Biology subjects

Wetsel, W. C.

Publications and source records attributed to Wetsel, W. C..

At least 19 recordsLinked to original sources

bioRxiv2025

Structure based discovery of antipsychotic-like TAAR1 agonists

Schizophrenia is a severe mental illness whose current treatments primarily target dopamine and serotonin receptors. These drugs often cause side effects and vary in effectiveness across patients. The trace amine-associated receptor 1 (TAAR1), which modulates monoamine signaling, has emerged as a promising alternative target. To discover new TAAR1 ligands, we computationally docked 65 million molecules against the active state of TAAR1 and experimentally tested 55 of those highly ranked. Fourteen molecules active against TAAR1 with potencies ranging from mid-nanomolar to micromolar, all as agonists. This high functional selectivity may reflect the compact conformation adopted by the activated TAAR1 orthosteric site. While this was favorable for agonist prioritization, simulations suggest that it can be over-optimized for initial hit rates at the expense of subsequent affinity maturation. Here, hit optimization yielded nanomolar agonists whose docking-predicted poses were confirmed by cryo-EM. Three agonists had high brain exposure and potencies apparently better than the investigational drug ulotaront and sufficient for behavioral studies. All three potently normalized amphetamine-induced pre-pulse inhibition in mice, a model for schizophrenia, without catalepsy, a common side effect of traditional antipsychotics.

biochemistry↗

bioRxiv2025

Hidden Bias: GPCR Polymorphisms and the Genomic Landscape of β- Arrestin Signaling

Clinically, no human diseases are currently diagnosed as being directly driven by {beta}- arrestins. Nonetheless, there is growing interest in developing {beta}-arrestin-biased drugs, due to the key regulatory role of {beta}-arrestins in modulating the cellular signaling of most G protein-coupled receptors (GPCRs). In cell-based studies of rhodopsin-family GPCRs, mutations in a conserved proline-hydrophobic (ProH) motif within the second intracellular loop (ICL2) have been shown to alter {beta}-arrestin signaling bias. The clinical relevance of such mutations in humans is unknown. However, if naturally occurring single nucleotide polymorphisms (SNPs) affecting this ProH motif exist across the GPCR family, then cross-referencing these genetic variants with large-scale population sequencing and epidemiologic data could reveal potential roles for {beta}-arrestin signaling in human health. In this report, we identify SNPs in human GPCRs that correspond to ProH substitutions, and we show that, in the neurotensin receptor NTSR1, these variants can indeed shift signaling bias. We also estimate a lower-bound population frequency for such SNPs, suggesting that although rare for any given receptor, their cumulative prevalence across the GPCR superfamily may be large enough to impact phenotypic variation. Together with emerging data from biased ligands, our findings support the idea that genetic variations in {beta}-arrestin signaling could represent a meaningful source of therapeutic relevance. Significance statementMutations altering G protein-coupled receptor (GPCR) signaling can affect health. We have identified a specific amino acid determinant in intracellular loop (ICL2) of human rhodopsin family GPCRs that influences {beta}-arrestin signaling. Although the medical consequences of this determinant remain unclear, we show that single nucleotide polymorphisms (SNPs) affecting the determinant routinely occur. By studying neurotensin receptor NTSR1, we confirm that the SNP alters {beta}-arrestin signaling bias. While individually rare per receptor, these SNPs may collectively contribute to {beta}-arrestin-related phenotypic changes in the human population. Our findings, combined with research on biased drugs, support the idea that {beta}-arrestin signaling might serve as a useful therapeutic target, opening new possibilities for precision medicine.

biochemistry↗

bioRxiv2024

A two-dose regimen of Qβ virus-like particle-based vaccines elicit protective antibodies against heroin and fentanyl

