Opposing regulation of tau protein levels by ionotropic and metabotropic glutamate receptors in human NT2 neurons

Human NT2-N neurons derived from retinoic acid treatment of the NTera 2 cell line were used to determine the consequences of ionotropic glutamate receptor (iGluR) hyperstimulation and possible modulatory role(s) exerted by metabotropic glutamate receptor (mGluR) activation. We found that NT2-N neurons express the NR1 subunit of N-methyl-D-aspartate (NMDA) iGluRs and mRNA encoding the 1a isoform of mGluRs. A 15 min pulse with 100 microM NMDA induced an increase in the levels of tau proteins in NT2-N cells. This effect was prevented by incubating NT2-N neurons in the presence of the mGluR agonist (1 S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD). This phenomenon was related, in terms of doses and time, with the observed 1S,3R-ACPD-mediated protection against NMDA-induced NT2-N cell death. Our findings suggest that iGluRs and mGluRs might participate in the control of human neuron viability by differentially affecting the expression of tau proteins.