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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

Spatial learning and memory in MWM. WT and sdy animals were injected with either vehicle (Veh) or CDPPB (10 mg/kg, ip), (n = 6–7 per genotype/treatment) once a day, for 6 days, 30 min before the first trial of the day in. (A) Escape latency (seconds) during hidden platform location for WT and sdy animals following either vehicle or CDPPB administration. Sdy-vehicle animals have significant deficit in spatial learning compared to WT-vehicle animals on days 5 and 6 (*p < 0.05). CDPPB treatments significantly improved the learning deficit in sdy animals compared to vehicle treated sdy animals (#p < 0.05). (B) Time spent in the target quadrant in the probe test. Vehicle treated sdy mice showed a significant deficit compared to vehicle treated WT mice in the time spent in correct quadrant (**p = 0.002). CDPPB treatment attenuated this spatial memory deficit in sdy mice as no significant differences in the target quadrant preference was observed between sdy and WT CDPPB treated animals. (C) Average annulus crossings during probe trial for all animals. Similar to target quadrant preference, annulus crossings also revealed a significant deficit in spatial memory in sdy mice and its amelioration by CDPPB (**p = 0.0012, vehicle treated sdy mice compared to vehicle treated WT mice; (&p = 0.042, sdy CDPPB vs. sdy vehicle. (D) Visible platform data revealed no significant differences in mean swim speed among experimental groups.
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Figure 7: Spatial learning and memory in MWM. WT and sdy animals were injected with either vehicle (Veh) or CDPPB (10 mg/kg, ip), (n = 6–7 per genotype/treatment) once a day, for 6 days, 30 min before the first trial of the day in. (A) Escape latency (seconds) during hidden platform location for WT and sdy animals following either vehicle or CDPPB administration. Sdy-vehicle animals have significant deficit in spatial learning compared to WT-vehicle animals on days 5 and 6 (*p < 0.05). CDPPB treatments significantly improved the learning deficit in sdy animals compared to vehicle treated sdy animals (#p < 0.05). (B) Time spent in the target quadrant in the probe test. Vehicle treated sdy mice showed a significant deficit compared to vehicle treated WT mice in the time spent in correct quadrant (**p = 0.002). CDPPB treatment attenuated this spatial memory deficit in sdy mice as no significant differences in the target quadrant preference was observed between sdy and WT CDPPB treated animals. (C) Average annulus crossings during probe trial for all animals. Similar to target quadrant preference, annulus crossings also revealed a significant deficit in spatial memory in sdy mice and its amelioration by CDPPB (**p = 0.0012, vehicle treated sdy mice compared to vehicle treated WT mice; (&p = 0.042, sdy CDPPB vs. sdy vehicle. (D) Visible platform data revealed no significant differences in mean swim speed among experimental groups.

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)

Spatial learning and memory in MWM. WT and sdy animals were injected with either vehicle (Veh) or CDPPB (10 mg/kg, ip), (n = 6–7 per genotype/treatment) once a day, for 6 days, 30 min before the first trial of the day in. (A) Escape latency (seconds) during hidden platform location for WT and sdy animals following either vehicle or CDPPB administration. Sdy-vehicle animals have significant deficit in spatial learning compared to WT-vehicle animals on days 5 and 6 (*p < 0.05). CDPPB treatments significantly improved the learning deficit in sdy animals compared to vehicle treated sdy animals (#p < 0.05). (B) Time spent in the target quadrant in the probe test. Vehicle treated sdy mice showed a significant deficit compared to vehicle treated WT mice in the time spent in correct quadrant (**p = 0.002). CDPPB treatment attenuated this spatial memory deficit in sdy mice as no significant differences in the target quadrant preference was observed between sdy and WT CDPPB treated animals. (C) Average annulus crossings during probe trial for all animals. Similar to target quadrant preference, annulus crossings also revealed a significant deficit in spatial memory in sdy mice and its amelioration by CDPPB (**p = 0.0012, vehicle treated sdy mice compared to vehicle treated WT mice; (&p = 0.042, sdy CDPPB vs. sdy vehicle. (D) Visible platform data revealed no significant differences in mean swim speed among experimental groups.
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Figure 7: Spatial learning and memory in MWM. WT and sdy animals were injected with either vehicle (Veh) or CDPPB (10 mg/kg, ip), (n = 6–7 per genotype/treatment) once a day, for 6 days, 30 min before the first trial of the day in. (A) Escape latency (seconds) during hidden platform location for WT and sdy animals following either vehicle or CDPPB administration. Sdy-vehicle animals have significant deficit in spatial learning compared to WT-vehicle animals on days 5 and 6 (*p < 0.05). CDPPB treatments significantly improved the learning deficit in sdy animals compared to vehicle treated sdy animals (#p < 0.05). (B) Time spent in the target quadrant in the probe test. Vehicle treated sdy mice showed a significant deficit compared to vehicle treated WT mice in the time spent in correct quadrant (**p = 0.002). CDPPB treatment attenuated this spatial memory deficit in sdy mice as no significant differences in the target quadrant preference was observed between sdy and WT CDPPB treated animals. (C) Average annulus crossings during probe trial for all animals. Similar to target quadrant preference, annulus crossings also revealed a significant deficit in spatial memory in sdy mice and its amelioration by CDPPB (**p = 0.0012, vehicle treated sdy mice compared to vehicle treated WT mice; (&p = 0.042, sdy CDPPB vs. sdy vehicle. (D) Visible platform data revealed no significant differences in mean swim speed among experimental groups.
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