Elsevier

Neuroscience

Volume 140, Issue 3, 2006, Pages 897-911
Neuroscience

Molecular neuroscience
Distinct roles for spinophilin and neurabin in dopamine-mediated plasticity

https://doi.org/10.1016/j.neuroscience.2006.02.067Get rights and content

Abstract

Protein phosphatase 1 plays a major role in the governance of excitatory synaptic activity, and is subject to control via the neuromodulatory actions of dopamine. Mechanisms involved in regulating protein phosphatase 1 activity include interactions with the structurally related cytoskeletal elements spinophilin and neurabin, synaptic scaffolding proteins that are highly enriched in dendritic spines. The requirement for these proteins in dopamine-related neuromodulation was tested using knockout mice. Dopamine D1-mediated regulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor activity was deficient in both striatal and prefrontal cortical neurons from neurabin knockout mice; in spinophilin knockout mice this deficit was manifest only in striatal neurons. At corticostriatal synapses long-term potentiation was deficient in neurabin knockout mice, but not in spinophilin knockout mice, and was rescued by a D1 receptor agonist. In contrast, long-term depression was deficient in spinophilin knockout mice but not in neurabin knockout mice, and was rescued by D2 receptor activation. Spontaneous excitatory post-synaptic current frequency was increased in neurabin knockout mice, but not in spinophilin knockout mice, and this effect was normalized by D2 receptor agonist application. Both knockout strains displayed increased induction of GluR1 Ser845 phosphorylation in response to D1 receptor stimulation in slices, and also displayed enhanced locomotor activation in response to cocaine administration. These effects could be dissociated from cocaine reward, which was enhanced only in spinophilin knockout mice, and was accompanied by increased immediate early gene induction. These data establish a requirement for synaptic scaffolding in dopamine-mediated responses, and further indicate that spinophilin and neurabin play distinct roles in dopaminergic signal transduction and psychostimulant response.

Section snippets

Gene targeting and strain development

Generation of the spinophilin KO was described previously (Feng et al., 2000). Mutation of the neurabin gene was performed essentially using the methodology of Wattler et al. (1999). Using a PCR strategy with primers derived from a 5′ EST, four overlapping genomic clones spanning 14 kb were isolated from a lambda KOS library. Each genomic insert was flanked by the negative selection marker, tk, and contained bacterial and yeast origins of replication, a bacterial bla resistance marker, the

Results

The neurabin gene was disrupted in embryonic stem cells using a replacement targeting vector that results in deletion of the first coding exon, producing a null allele. Western blot analysis of total brain homogenate using an antibody raised against the neurabin C-terminus (Muly et al., 2004a) confirmed a complete loss of neurabin protein expression (Fig. 1). Examination of PP1 levels in striatal extracts revealed a significant reduction (∼30%) in expression level in both neurabin KO mice and

Discussion

We have tested the requirement for the structurally similar synaptic scaffolding proteins, spinophilin and neurabin, in dopamine-mediated neuromodulation in KO mouse strains. We found altered responses in all paradigms examined, and the two strains differed strikingly in a number of ways. However, in both spinophilin and neurabin KO mice, striatal levels of PP1 were reduced, which is consistent with the proposed functional roles of these scaffolds in PP1 control. Presumably, a cellular

Acknowledgments

This research was supported by fellowships from NARSAD and the Tourette Syndrome Association (PBA), National Institutes of Health grants MH40899 and DA1044 (P.G.), and EEC grant “SYNSCAFF” (P.C.).

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    Present address: Intra-Cellular Therapies, Inc., 3960 Broadway, New York, NY 10021, USA.

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