@article {47124, title = {Alpha-Linolenic acid modulates phagocytosis and endosomal pathways of extracellular Tau in microglia}, journal = {Cell Adhesion \& Migration}, volume = {15}, year = {2021}, month = {JAN }, pages = {84-100}, type = {Article}, abstract = {

Microglia, the resident immune cells, were found to be activated to inflammatory phenotype in Alzheimer{\textquoteright}s disease (AD). The extracellular burden of amyloid-beta plaques and Tau seed fabricate the activation of microglia. The seeding effect of extracellular Tau species is an emerging aspect to study about Tauopathies in AD. Tau seeds enhance the propagation of disease along with its contribution to microglia-mediated inflammation. The excessive neuroinflammation cumulatively hampers phagocytic function of microglia reducing the clearance of extracellular protein aggregates. Omega-3 fatty acids, especially docosahexaenoic acid and eicosapentaenoic acid, are recognized to induce anti-inflammatory phenotype of microglia. In addition to increased cytokine production, omega-3 fatty acids enhance phagocytic receptors expression in microglia. In this study, we have observed the phagocytosis of extracellular Tau in the presence of alpha-linolenic acid (ALA). The increased phagocytosis of extracellular Tau monomer and aggregates have been observed upon ALA exposure to microglia cells. After internalization, the degradation status of Tau has been studied with early and late endosomal markers Rab5 and Rab7. Further, the lysosome-mediated degradation of internalized Tau was studied with LAMP-2A, a lysosome marker. The enhanced migratory ability in the presence of ALA could be beneficial for microglia to access the target and clear it. The increased migration of microglia was found to induce the microtubule-organizing center repolarization. The data indicate that the dietary fatty acids ALA could significantly enhance phagocytosis and intracellular degradation of internalized Tau. Our results suggest that microglia could be influenced to reduce extracellular Tau seed with dietary fatty acids.

}, keywords = {alpha-linolenic acid, endosomal markers, Fatty acids, MTOC repolarization, Phagocytosis, Tauopathy}, issn = {1933-6918}, doi = {10.1080/19336918.2021.1898727}, author = {Desale, Smita Eknath and Chinnathambi, Subashchandrabose} } @article {47056, title = {Phosphoinositides signaling modulates microglial actin remodeling and phagocytosis in Alzheimer{\textquoteright}s disease}, journal = {Cell Communication and Signaling}, volume = {19}, year = {2021}, month = {FEB}, pages = {28}, type = {Review}, abstract = {

Alzheimer{\textquoteright}s disease is one of the neurodegenerative diseases, characterized by the accumulation of abnormal protein deposits, which disrupts signal transduction in neurons and other glia cells. The pathological protein in neurodegenerative diseases, Tau and amyloid-P contribute to the disrupted microglial signaling pathways, actin cytoskeleton, and cellular receptor expression. The important secondary messenger lipids i.e., phosphatidylinositols are largely affected by protein deposits of amyloid-beta in Alzheimer{\textquoteright}s disease. Phosphatidylinositols are the product of different phosphatidylinositol kinases and the state of phosphorylation at D3, D4, and D5 positions of inositol ring. Phosphatidylinositol 3,4,5-triphosphate (PI 3, 4, 5-P3) involves in phagocytic cup formation, cell polarization, whereas Phosphatidylinositol 4,5-bisphosphate (PI 4, 5-P2)-mediates the process of phagosomes formation and further its fusion with early endosome.. The necessary activation of actin-binding proteins such as Rac, WAVE complex, and ARP2/3 complex for the actin polymerization in the process of phagocytosis, migration is regulated and maintained by PI 3, 4, 5-P3 and PI 4, 5-P2. The ratio and types of fatty acid intake can influence the intracellular secondary lipid messengers along with the cellular content of phaphatidylcholine and phosphatidylethanolamine. The Amyloid-beta deposits and extracellular Tau seeds disrupt phosphatidylinositides level and actin cytoskeletal network that hamper microglial-signaling pathways in AD. We hypothesize that being a lipid species intracellular levels of phosphatidylinositol would be regulated by dietary fatty acids. Further we are interested to understand phosphoinositide-based signaling cascades in phagocytosis and actin remodeling.

