Browsing by Author "Morris, Cameron W."

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    The association of spinophilin with disks large-associated protein 3 (SAPAP3) is regulated by metabotropic glutamate receptor (mGluR) 5
    (Elsevier, 2018) Morris, Cameron W.; Watkins, Darryl S.; Salek, Asma B.; Edler, Michael C.; Baucum, Anthony J., II; Biology, School of Science
    Spinophilin is the most abundant protein phosphatase 1 targeting protein in the postsynaptic density of dendritic spines. Spinophilin associates with myriad synaptic proteins to regulate normal synaptic communication; however, the full complement of spinophilin interacting proteins and mechanisms regulating spinophilin interactions are unclear. Here we validate an association between spinophilin and the scaffolding protein, disks large-associated protein 3 (SAP90/PSD-95 associated protein 3; SAPAP3). Loss of SAPAP3 leads to obsessive-compulsive disorder (OCD)-like behaviors due to alterations in metabotropic glutamate receptor (mGluR) signaling. Here we report that spinophilin associates with SAPAP3 in the brain and in a heterologous cell system. Moreover, we have found that expression or activation of group I mGluRs along with activation of the mGluR-dependent kinase, protein kinase C β, enhances this interaction. Functionally, global loss of spinophilin attenuates amphetamine-induced hyperlocomotion, a striatal behavior associated with dopamine dysregulation and OCD. Together, these data delineate a novel link between mGluR signaling, spinophilin, and SAPAP3 in striatal pathophysiology.
  • Thumbnail Image
    Item
    Mechanisms and Consequences of Dopamine Depletion-Induced Attenuation of the Spinophilin/Neurofilament Medium Interaction
    (Hindawi, 2017) Hiday, Andrew C.; Edler, Michael C.; Salek, Asma B.; Morris, Cameron W.; Thang, Morrent; Rentz, Tyler J.; Rose, Kristie L.; Jones, Lisa M.; Baucum, Anthony J., II; Biology, School of Science
    Signaling changes that occur in the striatum following the loss of dopamine neurons in the Parkinson disease (PD) are poorly understood. While increases in the activity of kinases and decreases in the activity of phosphatases have been observed, the specific consequences of these changes are less well understood. Phosphatases, such as protein phosphatase 1 (PP1), are highly promiscuous and obtain substrate selectivity via targeting proteins. Spinophilin is the major PP1-targeting protein enriched in the postsynaptic density of striatal dendritic spines. Spinophilin association with PP1 is increased concurrent with decreases in PP1 activity in an animal model of PD. Using proteomic-based approaches, we observed dopamine depletion-induced decreases in spinophilin binding to multiple protein classes in the striatum. Specifically, there was a decrease in the association of spinophilin with neurofilament medium (NF-M) in dopamine-depleted striatum. Using a heterologous cell line, we determined that spinophilin binding to NF-M required overexpression of the catalytic subunit of protein kinase A and was decreased by cyclin-dependent protein kinase 5. Functionally, we demonstrate that spinophilin can decrease NF-M phosphorylation. Our data determine mechanisms that regulate, and putative consequences of, pathological changes in the association of spinophilin with NF-M that are observed in animal models of PD.
