CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab

Cell Biology of the Neuron: Polarity, Plasticity and Regeneration, Crete 2011
Role of GluN2B in the Synaptic Accumulation of
NMDA Receptors
Joana Ferreira 1 , Kevin She 2 , Amanda Rooyakkers 2 , Ann Marie Craig 2 , Ana
Luísa Carvalho 1
1
Center for Neuroscience and Cell Biology & Department of Life Sciences,
University of Coimbra, 3004-517 Coimbra, Portugal
2
Brain Research Centre & Department of Psychiatry, University of British
Columbia,Vancouver BC, Canada
The N-methyl-D-aspartate receptor (NMDAR) plays a crucial role in shaping the
strength of synaptic connections, which underlies some forms of learning and
memory formation in the central nervous system. This type of ionotropic
glutamate receptors may be formed by multiple combinations of an obligatory
GluN1 subunit with GluN2 (A to D) or GluN3 (A to B) subunits. In the
hippocampus and the neocortex, the major GluN2 subunits are GluN2A and
GluN2B, which are differentially expressed during development. The
contribution of each subunit to the synaptic traffic of NMDARs and therefore for
synaptic plasticity is still controversional.
To better understand the specific contribution of the GluN2 subunits to the
synaptic expression of NMDARs we used neuronal cultures from GluN2A(-/-)
and GluN2B(-/-) mice, and found that, whereas the synaptic expression of
NMDARs is normal in GluN2A(-/-) hippocampal neurons, there is a dramatic
decrease on the number, intensity and area of synaptic GluN1 clusters in
GluN2B(-/-) hippocampal neurons, when compared with GluN2B (+/+) neurons.
We also found that chronic activity blockade, which increases the synaptic
clustering of NMDA receptors in GluN2B(+/+) neurons, does not have an effect
on GluN2B (-/-) neurons. Furthermore, in cortical GluN2B (-/-) neurons we
observed a significant decrease of GluN1 and GluN2A protein expression levels,
although no changes on mRNA relative levels were detected by real-time PCR.
We assayed the total surface expression of NMDARs by biotinylation assays and
observed that the dramatic effect observed on the total levels of NMDARs on
GluN2B (-/-) neurons reflects on the cell surface levels of these proteins. Taken
together, these results suggest the GluN2B-containing NMDAR may be
responsible for organizing a synaptic scaffold required for synaptic delivery
and/or stabilization of NMDARs.
This study is supported by FCT, Portugal (PTDC/BIA-BCM/71789/2006 and
PTDC/SAU-NEU/099440/2008).
Presented by: Ferreira, Joana Poster No 035
Green Session
117