Browsing by Author "Yin, Fuqin"

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    Alcohol exposure disrupts mu opioid receptor-mediated long-term depression at insular cortex inputs to dorsolateral striatum
    (Nature Publishing group, 2018-04-03) Muñoz, Braulio; Fritz, Brandon M.; Yin, Fuqin; Atwood, Brady K.; Psychiatry, School of Medicine
    Drugs of abuse, including alcohol, ablate the expression of specific forms of long-term synaptic depression (LTD) at glutamatergic synapses in dorsal striatum (DS), a brain region involved in goal-directed and habitual behaviors. This loss of LTD is associated with altered DS-dependent behavior. Given the role of the µ-opioid receptor (MOR) in behavioral responding for alcohol, we explored the impact of alcohol on various forms of MOR-mediated synaptic depression that we find are differentially expressed at specific DS synapses. Corticostriatal MOR-mediated LTD (mOP-LTD) in the dorsolateral striatum occurs exclusively at inputs from anterior insular cortex and is selectively disrupted by in vivo alcohol exposure. Alcohol has no effect on corticostriatal mOP-LTD in dorsomedial striatum, thalamostriatal MOR-mediated short-term depression, or mOP-LTD of cholinergic interneuron-driven glutamate release. Disrupted mOP-LTD at anterior insular cortex–dorsolateral striatum synapses may therefore be a key mechanism of alcohol-induced neuroadaptations involved in the development of alcohol use disorders., µ-opioid receptors (MOR) are known to modulate the reward effects of drugs of abuse, and MOR activation induces long-term depression (LTD) at striatal synapses. Here the authors show that alcohol exposure disrupts MOR-induced LTD only at specific cortical inputs to the striatum.
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    Genetic disruption of the PI3K regulatory subunits, p85 alpha, p55 alpha, and p50 alpha partially normalizes gain-of-function PTPN11- induced hypersensitivity to GM-CSF in hematopoietic progenitors
    (Office of the Vice Chancellor for Research, 2011-04-08) Goodwin, Charles B.; Yang, Zhenyun; Yin, Fuqin; Chan, Rebecca J.
    Juvenile Myelomonocytic Leukemia (JMML) is a lethal myeloproliferative disorder (MPD) of children, characterized by hyperproliferation of myelomonocytic cells and hypersensitivity to Granulocyte-Monocyte Colony-Stimulating Factor (GM-CSF). JMML is frequently associated with gain-of-function mutations in PTPN11, which encodes the protein tyrosine phosphatase, Shp2, and which is known to positively regulate Ras signaling. The role of MAPK signaling in gain-of-function mutant Shp2-induced leukemogenesis is well established. In addition, phosphoAkt levels are elevated in the presence of gain-of-function Shp2 mutations, suggesting a role for Phosphatidyl-Inositol-3-Kinase (PI3K) signaling (Yang, et al, 2008). Class IA PI3K is a lipid kinase heterodimer composed of one of two regulatory subunits—p85 alpha or p85 beta—and one of three catalytic subunits—p110 alpha, p110 beta, or p110 delta. PI3K mediates proliferative and anti-apoptotic signals. We have found that there is increased interaction between the p85 alpha regulatory subunit and the p110 alpha catalytic subunit in gain-offunction mutant Shp2-expressing cells compared to WT Shp2-expressing cells. The p85 alpha regulatory subunit, along with its splice variants, p55 alpha and p50 alpha, is encoded by the gene Pik3r1. To investigate the hypothesis that p85 alpha-dependent PI3K signaling contributes to gain-of-function mutant Shp2-induced GM-CSF hypersensitivity, WT and Pik3r1-/- fetal liver-derived hematopoietic progenitor cells were transduced with WT Shp2 or gain-of-function mutant Shp2 E76K. Ablation of all the Pik3r1 isoforms resulted in a significant, but incomplete, correction of GM-CSF hypersensitivity in Shp2 E76K-expressing cells. Consistently, upon genetic disruption of Pik3r1, Akt phosphorylation was reduced in both WT Shp2- and Shp2 E76K-expressing cells compared to that seen in Pik3r1+/+ cells, but was not completely absent. Additionally, Erk activation was reduced in Pik3r1-/- cells expressing Shp2 E76K compared to that in Pik3r1+/+ cells, indicating that interruption of Shp2-mediated PI3K signaling affects the MAPK pathway as well, which likely contributes to the reduction in GM-CSF-stimulated proliferation in the Pik3r1-/- cells. Finally, treatment with the PI3K inhibitor, LY294002 resulted in complete abrogation of Akt phosphorylation in Pik3r1-/- cells transduced with Shp2 E76K, indicating that residual PI3K activity in the absence of Pik3r1 likely contributes to the incomplete correction of GM-CSF hypersensitivity and suggesting that although p85 alpha plays an important role in gain-of-function mutant Shp2-induced hyperactivation of PI3K signaling, additional p85 alpha-independent mechanisms contribute as well.
