Session Title: Neurodevelopment and Neurodegeneration
Presentation Date: Friday, March 14 – Saturday, March 15, 2009
ROLE OF N-METHYL-D-ASPARTATE RECEPTORS IN ENDOPLASMIC RETICULUM STRESS INDUCED BY AMYLOID-BETA OLIGOMERS
R.O. Costa1, P.N. Lacor2, I.L. Ferreira1, A.C. Rego1, W.L. Klein2, C. Pereira1
1Center for Neuroscience and Cell Biology, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Coimbra, Portugal, 2Northwestern University, NBP, Evanston, United States
A number of studies have revealed elevated levels of endoplasmic reticulum (ER) stress markers in the brain of Alzheimer's disease (AD) patients. In our investigations of possible mechanisms, we have demonstrated that ER-stress is induced in cultured neurons by oligomeric forms of the AD-associated amyloid-beta (Aβ) peptide. Because soluble Aβ-oligomers (or ADDLs) have been shown to target and activate N-Methyl-D-Aspartate receptors (NMDA-R) in mature hippocampal neurons, we hypothesize that ADDLs can trigger ER stress by an NMDA-R-dependent mechanism. The aim of this work is to investigate this hypothesis and to discriminate the role of the NMDA-R subunits NR2A and NR2B in this process.
As our model, we are using primary cultures of mature hippocampal neurons (DIV20) treated with increasing concentrations of Aβ-oligomers/ADDLs or with thapsigargin (classical ER stressor), for 1-6 hrs. As ER-stress markers, protein levels of Grp78, caspase-12,-11, and -5, P-PERK, P-IRE1α and ATF6α are evaluated, as well as the induction of the transcription factor CHOP. Additionally, we are investigating ER calcium homeostasis. The involvement of NMDA-R subunits (NR2A and NR2B) in ADDLs-induced ER stress are being investigated in cultured hippocampal neurons with similar expression levels of NR2A/B. Results will be correlated with membrane surface expression levels of both NMDA-R subunits.
By doing this, we will be able to demonstrate that ADDLs impair NR2A and/or NR2B subunits of NMDA-R leading to ER-stress, thus contributing to elucidate the molecular mechanisms involved in neuronal cell death triggered by soluble Aβ-peptide.
Supported by Fundação para a Ciência e a Tecnologia: Project nºPTDC/SAU-NEU/71675/2006.