  • Thumbnail Image
    Item
    Mechanisms Regulating the Association of Protein Phosphatase 1 with Spinophilin and Neurabin
    (American Chemical Society, 2018-11-21) Edler, Michael C.; Salek, Asma B.; Watkins, Darryl S.; Kaur, Harjot; Morris, Cameron W.; Yamamoto, Bryan K.; Baucum, Anthony J., II; Biology, School of Science
    Protein phosphorylation is a key mediator of signal transduction, allowing for dynamic regulation of substrate activity. Whereas protein kinases obtain substrate specificity by targeting specific amino acid sequences, serine/threonine phosphatase catalytic subunits are much more promiscuous in their ability to dephosphorylate substrates. To obtain substrate specificity, serine/threonine phosphatases utilize targeting proteins to regulate phosphatase subcellular localization and catalytic activity. Spinophilin and its homologue neurabin are two of the most abundant dendritic spine-localized protein phosphatase 1 (PP1) targeting proteins. The association between spinophilin and PP1 is increased in the striatum of animal models of Parkinson's disease (PD). However, mechanisms that regulate the association of spinophilin and neurabin with PP1 are unclear. Here, we report that the association between spinophilin and PP1α or PP1γ1 was increased by CDK5 expression and activation in a heterologous cell system. This increased association is at least partially due to phosphorylation of PP1. Conversely, CDK5 expression and activation decreased the association of PP1 with neurabin. As with dopamine depletion, methamphetamine (METH) abuse causes persistent alterations in dopamine signaling which influence striatal medium spiny neuron function and biochemistry. Moreover, both METH toxicity and dopamine depletion are associated with deficits in motor control and motor learning. Pathologically, we observed a decreased association of spinophilin with PP1 in rat striatum evaluated one month following a binge METH paradigm. Behaviorally, we found that loss of spinophilin recapitulates rotarod pathology previously observed in dopamine-depleted and METH-treated animals. Together, these data have implications in multiple disease states associated with altered dopamine signaling such as PD and psychostimulant drug abuse and delineate a novel mechanism by which PP1 interactions with spinophilin and neurabin may be differentially regulated.
  • Thumbnail Image
    Item
    Prenatal methadone exposure disrupts behavioral development and alters motor neuron intrinsic properties and local circuitry
    (eLife Sciences, 2021-03-16) Grecco, Gregory G.; Mork, Briana E.; Huang, Jui-Yen; Metzger, Corinne E.; Haggerty, David L.; Reeves, Kaitlin C.; Gao, Yong; Hoffman, Hunter; Katner, Simon N.; Masters, Andrea R.; Morris, Cameron W.; Newell, Erin A.; Engleman, Eric A.; Baucum, Anthony J.; Kim, Jiuen; Yamamoto, Bryan K.; Allen, Matthew R.; Wu, Yu-Chien; Lu, Hui-Chen; Sheets, Patrick L.; Atwood, Brady K.; Pharmacology and Toxicology, School of Medicine
    Despite the rising prevalence of methadone treatment in pregnant women with opioid use disorder, the effects of methadone on neurobehavioral development remain unclear. We developed a translational mouse model of prenatal methadone exposure (PME) that resembles the typical pattern of opioid use by pregnant women who first use oxycodone then switch to methadone maintenance pharmacotherapy, and subsequently become pregnant while maintained on methadone. We investigated the effects of PME on physical development, sensorimotor behavior, and motor neuron properties using a multidisciplinary approach of physical, biochemical, and behavioral assessments along with brain slice electrophysiology and in vivo magnetic resonance imaging. Methadone accumulated in the placenta and fetal brain, but methadone levels in offspring dropped rapidly at birth which was associated with symptoms and behaviors consistent with neonatal opioid withdrawal. PME produced substantial impairments in offspring physical growth, activity in an open field, and sensorimotor milestone acquisition. Furthermore, these behavioral alterations were associated with reduced neuronal density in the motor cortex and a disruption in motor neuron intrinsic properties and local circuit connectivity. The present study adds to the limited body of work examining PME by providing a comprehensive, translationally relevant characterization of how PME disrupts offspring physical and neurobehavioral development.
