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Loss of dysbindin-1, a risk gene for schizophrenia, leads to impaired group 1 metabotropic glutamate receptor function in mice.

Bhardwaj SK, Ryan RT, Wong TP, Srivastava LK - Front Behav Neurosci (2015)

Bottom Line: This mGluR-ERK1/2 deficit occurred in the absence of significant changes in protein levels of the two members of the mGluRI family (i.e., mGluR1 and mGluR5) or in another mGluRI signaling pathway, i.e., protein kinase C (PKC).Aberrant mGluRI-ERK1/2 signaling affected hippocampal synaptic plasticity in the sdy mutants as DHPG-induced long-term depression (LTD) at CA1 excitatory synapses was significantly reduced.Taken together, our data suggest a novel role of dysbindin-1 in regulating mGluRI functions.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Integrated Programme in Neuroscience, Douglas Mental Health University Institute, McGill University Montreal, QC, Canada.

ABSTRACT
The expression of dysbindin-1, a protein coded by the risk gene dtnbp1, is reduced in the brains of schizophrenia patients. Evidence indicates a role of dysbindin-1 in dopaminergic and glutamatergic transmission. Glutamatergic transmission and plasticity at excitatory synapses is critically regulated by G-protein coupled metabotropic glutamate receptor (mGluR) family members, that have been implicated in schizophrenia. Here, we report a role of dysbindin-1 in hippocampal group 1 mGluR (mGluRI) function in mice. In hippocampal synaptoneurosomal preparations from sandy (sdy) mice, that have a loss of function mutation in dysbindin-1 gene, we observed a striking reduction in mGluRI agonist [(S)-3, 5-dihydroxyphenylglycine] (DHPG)-induced phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2). This mGluR-ERK1/2 deficit occurred in the absence of significant changes in protein levels of the two members of the mGluRI family (i.e., mGluR1 and mGluR5) or in another mGluRI signaling pathway, i.e., protein kinase C (PKC). Aberrant mGluRI-ERK1/2 signaling affected hippocampal synaptic plasticity in the sdy mutants as DHPG-induced long-term depression (LTD) at CA1 excitatory synapses was significantly reduced. Behavioral data suggest that the mGluRI hypofunction may underlie some of the cognitive abnormalities described in sdy mice as the administration of CDPPB (3-cyano-N-(1, 3-diphenyl-1H-pyrazol-5-yl benzamide), a positive allosteric modulator of mGluR5, rescued short-term object recognition and spatial learning and memory deficits in these mice. Taken together, our data suggest a novel role of dysbindin-1 in regulating mGluRI functions.

No MeSH data available.


Related in: MedlinePlus

Impaired ERK1/2 activation by mGluRI stimulation is observed rapidly at both sub-saturating (5 μM) and saturating (50 μM) concentration of mGluRI agonist S-DHPG. (A) shows the representative Western blot signals of p-ERK1/2, total (t)-ERK 1/2 and β-actin. (B) shows the histogram of ROD of mean ± SEM (n = 6 per genotype) of the normalized p-ERK1/2.
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Figure 3: Impaired ERK1/2 activation by mGluRI stimulation is observed rapidly at both sub-saturating (5 μM) and saturating (50 μM) concentration of mGluRI agonist S-DHPG. (A) shows the representative Western blot signals of p-ERK1/2, total (t)-ERK 1/2 and β-actin. (B) shows the histogram of ROD of mean ± SEM (n = 6 per genotype) of the normalized p-ERK1/2.

