Journal Article

Phosphorylation of tau at Y18, but not tau-fyn binding, is required for tau to modulate NMDA receptor-dependent excitotoxicity in primary neuronal culture

Miyamoto, Takashi, Thomas, Reuben, Stein, Liana, Mucke, Lennart, Taneja, Praveen, Djukic, Biljana, Vossel, Keith, Knox, Joseph

2017

Overview

Background Hyperexcitability of neuronal networks can lead to excessive release of the excitatory neurotransmitter glutamate, which in turn can cause neuronal damage by overactivating NMDA-type glutamate receptors and related signaling pathways. This process (excitotoxicity) has been implicated in the pathogenesis of many neurological conditions, ranging from childhood epilepsies to stroke and neurodegenerative disorders such as Alzheimer’s disease (AD). Reducing neuronal levels of the microtubule-associated protein tau counteracts network hyperexcitability of diverse causes, but whether this strategy can also diminish downstream excitotoxicity is less clear. Methods We established a cell-based assay to quantify excitotoxicity in primary cultures of mouse hippocampal neurons and investigated the role of tau in exicitotoxicity by modulating neuronal tau expression through genetic ablation or transduction with lentiviral vectors expressing anti-tau shRNA or constructs encoding wildtype versus mutant mouse tau. Results We demonstrate that shRNA-mediated knockdown of tau reduces glutamate-induced, NMDA receptor-dependent Ca 2+ influx and neurotoxicity in neurons from wildtype mice. Conversely, expression of wildtype mouse tau enhances Ca 2+ influx and excitotoxicity in tau-deficient ( Mapt −/− ) neurons. Reconstituting tau expression in Mapt −/− neurons with mutant forms of tau reveals that the tau-related enhancement of Ca 2+ influx and excitotoxicity depend on the phosphorylation of tau at tyrosine 18 (pY18), which is mediated by the tyrosine kinase Fyn. These effects are most evident at pathologically elevated concentrations of glutamate, do not involve GluN2B–containing NMDA receptors, and do not require binding of Fyn to tau’s major interacting PxxP motif or of tau to microtubules. Conclusions Although tau has been implicated in diverse neurological diseases, its most pathogenic forms remain to be defined. Our study suggests that reducing the formation or level of pY18-tau can counteract excitotoxicity by diminishing NMDA receptor-dependent Ca 2+ influx.

• Publisher: BioMed Central,Springer Nature B.V,BMC
• Subject: Alzheimer's disease / Animals / Biomedical and Life Sciences / Biomedicine / Calcium / Calcium influx / Cell culture / Cells, Cultured / Children / Competition / Disease / Excitatory Amino Acid Agents - pharmacology / Excitotoxicity / Expression vectors / Fyn / Fyn protein / Gene expression / Glutamic acid receptors (ionotropic) / Hippocampus / Hippocampus - drug effects / Hippocampus - metabolism / Kinases / Mice / Mice, Inbred C57BL / Mice, Knockout / Microtubule-associated proteins / Molecular Medicine / N-Methyl-D-aspartic acid receptors / Neural networks / Neurodegeneration / Neurodegenerative diseases / Neurological diseases / Neurology / Neurons / Neurons - drug effects / Neurons - metabolism / Neurosciences / Neurotoxicity / NMDARs / Phosphorylation / Protein-tyrosine kinase / Proteins / Proto-Oncogene Proteins c-fyn - metabolism / Receptors, N-Methyl-D-Aspartate - drug effects / Receptors, N-Methyl-D-Aspartate - metabolism / Research Article / Rodents / Signal transduction / Stroke / Tau / Tau protein / tau Proteins - metabolism / Transgenic animals