  • Thumbnail Image
    Item
    Spinophilin Cell Type-Specifically Mediates Metabotrophic Glutamate Receptor 5-dependent Excessive Grooming
    (2022-09) Morris, Cameron W.; Truitt, William; Atwood, Brady; Baucum, Anthony J., II; Ma, Yao-Ying; McKinzie, David
    Compulsive and repetitive behaviors in obsessive-compulsive spectrum disorders (OCSDs) are associated with perturbations in the sensorimotor striatum. Repetitive behaviors are associated with cell type-specific adaptations in striatal direct- and indirect-pathway medium spiny neurons (dMSNs and iMSNs, respectively). Furthermore, preclinical models for understanding OCSDs, such as constitutive knockout of disks large associated protein 3 (SAPAP3), suggest repetitive motor dysfunction, such as excessive grooming, is associated with increased metabotropic glutamate receptor 5 (mGluR5) activity that increases dMSN function relative to iMSNs in the sensorimotor striatum. However, MSN subtype-specific signaling mechanisms that mediate mGluR5-dependent adaptations underlying excessive grooming are not fully understood. Reversible phosphorylation of mGluR5’s C-terminal domain is one mechanism to regulate mGluR5 signaling, however, unlike kinases, promiscuous phosphatases require targeting proteins to shuttle them into contact with their targets. Therefore, phosphatase targeting proteins may be intimately involved in mediating mGluR5-dependent striatal adaptions underlying repetitive behaviors, such as excessive grooming in SAPAP3 deficient mice. Spinophilin, a major striatal postsynaptic phosphatase targeting protein, regulates striatal function, mGluR5 signaling, and forms a protein-protein interaction with SAPAP3 that is increased by mGluR5 co-expression. Therefore, we hypothesized that spinophilin expression in striatal medium spiny neurons mediates mGluR5-dependent excessive grooming. To test this, we used a novel conditional spinophilin mouse line combined with functional, behavioral, and molecular approaches to elucidate spinophilin's MSN subtype-specific contributions to rodent excessive grooming behavior associated with increased mGluR5 function. We found that loss of spinophilin in either MSN subtype abrogated plasticity in the sensorimotor striatum associated with increased mGluR5 function and decreased two models of excessive grooming associated with increased mGluR5 function—SAPAP3 deficient mice and global administration of a mGluR5-specific positive allosteric modulator (VU0360172). Additionally, we found that spinophilin’s protein interaction with mGluR5 correlates with grooming behavior and loss of spinophilin shifts mGluR5 interactions from lipid-raft associated proteins toward postsynaptic density proteins implicated in psychiatric disorders. Collectively, these results identify spinophilin as a novel striatal signaling hub molecule in MSNs that MSN subtype-specifically mediates striatal adaptations associated with repetitive motor dysfunction in psychiatric disorders.
  • Thumbnail Image
    Item
    Spinophilin Limits Metabotropic Glutamate Receptor 5 Scaffolding to the Postsynaptic Density and Cell Type Specifically Mediates Excessive Grooming
    (Elsevier, 2023) Morris, Cameron W.; Watkins, Darryl S.; Shah, Nikhil R.; Pennington, Taylor; Hens, Basant; Qi, Guihong; Doud, Emma H.; Mosley, Amber L.; Atwood, Brady K.; Baucum, Anthony J., II; Pharmacology and Toxicology, School of Medicine
    Background: Grooming dysfunction is a hallmark of the obsessive-compulsive spectrum disorder trichotillomania. Numerous preclinical studies have utilized SAPAP3-deficient mice for understanding the neurobiology of repetitive grooming, suggesting that excessive grooming is caused by increased metabotropic glutamate receptor 5 (mGluR5) activity in striatal direct- and indirect-pathway medium spiny neurons (MSNs). However, the MSN subtype-specific signaling mechanisms that mediate mGluR5-dependent adaptations underlying excessive grooming are not fully understood. Here, we investigated the MSN subtype-specific roles of the striatal signaling hub protein spinophilin in mediating repetitive motor dysfunction associated with mGluR5 function. Methods: Quantitative proteomics and immunoblotting were utilized to identify how spinophilin impacts mGluR5 phosphorylation and protein interaction changes. Plasticity and repetitive motor dysfunction associated with mGluR5 action were measured using our novel conditional spinophilin mouse model in which spinophilin was knocked out from striatal direct-pathway MSNs and/or indirect-pathway MSNs. Results: Loss of spinophilin only in indirect-pathway MSNs decreased performance of a novel motor repertoire, but loss of spinophilin in either MSN subtype abrogated striatal plasticity associated with mGluR5 function and prevented excessive grooming caused by SAPAP3 knockout mice or treatment with the mGluR5-specific positive allosteric modulator VU0360172 without impacting locomotion-relevant behavior. Biochemically, we determined that the spinophilin-mGluR5 interaction correlates with grooming behavior and that loss of spinophilin shifts mGluR5 interactions from lipid raft-associated proteins toward postsynaptic density proteins implicated in psychiatric disorders. Conclusions: These results identify spinophilin as a novel striatal signaling hub molecule in MSNs that cell subtype specifically mediates behavioral, functional, and molecular adaptations associated with repetitive motor dysfunction in psychiatric disorders.