Opioid overdoses and the growing rate of opioid use disorder (OUD) are major public health concerns, particularly in the United States. Current treatment approaches for OUD have failed to slow the growth of the opioid crisis. Opioid vaccines have shown pre-clinical success in targeting multiple different opioid drugs. However, the need for many immunizations can limit their clinical implementation. In this study, we investigate the development of novel opioid vaccines by independently targeting fentanyl and the active metabolites of heroin using a bacteriophage virus-like particle (VLP) vaccine platform. We establish the successful conjugation of haptens to bacteriophage Q{beta} VLPs and demonstrate immunogenicity of Q{beta}-fentanyl, Q{beta}-morphine, and Q{beta}-6-acetylmorphine in animal models after one or two immunizations. We show that in independently or in combination, these vaccines elicit high-titer, high-avidity, and durable antibody responses. Moreover, we reveal their protective capacities against heroin or fentanyl challenge after two immunizations. Overall, these findings establish Q{beta}-VLP conjugated vaccines for heroin and fentanyl as very promising opioid vaccine candidates.

immunology↗

bioRxiv2024

Combination of Haloperidol with UNC9994, β-arrestin-biased analog of Aripiprazole, ameliorates schizophrenia-related phenotypes induced by NMDAR deficit in mice.

BackgroundGlutamatergic system dysfunction, particularly involving the N-methyl-D-aspartate receptor (NMDAR), contributes to a full spectrum of schizophrenia-like symptoms, including the cognitive and negative symptoms that are resistant to treatment with antipsychotic drugs (APDs). Aripiprazole, an atypical antipsychotic drug (APD), acts as a dopamine partial agonist and its combination with haloperidol (a typical APD) has been suggested as a potential strategy to improve schizophrenia symptoms. Recently, an analog of aripiprazole - UNC9994 was developed. UNC9994 does not affect D2R-mediated Gi/o protein signaling but acts as a partial agonist for D2R/{beta}-arrestin interactions. Hence, our objective was to probe the effects of co-administrating haloperidol with UNC9994 in NMDAR mouse models of schizophrenia. MethodsNMDAR hypofunction was induced pharmacologically by acute injection of MK-801 (NMDAR pore blocker; 0.15 mg/kg) and genetically by knockdown of Grin1 gene expression in mice, which have a 90% reduction in NMDAR levels (Grin1-KD). After intraperitoneal injections of vehicle, haloperidol (0.15 mg/kg), UNC9994 (0.25 mg/kg) or their combination mice were tested in open field, Pre-Pulse inhibition (PPI), Y-maze and Puzzle box. ResultsOur findings indicate that low dose co-administration of UNC9994 and haloperidol reduces hyperactivity in MK-801-treated animals and in Grin1-KD mice. Furthermore, this dual administration effectively reverses PPI deficits, repetitive/rigid behavior in the Y-maze, and deficient executive function in the Puzzle box in both animal models. ConclusionsThe dual administration of haloperidol with UNC9994 at low doses represents a promising approach to ameliorate positive, negative, and cognitive symptoms of schizophrenia. Significance statementSchizophrenia is a devastating mental disorder and characterized by positive, negative, and cognitive symptoms. Cognitive and negative symptoms remain a focus of research dedicated to development of effective antipsychotic drugs (APDs). Aripiprazole, an atypical APD, acts as a dopamine partial agonist and its combination with haloperidol (a typical APD) has been suggested as a potential strategy to improve schizophrenia symptoms. An analog of aripiprazole - UNC9994 was recently developed, which does not affect D2R-mediated Gi/o protein signaling but acts as a partial agonist for D2R/{beta}-arrestin interactions. Our pre-clinical findings on pharmacological (MK-801, 0.15 mg/kg) and genetic (Grin1-KD) mouse models of NMDAR deficiency showed that the dual administration of UNC9994 (0.25 mg/kg) with haloperidol (0.15 mg/kg) at low doses reduces hyperactivity, corrects prepulse inhibition (PPI) deficits, rigid behavior in the Y-maze, and deficient executive function in the Puzzle box. Further studies of the polypharmacy of UNC9994 with APDs is essential to facilitate translational studies in clinics.