Mentions: The levels of total and DHPG-activated ERK1/2 and PKC were measured in hippocampal synaptoneurosomal preparations. Figure 2A shows the representative Western blots and analyses of total and phospho ERK1/2 levels in WT and sdy mice. A two-way ANOVA showed no significant difference in the levels of total ERK1/2 between WT and sdy animals either at the basal level (i.e., vehicle) or after DHPG incubation (genotype: F(1,24) = 0.0057, p = 0.981; DHPG treatment: F(1,24) = 0.099, p = 0.756; genotype × DHPG interaction: F(1,24) = 0.042, p = 0.839) (Figure 2B). However, analysis of P-ERK1/2 data showed significant main effects of genotype (F(1,24) = 34.13, p = 0.0001), DHPG treatment (F(1,24) = 18.60, p = 0.0002) and genotype × DHPG interaction (F(1,24) = 22.22, p = 0.001) (Figure 2C). As expected, DHPG induced significant increase in P-ERK 1/2 in WT synaptoneurosomes; however, DHPG-induced ERK1/2 phosphorylation was markedly attenuated in the sdy animals. Impaired ERK1/2 phosphorylation in sdy synaptoneurosomes was seen rapidly. For example, the difference in p-ERK1/2 between WT and sdy animals is observed as early as 1 min after DHPG application and persisted when saturating concentrations of DHPG (50 μM) were used. A two-way ANOVA of the data revealed a significant effect of genotype (F(1,20) = 30.66, p = 0.0001), DHPG concentration (F(4,20) = 7.47, p = 0.0001) and genotype × DHPG interaction (F(4,20) = 2.66, p = 0.042) (Figure 3). Post hoc test showed that ERK1/2 phosphorylation in Sdy mice increased at 50 μM DHPG compared to 5 μM (p = 0.046) suggesting that increasing the concentration of DHPG may overcome ERK1/2 deficits in sdy mice. In order to find out if mGluRI signaling deficit in sdy mice is specific to ERK1/2 pathway, we measured the level of phospho-PKC in synaptoneurosomes incubated with DHPG. The data showed a significant effect of DHPG treatment on PKC phosphorylation (F(1,16) = 19.66, p = 0.0004); however, no significant effect of the genotype (F(1,16) = 0.39, p = 0.539) or genotype × DHPG interaction (F(1,16) = 0.63, p = 0.437) was observed (Figure 4). In order to investigate if deficits in ERK1/2 phosphorylation in sdy animals are ameliorated by mGluR5 PAM CDPPB, synaptoneurosomes were incubated with Vehicle, DHPG (5 μM), CDPPB (5 μM) or CDPPB (5 μM) + DHPG (5 μM). Two way ANOVA of p-ERK1/2 data shows a significant effects of genotype (F(1,24) = 12.08, p = 0.002), drug treatment (F(3,24) = 16.93, p = 0.0001) and genotype × drug interaction (F(3,24) = 3.89, p = 0.021). Post hoc showed significantly increased DHPG-induced p-ERK1/2 in Sdy synaptoneurosome preincubated with CDPPB. This effect of CDPPB was not observed in the WT synaptoneurosomes (Figure 8).


Loss of dysbindin-1, a risk gene for schizophrenia, leads to impaired group 1 metabotropic glutamate receptor function in mice.

Bhardwaj SK, Ryan RT, Wong TP, Srivastava LK - Front Behav Neurosci (2015)

Impaired ERK1/2 activation by mGluRI stimulation is observed rapidly at both sub-saturating (5 μM) and saturating (50 μM) concentration of mGluRI agonist S-DHPG. (A) shows the representative Western blot signals of p-ERK1/2, total (t)-ERK 1/2 and β-actin. (B) shows the histogram of ROD of mean ± SEM (n = 6 per genotype) of the normalized p-ERK1/2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4374471&req=5

