Glycine transporter-1 inhibition by NFPS promotes neuroprotection against striatal damage models.

The striatum, an essential component of the brain's motor and reward systems, plays a pivotal role in a wide array of cognitive processes. Its dysfunction is a hallmark of neurodegenerative diseases like Parkinson's disease (PD) and Huntington's disease (HD), leading to profound motor and cognitive deficits. These conditions are often related to excitotoxicity, primarily due to overactivation of NMDA receptors (NMDAR). In the synaptic cleft, glycine transporter type 1 (GlyT1) controls the glycine levels, a NMDAR co-agonist, which modulates NMDAR function. This research explored the neuroprotective potential of NFPS, a GlyT1 inhibitor, in murine models of striatal injury. Employing models of neurotoxicity induced by 6-hydroxydopamine (PD model) and quinolinic acid (HD model), we assessed the effectiveness of NFPS pre-treatment in maintaining the integrity of striatal neurons and averting neuronal degeneration. The results indicated that NFPS pre-treatment conferred significant neuroprotection, reducing neuronal degeneration, protecting dopaminergic neurons, and preserving dendritic spines within the striatum. Additionally, this pre-treatment notably mitigated motor impairments resulting from striatal damage. The study revealed that GlyT1 inhibition led to substantial changes in the ratios of NMDAR subunits GluN2A/GluN1 and GluN2B/GluN1, 24 h after NFPS treatment. These findings underscore the neuroprotective efficacy of GlyT1 inhibition, proposing it as a viable therapeutic strategy for striatum-related damage.

Transport mechanism and pharmacology of the human GlyT1.

The glycine transporter 1 (GlyT1) plays a crucial role in the regulation of both inhibitory and excitatory neurotransmission by removing glycine from the synaptic cleft. Given its close association with glutamate/glycine co-activated NMDA receptors (NMDARs), GlyT1 has emerged as a central target for the treatment of schizophrenia, which is often linked to hypofunctional NMDARs. Here, we report the cryo-EM structures of GlyT1 bound with substrate glycine and drugs ALX-5407, SSR504734, and PF-03463275. These structures, captured at three fundamental states of the transport cycle-outward-facing, occluded, and inward-facing-enable us to illustrate a comprehensive blueprint of the conformational change associated with glycine reuptake. Additionally, we identified three specific pockets accommodating drugs, providing clear insights into the structural basis of their inhibitory mechanism and selectivity. Collectively, these structures offer significant insights into the transport mechanism and recognition of substrate and anti-schizophrenia drugs, thus providing a platform to design small molecules to treat schizophrenia.

Dual Role of Dysfunctional Asc-1 Transporter in Distinct Human Pathologies, Human Startle Disease, and Developmental Delay.

Human startle disease is associated with mutations in distinct genes encoding glycine receptors, transporters or interacting proteins at glycinergic synapses in spinal cord and brainstem. However, a significant number of diagnosed patients does not carry a mutation in the common genes GLRA1, GLRB, and SLC6A5 Recently, studies on solute carrier 7 subfamily 10 (SLC7A10; Asc-1, alanine-serine-cysteine transporter) knock-out (KO) mice displaying a startle disease-like phenotype hypothesized that this transporter might represent a novel candidate for human startle disease. Here, we screened 51 patients from our patient cohort negative for the common genes and found three exonic (one missense, two synonymous), seven intronic, and single nucleotide changes in the 5' and 3' untranslated regions (UTRs) in Asc-1. The identified missense mutation Asc-1G307R from a patient with startle disease and developmental delay was investigated in functional studies. At the molecular level, the mutation Asc-1G307R did not interfere with cell-surface expression, but disrupted glycine uptake. Substitution of glycine at position 307 to other amino acids, e.g., to alanine or tryptophan did not affect trafficking or glycine transport. By contrast, G307K disrupted glycine transport similar to the G307R mutation found in the patient. Structurally, the disrupted function in variants carrying positively charged residues can be explained by local structural rearrangements because of the large positively charged side chain. Thus, our data suggest that SLC7A10 may represent a rare but novel gene associated with human startle disease and developmental delay.

The cell volume-regulatory glycine transporter GLYT1 is activated following metallopeptidase-mediated detachment of the oocyte from the zona pellucida.