pharmacology and toxicology↗

bioRxiv2024

Presynaptic Rac1 in the hippocampus selectively regulates working memory

One of the most extensively studied members of the Ras superfamily of small GTPases, Rac1 is an intracellular signal transducer that remodels actin and phosphorylation signaling networks. Previous studies have shown that Rac1-mediated signaling is associated with hippocampal-dependent working memory and longer-term forms of learning and memory and that Rac1 can modulate forms of both pre- and postsynaptic plasticity. How these different cognitive functions and forms of plasticity mediated by Rac1 are linked, however, is unclear. Here, we show that spatial working memory is selectively impaired following the expression of a genetically encoded Rac1-inhibitor at presynaptic terminals, while longer-term cognitive processes are affected by Rac1 inhibition at postsynaptic sites. To investigate the regulatory mechanisms of this presynaptic process, we leveraged new advances in mass spectrometry to identify the proteomic and post-translational landscape of presynaptic Rac1 signaling. We identified serine/threonine kinases and phosphorylated cytoskeletal signaling and synaptic vesicle proteins enriched with active Rac1. The phosphorylated sites in these proteins are at positions likely to have regulatory effects on synaptic vesicles. Consistent with this, we also report changes in the distribution and morphology of synaptic vesicles and in postsynaptic ultrastructure following presynaptic Rac1 inhibition. Overall, this study reveals a previously unrecognized presynaptic role of Rac1 signaling in cognitive processes and provides insights into its potential regulatory mechanisms.

animal behavior and cognition↗

bioRxiv2023

A suite of engineered mice for interrogating psychedelic drug actions

Psychedelic drugs like lysergic acid diethylamide (LSD) and psilocybin have emerged as potentially transformative therapeutics for many neuropsychiatric diseases, including depression, anxiety, post-traumatic stress disorder, migraine, and cluster headaches. LSD and psilocybin exert their psychedelic effects via activation of the 5-hydroxytryptamine 2A receptor (HTR2A). Here we provide a suite of engineered mice useful for clarifying the role of HTR2A and HTR2A-expressing neurons in psychedelic drug actions. We first generated Htr2a-EGFP-CT-IRES-CreERT2 mice (CT:C-terminus) to independently identify both HTR2A-EGFP-CT receptors and HTR2A-containing cells thereby providing a detailed anatomical map of HTR2A and identifying cell types that express HTR2A. We also generated a humanized Htr2a mouse line and an additional constitutive Htr2A-Cre mouse line. Psychedelics induced a variety of known behavioral changes in our mice validating their utility for behavioral studies. Finally, electrophysiology studies revealed that extracellular 5-HT elicited a HTR2A-mediated robust increase in firing of genetically-identified pyramidal neurons--consistent with a plasma membrane localization and mode of action. These mouse lines represent invaluable tools for elucidating the molecular, cellular, pharmacological, physiological, behavioral, and other actions of psychedelic drugs in vivo.

neuroscience↗

bioRxiv2023

The G protein biased serotonin 5-HT 2A receptor agonist lisuride exerts anti-depressant drug-like activities in mice

There is now evidence from multiple Phase II clinical trials that psychedelic drugs can exert long-lasting anxiolytic, anti-depressant, and anti-drug abuse (nicotine and ethanol) effects in patients. Despite these benefits, the hallucinogenic actions of these drugs at the serotonin 2A receptor (5-HT2AR) limit their clinical use in diverse settings. Activation of the 5-HT2AR can stimulate both G protein and {beta}-arrestin ({beta}Arr) -mediated signaling. Lisuride is a G protein biased agonist at the 5-HT2AR and, unlike the structurally-related LSD, the drug does not typically produce hallucinations in normal subjects at routine doses. Here, we examined behavioral responses to lisuride, in wild-type (WT), {beta}Arr1-KO, and {beta}Arr2-KO mice. In the open field, lisuride reduced locomotor and rearing activities, but produced a U-shaped function for stereotypies in both {beta}Arr lines of mice. Locomotion was decreased overall in {beta}Arr1-KOs and {beta}Arr2-KOs, relative to WT controls. Incidences of head twitches and retrograde walking to lisuride were low in all genotypes. Grooming was depressed in {beta}Arr1 mice, but was increased then decreased in {beta}Arr2 animals with lisuride. Prepulse inhibition (PPI) was unaffected in {beta}Arr2 mice, whereas 0.5 mg/kg lisuride disrupted PPI in {beta}Arr1 animals. The 5-HT2AR antagonist MDL100907 failed to restore PPI in {beta}Arr1 mice, whereas the dopamine D2/D3 antagonist raclopride normalized PPI in WTs but not in {beta}Arr1-KOs. Using vesicular monoamine transporter 2 mice, lisuride reduced immobility times in tail suspension and promoted a preference for sucrose that lasted up to 2 days. Together, it appears {beta}Arr1 and {beta}Arr2 play minor roles in lisurides actions on many behaviors, while this drug exerts anti-depressant drug-like responses without hallucinogenic-like activities.