}, keywords = {actin remodeling, Alzheimer{\textquoteright}s disease, Dietary fatty acids, Phagocytosis, Phosphoinositides, PI3K signaling}, doi = {10.1186/s12964-021-00715-0}, author = {Desale, Smita Eknath and Chinnathambi, Subashchandrabose} } @article {47803, title = {G-protein coupled purinergic P2Y12 receptor interacts and internalizes TauRD-mediated by membrane-associated actin cytoskeleton remodeling in microglia}, journal = {European Journal of Cell Biology}, volume = {101}, year = {2022}, month = {APR}, pages = {151201}, type = {Article}, abstract = {In Alzheimer{\textquoteright}s disease, the microtubule-associated protein, Tau misfolds to form aggregates and filaments in the intra- and extracellular region of neuronal cells. Microglial cells are the resident brain macrophage cells involved in constant surveillance and activated by the extracellular deposits. Purinergic receptors are involved in the chemotactic migration of microglial cells towards the site of inflammation. From our recent study, we have observed that the microglial P2Y12 receptor is involved in phagocytosis of full-length Tau species such as monomers, oligomers and aggregates by actin-driven chemotaxis. This study shows the interaction of repeat-domain of Tau (TauRD) with the microglial P2Y12 receptor and the corresponding residues for interaction have been analysed by various in-silico approaches. In the cellular studies, TauRD was found to interact with microglial P2Y12R and induces its cellular expression confirmed by co-immunoprecipitation and western blot analysis. Furthermore, the P2Y12R-mediated TauRD internalization has demonstrated activation of microglia with an increase in the Iba1 level, and TauRD becomes accumulated at the peri-nuclear region for the degradation. Similarly, immunofluorescence microscopic studies emphasized that TauRD is phagocytosed by microglial P2Y12R via the membrane-associated actin remodeling as filopodia extension. Upon internalization, we have demonstrated the P2Y12R signaling-mediated degradation of accumulated TauRD by lysosomal pathway. Altogether, microglial P2Y12R interacts with TauRD and mediates directed migration and activation for its internalization and degradation.}, keywords = {Alzheimer{\textquoteright}s disease, Internalization, microglia, P2Y12R, Phagocytosis, Tau}, issn = {0171-9335}, doi = {https://doi.org/10.1016/j.ejcb.2022.151201}, url = {https://www.sciencedirect.com/science/article/pii/S0171933522000048}, author = {Chidambaram, Hariharakrishnan and Das, Rashmi and Chinnathambi, Subashchandrabose} } @article {48361, title = {G-protein coupled purinergic P2Y12 receptor interacts and internalizes Tau(RD)-mediated by membrane-associated actin cytoskeleton remodeling in microglia}, journal = {European Journal of Cell Biology}, volume = {101}, year = {2022}, month = {APR}, pages = {151201}, type = {Article}, abstract = {

In Alzheimer{\textquoteright}s disease, the microtubule-associated protein, Tau misfolds to form aggregates and filaments in the intra- and extracellular region of neuronal cells. Microglial cells are the resident brain macrophage cells involved in constant surveillance and activated by the extracellular deposits. Purinergic receptors are involved in the chemotactic migration of microglial cells towards the site of inflammation. From our recent study, we have observed that the microglial P2Y12 receptor is involved in phagocytosis of full-length Tau species such as monomers, oligomers and aggregates by actin-driven chemotaxis. This study shows the interaction of repeat-domain of Tau (Tau(RD)) with the microglial P2Y12 receptor and the corresponding residues for interaction have been analysed by various in-silico approaches. In the cellular studies, Tau(RD) was found to interact with microglial P2Y12R and induces its cellular expression confirmed by co-immunoprecipitation and western blot analysis. Furthermore, the P2Y12R-mediated Tau(RD) internalization has demonstrated activation of microglia with an increase in the Iba1 level, and Tau(RD) becomes accumulated at the peri-nuclear region for the degradation. Similarly, immunofluorescence microscopic studies emphasized that Tau(RD) is phagocytosed by microglial P2Y12R via the membrane-associated actin remodeling as filopodia extension. Upon internalization, we have demonstrated the P2Y12R signaling-mediated degradation of accumulated Tau(RD) by lysosomal pathway. Altogether, microglial P2Y12R interacts with Tau(RD) and mediates directed migration and activation for its internalization and degradation.

}, keywords = {Alzheimer{\textquoteright}s disease, Internalization, microglia, P2Y12R, Phagocytosis, Tau(RD)}, issn = {0171-9335}, doi = {10.1016/j.ejcb.2022.151201}, author = {Chidambaram, Hariharakrishnan and Das, Rashmi and Chinnathambi, Subashchandrabose} }