Increased expression of dysbindin-1A leads to a selective deficit in NMDA receptor signaling in the hippocampus
ABSTRACT The effects of the major schizophrenia susceptibility gene disease DTNBP1 on disease risk are likely to be mediated through changes in expression level of the gene product, dysbindin-1. How such changes might influence pathogenesis is, however, unclear. One possible mechanism is suggested by recent work establishing a link between altered dysbindin-1 expression and changes in surface levels of N-methyl-d-aspartate receptors (NMDAR), although neither the precise nature of this relationship, nor the mechanism underlying it, are understood. Using organotypic slices of rat hippocampus, we show that increased expression of dysbindin-1A in pyramidal neurons causes a severe and selective hypofunction of NMDARs and blocks induction of LTP. Cell surface, but not cytoplasmic, expression of the NR1 subunit of the NMDAR is decreased, suggesting dysregulation of NMDAR trafficking and, consistent with this, pharmacological inhibition of clathrin-dependent endocytosis is sufficient to reverse the deficit in NMDAR signaling. These results support the idea that the level of the NMDAR at the plasma membrane is modulated by changes in dysbindin-1 expression and offer further insight into the role of dysbindin-1 at an important cellular pathway implicated in schizophrenia.
SourceAvailable from: Wei Li[Show abstract] [Hide abstract]
ABSTRACT: DTNBP1 (dystrobrevin-binding protein 1) which encodes dysbindin-1 is one of the leading susceptibility genes for schizophrenia. Both dysbindin-1B and 1C isoforms are decreased but the 1A isoform is unchanged in schizophrenic hippocampal formation, suggesting dysbindin-1 isoforms may have distinct roles in schizophrenia. We found that mouse dysbindin-1C, but not 1A, is localized in the hilar glutamatergic mossy cells of the dentate gyrus. The maturation rate of newborn neurons in sandy (sdy) mice, in which both dysbindin-1A and 1C are deleted, is significantly delayed when compared with that in wild-type mice, or with that in muted (mu) mice in which dysbindin-1A is destabilized but 1C is unaltered. Dysbindin-1C deficiency leads to a decrease in mossy cells, which causes the delayed maturation of newborn neurons. This suggests that dysbindin-1C, rather than 1A, regulates adult hippocampal neurogenesis in a non-cell autonomous manner.Journal of Biological Chemistry 08/2014; 289(42). DOI:10.1074/jbc.M114.590927 · 4.60 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Glutamatergic signaling through N-methyl-D-aspartate receptors (NMDARs) is important for neuronal development and plasticity and is often dysregulated in psychiatric disorders. Mice mutant for the transcription factor Sp4 have reduced levels of NMDAR subunit 1 (NR1) protein, but not mRNA, and exhibit behavioral and memory deficits (Zhou et al., 2010). In developing cerebellar granule neurons (CGNs), Sp4 controls dendrite patterning (Ramos et al., 2007). Sp4 target genes that regulate dendrite pruning or NR1 levels are not known. Here we report that Sp4 activates transcription of Nervous Wreck 2 (Nwk2; also known as Fchsd1) and, further, that Nwk2, an F-BAR-domain containing protein, mediates Sp4-dependent regulation of dendrite patterning and cell surface expression of NR1. Knockdown of Nwk2 in CGNs increased primary dendrite number, phenocopying Sp4 knockdown, and exogenous expression of Nwk2 in Sp4-depleted neurons rescued dendrite number. We observed that acute Sp4 depletion reduced levels of surface, but not total, NR1, and this was rescued by Nwk2 expression. Furthermore, expression of Nr1 suppressed the increase in dendrite number in Sp4- or Nwk2- depleted neurons. We previously reported that Sp4 protein levels were reduced in cerebellum of subjects with bipolar disorder (BD) (Pinacho et al., 2011). Here we report that Nwk2 mRNA and NR1 protein levels were also reduced in postmortem cerebellum of BD subjects. Our data suggest a role for Sp4-regulated Nwk2 in NMDAR trafficking and identify an Sp4-Nwk2-NMDAR1 pathway that regulates neuronal morphogenesis during development and may be disrupted in bipolar disorder. © 2014 Wiley Periodicals, Inc. Develop Neurobiol, 2014Developmental Neurobiology 01/2015; 75(1). DOI:10.1002/dneu.22212 · 4.19 Impact Factor
Journal of Biological Chemistry 10/2014; 289(42):29060-29072. · 4.60 Impact Factor