pharmacology and toxicology↗

bioRxiv2022

Identification and Characterization of ML321: a Novel and Highly Selective D2 Dopamine Receptor Antagonist with Efficacy in Animal Models that Predict Atypical Antipsychotic Activity

We have developed and characterized a novel D2R antagonist with exceptional GPCR selectivity - ML321. In functional profiling screens of 168 different GPCRs, ML321 showed little activity beyond potent inhibition of the D2R, and to a lesser extent the D3R, demonstrating excellent receptor selectivity. The D2R selectivity of ML321 may be related to the fact that, unlike other monoaminergic ligands, ML321 lacks a positively charged amine group and adopts a unique binding pose within the orthosteric binding site of the D2R. PET imaging studies in non-human primates demonstrated that ML321 penetrates the CNS and occupies the D2R in a dose-dependent manner. Behavioral paradigms in rats demonstrate that ML321 can selectively antagonize a D2R-mediated response (hypothermia) while not affecting a D3R-mediated response (yawning) using the same dose of drug, thus indicating exceptional in vivo selectivity. We also investigated the effects of ML321 in animal models that are predictive of antipsychotic efficacy in humans. We found that ML321 attenuates both amphetamine- and phencyclidine-induced locomotor activity and restored pre-pulse inhibition (PPI) of acoustic startle in a dose-dependent manner. Surprisingly, using doses that were maximally effective in both the locomotor and PPI studies, ML321 was relatively ineffective in promoting catalepsy. Kinetic studies revealed that ML321 exhibits slow-on and fast-off receptor binding rates, similar to those observed with atypical antipsychotics with reduced extrapyramidal side effects. Taken together, these observations suggest that ML321, or a derivative thereof, may exhibit "atypical" antipsychotic activity in humans with significantly fewer side effects than observed with currently FDA-approved D2R antagonists.

pharmacology and toxicology↗

bioRxiv2022

Chemico-genetic Analysis of Native Autism Proteomes Reveals Shared Biology Predictive of Functional Modifiers

One of the main drivers of autism spectrum disorder is risk alleles within hundreds of genes, which may interact within shared but unknown protein complexes. Here we develop a scalable genome-editing-mediated approach to target 14 high-confidence autism risk genes within the mouse brain for proximity-based endogenous proteomics, achieving high specificity spatial interactomes compared to prior methods. The resulting native proximity interactomes are enriched for human genes dysregulated in the brain of autistic individuals and reveal unexpected and highly significant interactions with other lower-confidence autism risk gene products, positing new avenues to prioritize genetic risk. Importantly, the datasets are enriched for shared cellular functions and genetic interactions that may underlie the condition. We test this notion by spatial proteomics and CRISPR-based regulation of expression in two autism models, demonstrating functional interactions that modulate mechanisms of their dysregulation. Together, these results reveal native proteome networks in vivo relevant to autism, providing new inroads for understanding and manipulating the cellular drivers underpinning its etiology.

neuroscience↗

bioRxiv2022

Conserved YKL-40 changes in mice and humans after postoperative delirium.