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    HCN1 channels mediate mu opioid receptor long-term depression at insular cortex inputs to the dorsal striatum
    (Wiley, 2022) Munoz, Braulio; Fritz, Brandon M.; Yin, Fuqin; Atwood, Brady K.; Pharmacology and Toxicology, School of Medicine
    Mu opioid receptors (MORs) are expressed in the dorsal striatum, a brain region that mediates goal-directed (via the dorsomedial striatum) and habitual (via the dorsolateral striatum, DLS) behaviours. Our previous work indicates that glutamate transmission is depressed when MORs are activated in the dorsal striatum, inducing MOR-mediated long-term synaptic depression (MOR-LTD) or short-term depression (MOR-STD), depending on the input. In the DLS, MOR-LTD is produced by MORs on anterior insular cortex (AIC) inputs and MOR-STD occurs at thalamic inputs, suggesting input-specific MOR plasticity mechanisms. Here, we evaluated the mechanisms of induction of MOR-LTD and MOR-STD in the DLS using pharmacology and optogenetics combined with patch-clamp electrophysiology. We found that cAMP/PKA signalling and protein synthesis are necessary for MOR-LTD expression, similar to previous studies of cannabinoid-mediated LTD in DLS. MOR-STD does not utilize these same mechanisms. We also demonstrated that cannabinoid-LTD occurs at AIC inputs to DLS. However, while cannabinoid-LTD requires mTOR signalling in DLS, MOR-LTD does not. We characterized the role of presynaptic HCN1 channels in MOR-LTD induction as HCN1 channels expressed in AIC are necessary for MOR-LTD expression in the DLS. These results suggest a mechanism in which MOR activation requires HCN1 to induce MOR-LTD, suggesting a new target for pharmacological modulation of synaptic plasticity, providing new opportunities to develop novel drugs to treat alcohol and opioid use disorders. KEY POINTS: Mu opioid receptor-mediated long-term depression at anterior insular cortex inputs to dorsolateral striatum involves presynaptic cAMP/PKA signalling and protein translation, similar to known mechanisms of cannabinoid long-term depression. Dorsal striatal cannabinoid long-term depression also occurs at anterior insular cortex inputs to the dorsolateral striatum. Dorsal striatal cannabinoid long-term depression requires mTOR signalling, similar to hippocampal cannabinoid long-term depression, but dorsal striatal mu opioid long-term depression does not require mTOR signalling. Mu opioid long-term depression requires presynaptic HCN1 channels at anterior insular cortex inputs to dorsolateral striatum.
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    A High-fat, High-sugar ‘Western’ Diet Alters Dorsal Striatal Glutamate, Opioid, and Dopamine Transmission in Mice
    (Elsevier, 2018-02) Fritz, Brandon M.; Muñoz, Braulio; Yin, Fuqin; Bauchle, Casey; Atwood, Brady K.; Psychiatry, School of Medicine
    Understanding neuroadaptations involved in obesity is critical for developing new approaches to treatment. Diet-induced neuroadaptations within the dorsal striatum have the capacity to drive excessive food seeking and consumption. Five-week-old C57BL/6J mice consumed a high-fat, high-sugar ‘western diet’ (WD) or a control ‘standard diet’ (SD) for 16 weeks. Weight gain, glucose tolerance, and insulin tolerance were measured to confirm an obese-like state. Following these 16 weeks, electrophysiological recordings were made from medium spiny neurons (MSNs) in the medial (DMS) and lateral (DLS) portions of dorsal striatum to evaluate diet effects on neuronal excitability and synaptic plasticity. In addition, fast-scan cyclic voltammetry evaluated dopamine transmission in these areas. WD mice gained significantly more weight and consumed more calories than SD mice and demonstrated impaired glucose tolerance. Electrophysiology data revealed that MSNs from WD mice demonstrated increased AMPA-to-NMDA receptor current ratio and prolonged spontaneous glutamate-mediated currents, specifically in the DLS. Evoked dopamine release was also significantly greater and reuptake slower in both subregions of WD striatum. Finally, dorsal striatal MSNs from WD mice were significantly less likely to demonstrate mu-opioid receptor-mediated synaptic plasticity. Neuronal excitability and GABAergic transmission were unaffected by diet in either striatal subregion. Our results demonstrate that a high-fat, high-sugar diet alters facets of glutamate, dopamine, and opioid signaling within the dorsal striatum, with some subregion specificity. These alterations within a brain area known to play a role in food motivation/consumption and habitual behavior are highly relevant for the clinical condition of obesity and its treatment.
