@article {47164, title = {Baicalein suppresses repeat tau fibrillization by sequestering oligomers}, journal = {Archives of Biochemistry and Biophysics}, volume = {675}, year = {2019}, month = {OCT}, pages = {108119}, type = {Article}, abstract = {

Alzheimer{\textquoteright}s disease (AD) is a neurodegenerative disorder caused by protein misfolding, aggregation and accumulation in the brain. A large number of molecules are being screened against these pathogenic proteins but the focus for therapeutics is shifting towards the natural compounds as aggregation inhibitors, mainly due to their minimum adverse effects. Baicalein is a natural compound belonging to the class of flavonoids isolated from the Chinese herb Scutellaria baicalensis. Here we applied fluorescence, absorbance, microscopy, MALDI-TOF spectrophotometry and other biochemical techniques to investigate the interaction between Tau and Baicalein in vitro. We found the aggregation inhibitory properties of Baicalein for the repeat Tau. Overall, the potential of Baicalein in dissolving the preformed Tau oligomers as well as mature fibrils can be of utmost importance in therapeutics for Alzheimer{\textquoteright}s disease.

}, keywords = {Alzheimer disease, Baicalein, Microtubule assembly, Paired helical filaments, Protein aggregation, tau protein}, issn = {0003-9861}, doi = {10.1016/j.abb.2019.108119}, author = {Sonawane, Shweta Kishor and Balmik, Abhishek Ankur and Boral, Debjyoti and Ramasamy, Sureshkumar and Chinnathambi, Subashchandrabose} } @article {46842, title = {Effect of melatonin on tau aggregation and tau-mediated cell surface morphology}, journal = {International Journal of Biological Macromolecules}, volume = {152}, year = {2020}, month = {JUN }, pages = {30-39}, type = {Article}, abstract = {

Aggregation of Microtubule-associated protein Tau and its deposition in the form of neurofibrillary tangles (NFTs) is one of the pathological hallmarks of Alzheimer{\textquoteright}s disease (AD). Tau aggregation inhibition has been targeted in various studies including natural compounds and synthetic small molecules. Here, we have studied neurohormone- Melatonin against in vitro Tau aggregation and observed its effect on membrane topology, tubulin network and Tau phosphorylation in Neuro2A and N9 cell lines. The aggregation and conformation of Tau was determined by ThT fluorescence and CD spectroscopy respectively. The morphology of Tau aggregates in presence and absence of Melatonin was studied by transmission electron microscopy. Melatonin was found to reduce the formation of higher order oligomeric structures without affecting the overall aggregation kinetics of Tau. Melatonin also modulates and helps to maintain membrane morphology, independent on tubulin network as evidenced by FE-SEM and immunofluorescence analysis. Overall, Melatonin administration shows mild anti-aggregation and cytoprotective effects. (C) 2020 Elsevier B.V. All rights reserved.

}, keywords = {Alzheimer{\textquoteright}s disease, Cell surface morphology, melatonin, Paired helical filaments, tau protein, Tauopathies}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2020.01.296}, author = {Das, Rashmi and Balmik, Abhishek Ankur and Chinnathambi, Subashchandrabose} } @article {46945, title = {Melatonin interacts with repeat domain of Tau to mediate disaggregation of paired helical filaments}, journal = {Biochimica Et Biophysica Acta-General Subjects}, volume = {1864}, year = {2020}, month = {MAR}, pages = {129467}, type = {Article}, abstract = {

Tau is the major neuronal protein involved in the stabilization of microtubule assembly. In Alzheimer{\textquoteright}s disease, Tau self-assembles to form intracellular protein aggregates which are toxic to cells. Various methods have been tried and tested to restrain the aggregation of Tau. Most of the agents tested for this purpose have limitations in their effectiveness and availability to neuronal cells. We have tested melatonin, a neurohormone secreted by pineal gland and a well-known anti-oxidant, for its ability to interact with the repeat domain of Tau using ITC and NMR. In aggregation inhibition and disaggregation studies of repeat Tau, melatonin was found to modulate the aggregation propensity of repeat Tau at a concentration of 5000 mu M and was more effective in dissolving preformed aggregates rather than acting as an aggregation inhibitor. However, there were no major conformational changes in Tau in presence of melatonin as observed by CD spectroscopy. On the basis of our findings, we are proposing a mechanism by which melatonin can interact with the repeat domain of Tau and exhibit its disaggregation effect.

}, keywords = {Alzheimer{\textquoteright}s disease, Disaggregation, melatonin, Paired helical filaments, tau protein, Tauopathies}, issn = {0304-4165}, doi = {10.1016/j.bbagen.2019.129467}, author = {Balmik, Abhishek Ankur and Das, Rashmi and Dangi, Abha and Gorantla, Nalini Vijay and Marelli, Udaya Kiran and Chinnathambi, Subashchandrabose} } @article {46609, title = {Role of cysteines in accelerating Tau filament formation}, journal = {Journal of Biomolecular Structure \& Dynamics}, volume = {40}, year = {2022}, month = {JUN}, pages = {4366-4375}, type = {Article}, abstract = {

Alzheimer{\textquoteright}s disease is majorly associated with intracellular accumulation of Tau into paired helical filaments and tangles. The self-aggregated dimeric and oligomeric species of Tau formed are more toxic to neuronal cells and acts as seeds for filament formation. The two cysteine residues and the two hexapeptide regions of full-length Tau play a key role in initialization and filament formation during Tau aggregation. The role of cysteine residues in Tau aggregation has been studied by in-vitro aggregation assay that was measured by Thioflavin S fluorescence to observe the kinetics of aggregation. In this study, we have performed in-vitro aggregation assay with recombinant full-length Tau and the cysteine mutants to understand the mechanism of cysteine independent Tau aggregation. Here, we report that cysteine mutant full-length Tau can aggregate to form filaments under in-vitro conditions. To visualize the polymorphisms of Tau and cysteine mutants under different aggregation conditions anionic cofactor, heparin was employed. Wild-type Tau showed rapid aggregation to form oligomers and filaments. On the other hand, the cysteine mutant delayed the initial Tau aggregation. This indicates the importance of cysteine residues in accelerating initial Tau nucleation for its aggregation. The filament morphology of wild-type and cysteine mutant Tau has been characterized using transmission electron microscopy and high-resolution transmission electron microscopy. Communicated by Ramaswamy H. Sarma

}, keywords = {Heparin-induced aggregation, Paired helical filaments, Tau Aggregation, Tau Oligomers, tau protein}, issn = {0739-1102}, doi = {10.1080/07391102.2020.1856720}, author = {Chidambaram, Hariharakrishnan and Chinnathambi, Subashchandrabose} }