Delirium is a common postoperative neurologic complication among older adults. Despite its prevalence of 14-50% and likely association with inflammation, the exact mechanisms underlying postoperative delirium are unclear. This project aimed at characterizing systemic and central nervous system (CNS) inflammatory changes following surgery in both mice and humans. Matched plasma and cerebrospinal fluid (CSF) samples from the "Investigating Neuroinflammation Underlying Postoperative Brain Connectivity Changes, Postoperative Cognitive Dysfunction, Delirium in Older Adults" (INTUIT; NCT03273335) were used to parallel murine endpoints. Delirium-like behavior was evaluated in aged mice using the 5-Choice Serial Reaction Time Test (5-CSRTT). Using a well-established orthopedic surgical model in the FosTRAP reporter mouse, we detected neuronal changes in the prefrontal cortex, an area implicated in attention, but notably not in the hippocampus. In aged mice, plasma interleukin-6 (IL-6), chitinase-3-like protein 1 (YKL-40), and neurofilament light chain (NfL) levels increased after orthopedic surgery, but hippocampal YKL-40 expression was decreased. Given the growing role of YKL-40 in delirium and other neurodegenerative conditions, we assayed human plasma and CSF samples. Plasma YKL-40 levels were also similarly increased after surgery, with a trend toward greater post-operative plasma YKL-40 increase in patients with delirium. In contrast to plasma, YKL-40 levels in CSF decreased following surgery, which paralleled the findings in the mouse brain. Finally, we confirmed changes in blood-brain barrier (BBB) after surgery as early as 9 hours in mice, which warrants for more detailed and acute evaluations of BBB integrity following surgery in humans. All together, these results provide a nuanced understanding of the neuroimmune interactions underlying post-operative delirium in mice and humans, and highlight translational biomarkers to test potential cellular targets and mechanisms.

neuroscience↗

bioRxiv2022

Nervous system reduction in branched-chain amino acid metabolism disrupts hippocampal neurogenesis and memory

A role for macronutrient metabolism in learning and memory is supported by numerous epidemiological studies. The Ppm1k gene encodes the branched-chain keto acid dehydrogenase (BCKDH) phosphatase that promotes the metabolism of branched-chain amino acids (BCAA). Here we show that nervous system deletion of Ppm1k in mice increases BCAA levels in brain tissue but not in plasma. These mice have significant impairments in working memory accompanied by a robust accumulation of DCX+/NeuroD1+ immature neurons within the dentate gyrus granule cell layer. Through single cell RNA sequencing and pathway analysis we identified substantial increases in transit-amplifying cells and immature neurons along with activated hedgehog signaling in Ppm1k deficient primary neural stem cells (NSCs). Inhibition of mTOR signaling reversed the effects of Ppm1k deletion on neuronal progenitor gene activation in primary NSCs. Together our findings uncover a new molecular link between BCAA metabolism, hippocampal neurogenesis, and cognitive performance.

neuroscience↗

bioRxiv2022

Structure-based Discovery of Conformationally Selective Inhibitors of the Serotonin Transporter

The serotonin transporter (SERT) removes synaptic serotonin and is the target of anti-depressant drugs. SERT adopts three conformations: outward-open, occluded, and inward-open. All known inhibitors target the outward-open state except ibogaine, which has an unusual anti-depressant profile and stabilizes the inward-open conformation. Unfortunately, ibogaine is promiscuous and cardiotoxic, limiting understanding of inward-open state ligands. We computationally docked over 200 million small molecules against the ibogaine stabilized inward-open state of SERT. Thirty-six top-ranking compounds were synthesized and thirteen inhibited with potencies ranging from 29 to 5000 nM. Structure-based optimization led to two novel inhibitors with Ki values down to 3 nM. The new molecules stabilized an outward-closed state of the transporter and had little activity against off-targets. A cryo-EM structure of one of these bound to SERT confirmed the predicted geometry. In mouse behavioral assays, both had anxiolytic and anti-depressant activity, with potencies up to 200 better than fluoxetine.

