Microglia undergoes chemokine receptor, CX3CR1-mediated internalization of extracellular Tau

In Alzheimer’s disease, the microtubule-associated protein, Tau misfolds to form aggregates and filaments in the intra- and extracellular region of neuronal cells. CX3CR1 receptor is involved in monomeric Tau internalization by directly binding to the receptor. In our study, we are interested in understanding the interaction of different pathological structures of Tau with microglial chemokine receptor, CX3CR1 and its role in CX3CR1-mediated Tau internalization by immunofluorescence assay. Co-immunoprecipitation further confirmed the receptor interaction with Tau oligomers and even aggregated filaments. We next determined the role of Tau as a chemoattractant in regulating the migration of microglia by wound healing assay. Further, immunolocalization studies of CX3CR1 with β-arrestin proved the desensitization of CX3CR1 receptor upon Tau binding. Upon ligand interaction, GPCRs undergoes desensitization and encytosed to the cytosol. We have quantified the CX3CR1 internalization by measuring the membrane to cytosol intensity ratio of CX3CR1 receptor upon extracellular Tau exposure. In addition to experimental assays, a comprehensive analysis of the interaction between the CX3CR1 receptor, the Tau protein, and the AZD8797 ligand has been derived from the combined molecular docking, molecular dynamics and free energy calculations using molecular mechanics-generalized Born approach. In particular, two different molecular dynamics simulations were carried out for CX3CR1-Tau protein and AZD8797-bound CX3CR1-Tau protein interaction. The molecular modeling study establishes that AZD8797 binds to CX3CR1 receptor and modulates the Tau interaction with the receptor.