Figure 3: Impaired ERK1/2 activation by mGluRI stimulation is observed rapidly at both sub-saturating (5 μM) and saturating (50 μM) concentration of mGluRI agonist S-DHPG. (A) shows the representative Western blot signals of p-ERK1/2, total (t)-ERK 1/2 and β-actin. (B) shows the histogram of ROD of mean ± SEM (n = 6 per genotype) of the normalized p-ERK1/2.
Mentions: The levels of total and DHPG-activated ERK1/2 and PKC were measured in hippocampal synaptoneurosomal preparations. Figure 2A shows the representative Western blots and analyses of total and phospho ERK1/2 levels in WT and sdy mice. A two-way ANOVA showed no significant difference in the levels of total ERK1/2 between WT and sdy animals either at the basal level (i.e., vehicle) or after DHPG incubation (genotype: F(1,24) = 0.0057, p = 0.981; DHPG treatment: F(1,24) = 0.099, p = 0.756; genotype × DHPG interaction: F(1,24) = 0.042, p = 0.839) (Figure 2B). However, analysis of P-ERK1/2 data showed significant main effects of genotype (F(1,24) = 34.13, p = 0.0001), DHPG treatment (F(1,24) = 18.60, p = 0.0002) and genotype × DHPG interaction (F(1,24) = 22.22, p = 0.001) (Figure 2C). As expected, DHPG induced significant increase in P-ERK 1/2 in WT synaptoneurosomes; however, DHPG-induced ERK1/2 phosphorylation was markedly attenuated in the sdy animals. Impaired ERK1/2 phosphorylation in sdy synaptoneurosomes was seen rapidly. For example, the difference in p-ERK1/2 between WT and sdy animals is observed as early as 1 min after DHPG application and persisted when saturating concentrations of DHPG (50 μM) were used. A two-way ANOVA of the data revealed a significant effect of genotype (F(1,20) = 30.66, p = 0.0001), DHPG concentration (F(4,20) = 7.47, p = 0.0001) and genotype × DHPG interaction (F(4,20) = 2.66, p = 0.042) (Figure 3). Post hoc test showed that ERK1/2 phosphorylation in Sdy mice increased at 50 μM DHPG compared to 5 μM (p = 0.046) suggesting that increasing the concentration of DHPG may overcome ERK1/2 deficits in sdy mice. In order to find out if mGluRI signaling deficit in sdy mice is specific to ERK1/2 pathway, we measured the level of phospho-PKC in synaptoneurosomes incubated with DHPG. The data showed a significant effect of DHPG treatment on PKC phosphorylation (F(1,16) = 19.66, p = 0.0004); however, no significant effect of the genotype (F(1,16) = 0.39, p = 0.539) or genotype × DHPG interaction (F(1,16) = 0.63, p = 0.437) was observed (Figure 4). In order to investigate if deficits in ERK1/2 phosphorylation in sdy animals are ameliorated by mGluR5 PAM CDPPB, synaptoneurosomes were incubated with Vehicle, DHPG (5 μM), CDPPB (5 μM) or CDPPB (5 μM) + DHPG (5 μM). Two way ANOVA of p-ERK1/2 data shows a significant effects of genotype (F(1,24) = 12.08, p = 0.002), drug treatment (F(3,24) = 16.93, p = 0.0001) and genotype × drug interaction (F(3,24) = 3.89, p = 0.021). Post hoc showed significantly increased DHPG-induced p-ERK1/2 in Sdy synaptoneurosome preincubated with CDPPB. This effect of CDPPB was not observed in the WT synaptoneurosomes (Figure 8).

Bottom Line: This mGluR-ERK1/2 deficit occurred in the absence of significant changes in protein levels of the two members of the mGluRI family (i.e., mGluR1 and mGluR5) or in another mGluRI signaling pathway, i.e., protein kinase C (PKC).Aberrant mGluRI-ERK1/2 signaling affected hippocampal synaptic plasticity in the sdy mutants as DHPG-induced long-term depression (LTD) at CA1 excitatory synapses was significantly reduced.Taken together, our data suggest a novel role of dysbindin-1 in regulating mGluRI functions.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Integrated Programme in Neuroscience, Douglas Mental Health University Institute, McGill University Montreal, QC, Canada.

ABSTRACT
The expression of dysbindin-1, a protein coded by the risk gene dtnbp1, is reduced in the brains of schizophrenia patients. Evidence indicates a role of dysbindin-1 in dopaminergic and glutamatergic transmission. Glutamatergic transmission and plasticity at excitatory synapses is critically regulated by G-protein coupled metabotropic glutamate receptor (mGluR) family members, that have been implicated in schizophrenia. Here, we report a role of dysbindin-1 in hippocampal group 1 mGluR (mGluRI) function in mice. In hippocampal synaptoneurosomal preparations from sandy (sdy) mice, that have a loss of function mutation in dysbindin-1 gene, we observed a striking reduction in mGluRI agonist [(S)-3, 5-dihydroxyphenylglycine] (DHPG)-induced phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2). This mGluR-ERK1/2 deficit occurred in the absence of significant changes in protein levels of the two members of the mGluRI family (i.e., mGluR1 and mGluR5) or in another mGluRI signaling pathway, i.e., protein kinase C (PKC). Aberrant mGluRI-ERK1/2 signaling affected hippocampal synaptic plasticity in the sdy mutants as DHPG-induced long-term depression (LTD) at CA1 excitatory synapses was significantly reduced. Behavioral data suggest that the mGluRI hypofunction may underlie some of the cognitive abnormalities described in sdy mice as the administration of CDPPB (3-cyano-N-(1, 3-diphenyl-1H-pyrazol-5-yl benzamide), a positive allosteric modulator of mGluR5, rescued short-term object recognition and spatial learning and memory deficits in these mice. Taken together, our data suggest a novel role of dysbindin-1 in regulating mGluRI functions.

No MeSH data available.


Related in: MedlinePlus