Here, we show that disruption of N-ethylmaleimide-sensitive fusion protein- (NSF-) GluR2 interaction by infusion into cultured hippocampal neurons of a blocking peptide (pep2m) caused a rapid decrease in the frequency but no change in the amplitude of AMPA receptor-mediated miniature excitatory postsynaptic currents (mEPSCs). N-methyl-D-aspartate (NMDA) receptor-mediated mEPSCs were not changed. Viral expression of pep2m reduced the surface expression of alpha-amino-3-hydroxy-5-methyl-isoxazolepropionate (AMPA) receptors, whereas NMDA receptor surface expression in the same living cells was unchanged. In permeabilized neurons, the total amount of GluR2 immunoreactivity was unchanged, and a punctate distribution of GluR2 was observed throughout the dendritic tree. These data suggest that the NSF-GluR2 interaction is required for the surface expression of GluR2-containing AMPA receptors and that disruption of the interaction leads to the functional elimination of AMPA receptors at synapses.

AMPA receptors (AMPARs) are dynamically regulated at synapses, but the time course and location of their exocytosis and endocytosis are not known. Therefore, we have used ecliptic pHluorin-tagged glutamate receptor 2 to visualize changes in AMPAR surface expression in real time. We show that synaptic and extrasynaptic AMPARs respond very differently to NMDA receptor activation; there is a rapid internalization of extrasynaptic AMPARs that precedes the delayed removal of synaptic AMPARs.

MicroRNAs are known to regulate developmental processes but their mechanism of regulation remains largely uncharacterized. We show the transcription factor Twist-1 drives the expression of a 7.9-kb noncoding RNA transcript (from the Dynamin-3 gene intron) that encodes a miR-199a and miR-214 cluster. We also show that knocking down Twist-1 with shRNAs decreased miR-199a/214 levels and that Twist-1 bound an E-Box promoter motif to developmentally regulate the expression of these miRNAs. The expression of HIF-1 (known to mediate Twist-1 transcription), miR-199a and miR-214 was maximal at E12.5 and the miRNAs were expressed specifically in mouse cerebellum, midbrain, nasal process and fore- and hindlimb buds. This study shows the expression of the miR199a/214 cluster is controlled by Twist-1 via an E-Box promoter element and supports a role for these miRNAs as novel intermediates in the pathways controlling the development of specific neural cell populations.

No abstract