biochemistry↗

bioRxiv2021

Effects of LSD are differentially modulated in arrestin knockout mice

Recent evidence suggests that psychedelic drugs can exert beneficial effects on anxiety, depression, and ethanol and nicotine abuse in humans. However, the hallucinogenic side-effects of psychedelics often preclude their clinical use. Lysergic acid diethylamide (LSD) is a prototypical hallucinogen and its psychedelic actions are exerted through the 5-HT2A serotonin receptor (5-HT2AR). 5-HT2AR activation stimulates Gq- and {beta}-arrestin-({beta}Arr) mediated signaling. To separate effects of these signaling modes, we have used {beta}Arr1 and {beta}Arr2 mice. We find that LSD stimulates motor activities to similar extents in WT and {beta}Arr1-KO mice, with non-significant effects in {beta}Arr2-KOs. LSD robustly stimulates many surrogates of psychedelic drug actions including head twitches, grooming, retrograde walking, and nose poking in WT and {beta}Arr1-KO animals. In contrast, LSD only slightly stimulates head twitches in {beta}Arr2-KO mice, without effects on retrograde walking or nose poking. The 5-HT2AR antagonist MDL100907 (MDL) blocks these LSD effects. LSD also disrupts prepulse inhibition (PPI) in WT and {beta}Arr1-KOs; PPI is unaffected in {beta}Arr2-KOs. MDL restores PPI in WT mice, but this antagonist is without effect and haloperidol is required in {beta}Arr1-KOs. LSD produces a biphasic body-temperature response in WT mice, a monophasic response in {beta}Arr1-KOs, and is without effect in {beta}Arr2 mutants. Both MDL and the 5-HT1AR antagonist, WAY 100635 (WAY), block the effects of LSD on body temperatures in WT mice, whereas WAY is effective in {beta}Arr1-KOs. Collectively, these results reveal that LSD produces diverse behavioral effects through {beta}Arr1 and {beta}Arr2, and that LSDs psychedelic drug-like actions appear to require {beta}Arr2.

neuroscience↗

bioRxiv2020

Establishment of Multi-stage Models of Drug Taking and Seeking in Mice

A genetically tractable animal model would provide a needed strategy to resolve the biological basis of drug addiction. Intravenous self-administration (IVSA) is the gold standard for modeling cocaine and opioid addiction in animals, but technical limitations have precluded the widespread use of IVSA in mice. Here, we describe the first IVSA paradigms for mice that capture the multi-stage nature of the disease and permit predictive modeling. Mice with long-standing indwelling jugular catheters engaged in cocaine or opioid-associated lever responding that was fixed ratio- and dose-dependent, extinguished by the withholding of drug, and reinstated by the presentation of paired cues. Machine learning revealed that vulnerability to drug seeking and relapse were predicted by a mouses a priori response to novelty, sensitivity to drug-induced locomotion, and drug-taking behavior. Application of this behavioral and analysis approach to genetically-engineered mice will facilitate the identification of the neural circuits driving addiction susceptibility and relapse and focused therapeutic development.

neuroscience↗

bioRxiv2020

Annexin-A1 tripeptide attenuates surgery-induced neuroinflammation and memory deficits through regulation of the NLRP3 inflammasome

Neuroinflammation is a growing hallmark of perioperative neurocognitive disorders (PNDs), including delirium and longer-lasting cognitive deficits. We have developed a clinically-relevant orthopedic mouse model to study the impact of a common surgical procedure on the vulnerable brain. The mechanism underlying PNDs remain unknown. Here we evaluated the impact of surgical trauma on the NLRP3 inflammasome signaling, including the expression of apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, and IL-1{beta} in the hippocampus of C57BL6/J male mice, adult (3-months) and aged (>18-months). Surgery triggered ASC specks formation in CA1 hippocampal microglia, but without inducing significant morphological changes in NLRP3 and ASC knockout mice. Since no therapies are currently available to treat PNDs, we assessed the neuroprotective effects of a biomimetic peptide derived from the endogenous inflammation-ending molecule, Annexin-A1 (ANXA1). We tested the hypothesis that this peptide (ANXA1sp) inhibits NLRP3 inflammasome activation, thus preventing microglial activation and hippocampal-dependent memory deficits. Together these results uncover a previously underrecognized role of the NLRP3 inflammasome in triggering postoperative neuroinflammation and offer a new target for advancing treatment of PNDs through resolution of inflammation.

neuroscience↗

bioRxiv2019

The broad spectrum mixed-lineage kinase 3 inhibitor URMC-099 prevents acute microgliosis and cognitive decline in a mouse model of perioperative neurocognitive disorders

