chemistry; Nuclear Magnetic Resonance, Biomolecular; Phosphorylation; Physiology; Post-translation; Protein-Serine-Threonine Kinases - metabolism; Protein-serine/threonine kinase; Proteins; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Residues; Spectrum analysis; Structure-function relationships; Studies; Tau; Tau protein; tau Proteins - chemistry; tau Proteins - genetics; tau Proteins - metabolism
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms20010090

The intrinsically disordered protein, Tau, is abundant in neurons and contributes to the regulation of the microtubule (MT) and actin network, while its intracellular abnormal aggregation is closely associated with Alzheimer's disease. Here, using in-cell Nuclear Magnetic Resonance (NMR) spectroscopy, we investigated the conformations of two different isoforms of Tau, Tau40 and k19, in mammalian cells. Combined with immunofluorescence imaging and western blot analyses, we found that the isotope-enriched Tau, which was delivered into the cultured mammalian cells by electroporation, is partially colocalized with MT and actin filaments (F-actin). We acquired the NMR spectrum of Tau in human embryonic kidney 293 (HEK-293T) cells, and compared it with the NMR spectra of Tau added with MT, F-actin, and a variety of crowding agents, respectively. We found that the NMR spectrum of Tau in complex with MT best recapitulates the in-cell NMR spectrum of Tau, suggesting that Tau predominantly binds to MT at its MT-binding repeats in HEK-293T cells. Moreover, we found that disease-associated phosphorylation of Tau was immediately eliminated once phosphorylated Tau was delivered into HEK-293T cells, implying a potential cellular protection mechanism under stressful conditions. Collectively, the results of our study reveal that Tau utilizes its MT-binding repeats to bind MT in mammalian cells and highlight the potential of using in-cell NMR to study protein structures at the residue level in mammalian cells.