Biology subjects

Baucum, A. J.

Publications and source records attributed to Baucum, A. J..

8 recordsLinked to original sources

bioRxiv2025

Proteomic Characterization of Striatal Neurabin Interactome and its Sex Specific Impact on Motor Behavior.

The striatum serves as the primary input nucleus of the basal ganglia. Reversible protein phosphorylation in the post synaptic density (PSD) of medium spiny neurons (MSNs) modulates inputs from striatal afferents. The context dependent regulation of PSD protein phosphorylation in direct-pathway medium spiny neurons (dMSNs) and indirect-pathway medium spiny neurons (iMSNs) works to differentially and synergistically impact striatal physiology and the execution of motor programs. An important regulator of PSD protein phosphorylation is protein phosphatase 1 (PP1), which obtains substrate specificity through the action of PP1 targeting proteins. While prior work has demonstrated the global and cell type-specific impact of the PP1 targeting protein, spinophilin, on striatal motor behaviors like the accelerating rotarod task and amphetamine sensitization, the role of its homologue, neurabin, is yet to be elucidated. Proteomics determined that striatal neurabin associates with pre and postsynaptic proteins associated with glutamatergic synapse function. Moreover, we found that global loss of neurabin enhanced rotarod motor learning but had no impact on amphetamine sensitization. Interestingly, using novel conditional neurabin knockout mouse lines, we found that loss of neurabin in dMSNs, but not iMSNs, enhanced performance on the accelerating rotarod task and that these effects were specific for male mice. These data highlight neurabins particular importance to the striatal glutamatergic synapse and uncover a sex and cell type specific role for this synaptic protein in uniquely limiting skill motor learning but not psychomotor sensitization.

neuroscience↗

bioRxiv2025

Striatal spinophilin enhances D2R interaction with cytosolic proteins to mediate persistent D2R agonist-induced locomotor suppression.

Loss of dopamine neurons in Parkinson disease (PD) leads to motor deficits. Dopamine D2 receptor (D2R) agonists treat PD-associated motor deficits by acting on postsynaptic receptors located within the striatum that have been upregulated due dopamine loss. However, mechanisms that contribute to increased D2R activity in PD to enhance D2R function are poorly described. Spinophilin is a protein phosphatase 1 targeting protein that is expressed in postsynaptic dendritic spines and interacts with postsynaptic D2Rs. However, how spinophilin regulates D2R function is unknown. In the current study, we found that genetic knockout of spinophilin limited the suppression of locomotion caused by the D2R agonist, quinpirole. Mechanistically, we found that spinophilin is required for quinpirole-induced increases in the interaction of the D2R with intracellular proteins, suggesting spinophilin mediates agonist-induced D2R internalization. Therefore, our data support future studies targeting the spinophilin/D2R interaction to enhance the efficacy of current PD therapeutics.

neuroscience↗

bioRxiv2025

Proximity labeling and orthogonal nanobody pulldown (ID-oPD) approaches to map the spinophilin interactome uncover a putative role for spinophilin in protein homeostasis.

Spinophilin is a dendritic spine enriched scaffolding and protein phosphatase 1 targeting protein. To detail spinophilin interacting proteins, we created an Ultra-ID and ALFA-tagged spinophilin encoding construct that permits proximity labeling and orthogonal nanobody pulldown (ID-oPD) of spinophilin-associated protein complexes in heterologous cells. We identified 614 specific, and 312 specific and selective, spinophilin interacting proteins in HEK293 cells and validated a subset of these using orthogonal approaches. Many of these proteins are involved in mRNA processing and translation. In the brain, we determined that spinophilin mRNA is highly neuropil localized and that spinophilin may normally function to limit its own expression but promote the expression of other PSD-associated proteins. Overall, our use of an ID-oPD approach uncovers a novel putative role for spinophilin in mRNA translation and synaptic protein expression specifically within dendritic spines.

neuroscience↗

bioRxiv2023

Mechanisms of spinophilin-dependent pancreas dysregulation underlying diabesity

ObjectiveSpinophilin is an F-actin binding and protein phosphatase 1 (PP1) targeting protein that acts as a scaffold of PP1 to its substrates. Spinophilin knockout (Spino-/-) mice have decreased fat mass, increased lean mass, and improved glucose tolerance, with no difference in feeding behaviors. While spinophilin is enriched in neurons, its roles in non-neuronal tissues, such as beta cells of the pancreatic islets, are unclear. Methods & ResultsWe have corroborated and expanded upon previous studies to determine that Spino-/- mice have decreased weight gain and improved glucose tolerance in two different models of obesity. Using proteomics and immunoblotting-based approaches we identified multiple putative spinophilin interacting proteins isolated from intact pancreas and observed increased interactions of spinophilin with exocrine, ribosomal, and cytoskeletal protein classes that mediate peptide hormone production, processing, and/or release in Leprdb/db and/or high fat-fed (HFF) models of obesity. Moreover, loss of spinophilin specifically in pancreatic beta cells improved glucose tolerance without impacting body weight. ConclusionOur data further support a role for spinophilin in mediating pathophysiological changes in body weight and whole-body metabolism associated with obesity and provide the first evidence that spinophilin mediates obesity-dependent pancreatic dysfunction that leads to deficits in glucose homeostasis or diabesity.

cell biology↗

bioRxiv2022

Spinophilin limits metabotropic glutamate receptor 5 scaffolding to the postsynaptic density and cell type-specifically mediates excessive grooming