Perioperative neurocognitive disorders (PND), including delirium and postoperative cognitive dysfunction, are serious complications that afflict up to 50% of surgical patients and for which there are no disease-modifying therapeutic options. Here, we test whether prophylactic treatment with the broad spectrum mixed-lineage kinase 3 inhibitor URMC-099 prevents surgery-induced neuroinflammation and cognitive impairment in a translational model of orthopedic surgery-induced PND. We used a combination of two-photon scanning laser microscopy and CLARITY with light-sheet microscopy to define surgery-induced changes in microglial dynamics and morphology. Orthopedic surgery induced widespread microglial activation in the hippocampus and cortex that accompanied impairments in episodic memory. URMC-099 prophylaxis prevented these neuropathological sequelae without impacting bone fracture healing. Together, these findings provide compelling evidence for the advancement of URMC-099 as a therapeutic option for PND.

neuroscience↗

bioRxiv2019

GIT2 is dispensable for normal learning and memory function due to a predominant brain GIT2 splice variant that evades GIT/PIX complexes.

G protein-coupled receptor kinase-interacting protein 2 (GIT2) and GIT1 are highly similar, sharing the same domain structure and many binding partners. The most important GIT partners are the p21-activated protein kinase-interacting exchange factor (PIX) proteins, since through homomeric and heteromeric interactions, GIT and PIX proteins form oligomeric GIT/PIX complexes. Oligomeric GIT/PIX complexes function both as regulators of small GTP-binding proteins and as scaffolds for signalling molecules, including p21-activated protein kinases (PAKs). Deficits in learning and memory have been demonstrated in GIT1 knockout mice, and it has been assumed that GIT2 also would affect learning and memory. Unexpectedly, we find that GIT2-deficient mice respond normally in multiple tests of learning and memory, and have normal hippocampal long-term potentiation. Further, we find no evidence that GIT2 regulates ADHD-like phenotypes. To investigate why GIT2 and GIT1 differ so markedly in the brain, we identified the major isoform of GIT2 in the brain as a previously uncharacterized splice variant, GIT2({Delta}BCE). This variant cannot dimerize or form oligomeric complexes with PIX proteins, and is thus incapable of regulating PAK in synapses, compared to oligomeric GIT1/PIX complexes. Because localized activation of PAK in synapses is required for structural plasticity underlying cognitive performance, loss of monomeric GIT2({Delta}BCE) in the brain does not influence these responses.

animal behavior and cognition↗

bioRxiv2018

The cortico-striatal circuit regulates sensorimotor gating via Disc1/Huntingtin-mediated Bdnf transport

Sensorimotor information processing that underlies normal cognitive and behavioral traits is dysregulated across a subset of neurological and psychiatric disorders. The cross-disease deficit in sensorimotor gating poses a unique opportunity to integrate hierarchical findings at molecular, cellular, through circuitry levels to obtain an in-depth mechanistic understanding of this process that contributes to brain physiology and pathophysiology beyond categorical segmentation of brain disorders. Based on circuitry recording with wild-type mice, we demonstrated that the cortico-striatal projection mediates sensorimotor gating responses during prepulse inhibition (PPI) task. We also found that these circuitry responses were disrupted in Disc1 locus-impairment (LI) mice, a model representing neuropsychiatric conditions. Thus, we hypothesized that Disc1-mediated molecular and cellular machinery along the cortico-striatal circuit may regulate sensorimotor gating. Anatomical and biochemical analyses of Disc1-LI mice revealed attenuated Bdnf transport along the cortico-striatal circuit. Pharmacologically augmenting Bdnf transport by chronic lithium administration, in part via Ser-421 phosphorylation of Huntingtin (Htt) and its integration into the motor machinery, restored the striatal Bdnf levels and PPI deficits in Disc1-LI mice, suggesting that the Bdnf transport attenuation mechanistically underlies the circuitry and behavioral deficits. These results also shed light on a novel mechanism and utility of lithium that is currently used as a major mood stabilizer in clinical settings. Collectively, the present study illustrates integrative biological mechanisms for sensorimotor gating, underscoring the cross-disease nature of this behavioral dimension and translational utility of the findings under the era of precision medicine in brain disorders.

neuroscience↗