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    Input-selective adenosine A1 receptor-mediated synaptic depression of excitatory transmission in dorsal striatum
    (Springer Nature, 2021-03-18) Fritz, Brandon M.; Yin, Fuqin; Atwood, Brady K.; Pharmacology and Toxicology, School of Medicine
    The medial (DMS) and lateral (DLS) dorsal striatum differentially drive goal-directed and habitual/compulsive behaviors, respectively, and are implicated in a variety of neuropsychiatric disorders. These subregions receive distinct inputs from cortical and thalamic regions which uniquely determine dorsal striatal activity and function. Adenosine A1 receptors (A1Rs) are prolific within striatum and regulate excitatory glutamate transmission. Thus, A1Rs may have regionally-specific effects on neuroadaptive processes which may ultimately influence striatally-mediated behaviors. The occurrence of A1R-driven plasticity at specific excitatory inputs to dorsal striatum is currently unknown. To better understand how A1Rs may influence these behaviors, we first sought to understand how A1Rs modulate these distinct inputs. We evaluated A1R-mediated inhibition of cortico- and thalamostriatal transmission using in vitro whole-cell, patch clamp slice electrophysiology recordings in medium spiny neurons from both the DLS and DMS of C57BL/6J mice in conjunction with optogenetic approaches. In addition, conditional A1R KO mice lacking A1Rs at specific striatal inputs to DMS and DLS were generated to directly determine the role of these presynaptic A1Rs on the measured electrophysiological responses. Activation of presynaptic A1Rs produced significant and prolonged synaptic depression (A1R-SD) of excitatory transmission in the both the DLS and DMS of male and female animals. Our findings indicate that A1R-SD at corticostriatal and thalamostriatal inputs to DLS can be additive and that A1R-SD in DMS occurs primarily at thalamostriatal inputs. These findings advance the field’s understanding of the functional roles of A1Rs in striatum and implicate their potential contribution to neuropsychiatric diseases.
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    Mu opioid receptors on vGluT2‐expressing glutamatergic neurons modulate opioid reward
    (Wiley, 2021-05) Reeves, Kaitlin C.; Kube, Megan J.; Grecco, Gregory G.; Fritz, Brandon M.; Muñoz, Braulio; Yin, Fuqin; Gao, Yong; Haggerty, David L.; Hoffman, Hunter J.; Atwood, Brady K.; Pharmacology and Toxicology, School of Medicine
    The role of Mu opioid receptor (MOR)-mediated regulation of GABA transmission in opioid reward is well established. Much less is known about MOR-mediated regulation of glutamate transmission in the brain and how this relates to drug reward. We previously found that MORs inhibit glutamate transmission at synapses that express the Type 2 vesicular glutamate transporter (vGluT2). We created a transgenic mouse that lacks MORs in vGluT2-expressing neurons (MORflox-vGluT2cre) to demonstrate that MORs on the vGluT2 neurons themselves mediate this synaptic inhibition. We then explored the role of MORs in vGluT2-expressing neurons in opioid-related behaviors. In tests of conditioned place preference, MORflox-vGluT2cre mice did not acquire place preference for a low dose of the opioid, oxycodone, but displayed conditioned place aversion at a higher dose, whereas control mice displayed preference for both doses. In an oral consumption assessment, these mice consumed less oxycodone and had reduced preference for oxycodone compared with controls. MORflox-vGluT2cre mice also failed to show oxycodone-induced locomotor stimulation. These mice displayed baseline withdrawal-like responses following the development of oxycodone dependence that were not seen in littermate controls. In addition, withdrawal-like responses in these mice did not increase following treatment with the opioid antagonist, naloxone. However, other MOR-mediated behaviors were unaffected, including oxycodone-induced analgesia. These data reveal that MOR-mediated regulation of glutamate transmission is a critical component of opioid reward.
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    A Multi-Omic Analysis of the Dorsal Striatum in an Animal Model of Divergent Genetic Risk for Alcohol Use Disorder
    (Wiley, 2021) Grecco, Gregory G.; Haggerty, David L.; Doud, Emma H.; Fritz, Brandon M.; Yin, Fuqin; Hoffman, Hunter; Mosley, Amber L.; Simpson, Edward; Liu, Yunlong; Baucum, Anthony J., II.; Atwood, Brady K.; Pharmacology and Toxicology, School of Medicine
    The development of selectively bred high and low alcohol-preferring mice (HAP and LAP, respectively) has allowed for an assessment of the polygenetic risk for pathological alcohol consumption and phenotypes associated with alcohol use disorder (AUD). Accumulating evidence indicates that the dorsal striatum (DS) is a central node in the neurocircuitry underlying addictive processes. Therefore, knowledge of differential gene, protein, and phosphorylated protein expression in the DS of HAP and LAP mice may foster new insights into how aberrant DS functioning may contribute to AUD-related phenotypes. To begin to elucidate these basal differences, a complementary and integrated analysis of DS tissue from alcohol-naïve male and female HAP and LAP mice was performed using RNA sequencing, quantitative proteomics, and phosphoproteomics. These datasets were subjected to a thorough analysis of gene ontology, pathway enrichment, and hub gene assessment. Analyses identified 2,108, 390, and 521 significant differentially expressed genes, proteins, and phosphopeptides, respectively between the two lines. Network analyses revealed an enrichment in the differential expression of genes, proteins, and phosphorylated proteins connected to cellular organization, cytoskeletal protein binding, and pathways involved in synaptic transmission and functioning. These findings suggest that the selective breeding to generate HAP and LAP mice may lead to a rearrangement of synaptic architecture which could alter DS neurotransmission and plasticity differentially between mouse lines. These rich datasets will serve as an excellent resource to inform future studies on how inherited differences in gene, protein, and phosphorylated protein expression contribute to AUD-related phenotypes.