BackgroundConstitutive knockout of the obsessive-compulsive disorder-associated protein, disks large associated protein 3 (SAPAP3), results in repetitive motor dysfunction, such as excessive grooming, caused by increased metabotropic glutamate receptor 5 (mGluR5) activity in striatal direct- and indirect pathway medium spiny neurons (dMSNs and iMSNs, respectively). However, MSN subtype-specific signaling mechanisms that mediate mGluR5-dependent adaptations underlying excessive grooming are not fully understood. Here, we investigate the MSN subtype-specific roles of the striatal signaling hub protein, spinophilin, in mediating repetitive motor dysfunction associated with mGluR5 function. MethodsQuantitative 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 was measured using our novel conditional spinophilin mouse model that had spinophilin knocked out from striatal dMSNs or/and iMSNs. ResultsLoss of spinophilin only in iMSNs 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 and treatment with the mGluR5-specific positive allosteric modulator (VU0360172) without impacting locomotion-relevant behavior. Biochemically, we determined spinophilins protein interaction correlates with grooming behavior and loss of spinophilin shifts mGluR5 interactions from lipid-raft associated proteins toward postsynaptic density (PSD) proteins implicated in psychiatric disorders. ConclusionsThese 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.

neuroscience↗

bioRxiv2021

Spinophilin limits GluN2B-containing NMDAR activity and sequelae associated with excessive hippocampal NMDAR function.

N-methyl-D-Aspartate receptors (NMDARs) are calcium-permeable ion channels that are ubiquitously expressed within the glutamatergic postsynaptic density. Phosphorylation of NMDAR subunits defines receptor activity and surface localization. Modulation of NMDAR phosphorylation by kinases and phosphatases regulates calcium entering the cell and subsequent activation of calcium-dependent processes. Spinophilin is the major synaptic protein phosphatase 1 (PP1) targeting protein that controls phosphorylation of myriad substrates via targeting or inhibition of PP1. Spinophilin limits NMDAR function in a PP1-dependent manner and we have previously shown that spinophilin sequesters PP1 away from the GluN2B subunit of the NMDAR, which results in increased phosphorylation of Ser-1284. However, how spinophilin modifies NMDAR function is unclear. Herein, we detail that while Ser-1284 phosphorylation increases calcium influx via GluN2B-containing NMDARs, overexpression of spinophilin decreases GluN2B-containing NMDAR activity by decreasing its surface expression. In hippocampal neurons isolated from spinophilin knockout animals there is an increase in cleaved caspase-3 levels compared to wildtype mice; however, this effect is not exclusively due to NMDAR activation; suggesting multiple putative mechanisms by which spinophilin may modulate caspase cleavage. Behaviorally, our data suggest that spinophilin knockout mice have deficits in spatial cognitive flexibility, a behavior associated GluN2B function within the hippocampus. Taken together, our data demonstrate a unique mechanism by which spinophilin modulates GluN2B containing NMDAR phosphorylation, channel function, and trafficking and that loss of spinophilin promotes pathological sequelae associated with GluN2B dysfunction. HIGHLIGHTSO_LISpinophilin bidirectionally regulates GluN2B-containing NMDAR function. C_LIO_LILoss of spinophilin in primary hippocampal neurons increases a pro-apoptotic marker. C_LIO_LILoss of spinophilin in vivo decreases measures of spatial cognitive flexibility. C_LI Graphical AbstractSpinophilin increases the phosphorylation of Ser-1284 on GluN2B, thereby enhancing calcium influx through the GluN2B containing NMDARs. In contrast, spinophilin limits GluN2B-containing surface expression putatively due to modulation of GluN2B interactions with endocytotic proteins. Since the second effect of spinophilin occurs independent of the first, we observe an overall decrease in calcium influx through GluN2B containing NMDARs when spinophilin is present. This low, basal calcium influx is less likely to be promote calcium-dependent activation of caspase and downstream apoptotic pathways and permits flexible search strategies and behaviors. In the absence of spinophilin, the spinophilin-driven internalization of the receptors is decreased, more receptors are expressed on the surface and calcium influx into the cell is increased. This high levels of intracellular calcium triggers apoptotic pathways leading to cell death. This impact may be more dramatic in cells with high expression of GluN2B-containing NMDA receptors. This loss of spinophilin reduces cognitive flexibility in hippocampal dependent tasks. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/424812v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1548b5org.highwire.dtl.DTLVardef@158a0aaorg.highwire.dtl.DTLVardef@19c185dorg.highwire.dtl.DTLVardef@103848b_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Prenatal Methadone Exposure Disrupts Behavioral Development and Alters Motor Neuron Intrinsic Properties and Local Circuitry

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. PME produced substantial impairments in offspring physical growth, activity in an open field, and sensorimotor milestone acquisition which were associated with alterations in motor neuron functioning and connectivity. The present study adds to the limited work examining PME by providing a comprehensive, translationally relevant characterization of how PME disrupts offspring development.

neuroscience↗

bioRxiv2018

Astrocytes Regulate the Development and Maturation of Retinal Ganglion Cells Derived from Human Pluripotent Stem Cells

Retinal ganglion cells (RGCs) form the connection between the eye and the brain, with this connectivity disrupted in numerous blinding disorders. Previous studies have demonstrated the ability to derive RGCs from hPSCs; however these cells exhibited some characteristics that indicated a limited state of maturation. Among the many factors known to influence RGC development in the retina, astrocytes are known to play a significant role in their functional maturation. Thus, efforts of the current study examined the functional maturation of hPSC-derived RGCs, including the ability of astrocytes to modulate this developmental timeline. Morphological and functional properties of RGCs were found to increase over time, with astrocytes significantly accelerating the functional maturation of hPSC-derived RGCs. The results of this study are the first of its kind to extensively study the functional and morphological maturation of RGCs in vitro, including the effects of astrocytes upon the maturation of hPSC-derived RGCs.

neuroscience↗