Independent cell volume regulation is first acquired by the oocyte in two steps that occur during meiotic maturation: (1) activation of the glycine transporter GLYT1 (Slc6a9) that mediates the intracellular accumulation of glycine to provide osmotic support in the mature egg and early preimplantation embryo, and (2) release of the oocyte from the strong attachment to its rigid extracellular matrix shell, the zona pellucida (ZP). It was recently shown that oocyte-ZP detachment requires metallopeptidase activity that is proposed to cleave transmembrane ZP proteins connecting the oocyte to the ZP. It is unknown, however, how GLYT1 is activated. We hypothesized that oocyte-ZP detachment precedes and may be required for GLYT1 activation. In identically treated pools of oocytes, oocyte-ZP detachment occurred ~20 min before GLYT1 activation. In individual oocytes, GLYT1 activity was detected only in those that were mostly or fully detached. Blocking detachment using previously validated small molecule metallopeptidase inhibitors partly suppressed GLYT1 activation. However, removal of the ZP did not accelerate GLYT1 activation. This indicates that oocyte-ZP detachment or cleavage of transmembrane ZP proteins may be required for GLYT1 to become fully activated, or alternatively that metallopeptidase activity independently affects both detachment and GLYT1 activation.

Novel Phenylene Lipids That Are Positive Allosteric Modulators of Glycine Receptors and Inhibitors of Glycine Transporter 2.

Chronic pain is a complex condition that remains resistant to current therapeutics. We previously synthesized a series of N-acyl amino acids (NAAAs) that inhibit the glycine transporter, GlyT2, some of which are also positive allosteric modulators of glycine receptors (GlyRs). In this study, we have synthesized a library of NAAAs that contain a phenylene ring within the acyl tail with the objective of improving efficacy at both GlyT2 and GlyRs and also identifying compounds that are efficacious as dual-acting modulators to enhance glycine neurotransmission. The most efficacious positive allosteric modulator of GlyRs was 2-[8-(2-octylphenyl)octanoylamino]acetic acid (8-8 OPGly) which potentiates the EC5 for glycine activation of GlyRα1 by 1500% with an EC50 of 664 nM. Phenylene-containing NAAAs with a lysine headgroup were the most potent inhibitors of GlyT2 with (2S)-6-amino-2-[8-(3-octylphenyl)octanoylamino]hexanoic acid (8-8 MPLys) inhibiting GlyT2 with an IC50 of 32 nM. The optimal modulator across both proteins was (2S)-6-amino-2-[8-(2-octylphenyl)octanoylamino]hexanoic acid (8-8 OPLys), which inhibits GlyT2 with an IC50 of 192 nM and potentiates GlyRs by up to 335% at 1 µM. When tested in a dual GlyT2/GlyRα1 expression system, 8-8 OPLys caused the greatest reductions in the EC50 for glycine. This suggests that the synergistic effects of a dual-acting modulator cause greater enhancements in glycinergic activity compared to single-target modulators and may provide an alternate approach to the development of new non-opioid analgesics for the treatment of chronic pain.

Carbon 14 synthesis of glycine transporter 1 inhibitor Iclepertin (BI 425809) and its major metabolites.

Carbon 14 labeled Iclepertin (BI 425809, 1) and its major metabolites were needed for ADME and several other studies necessary for the advancement of this drug candidate in clinical trials. Iclepertin is composed of two main chemical blocks, (R)-5-(methylsulfonyl)-2-([1,1,1-trifluoropropan-2-yl]oxy)benzoic acid (2), and 3-[(1R,5R)-3-azabicyclo[3.1.0]hexan-5-yl]-5-(trifluoromethyl)isoxazole (3) linked to each other via an amide bond. In the first synthesis of carbon 14 labeled 1, 2-fluorobenzoic acid, carboxyl-14 C was converted to [14 C]-2 in three steps and then coupled to 3 to provide [14 C]-1a in 45% overall yield. In the second synthesis, [14 C]-3 was prepared in six radioactive steps and coupled to the acid 2 to furnish [14 C]-1b in 20% overall yield. Both synthetic routes provided [14 C]-1a and [14 C]-1b with specific activities higher than 53 mCi/mmol and radiochemical, chemical, and enantiomeric purities above 98%. Two major metabolites of 1, BI 761036 and BI 758790, were also prepared labeled with carbon 14 using intermediates already available from the synthesis of [14 C]-1.

Synaptic Targets of Glycinergic Neurons in Laminae I-III of the Spinal Dorsal Horn.

A great deal of evidence supports the inevitable importance of spinal glycinergic inhibition in the development of chronic pain conditions. However, it remains unclear how glycinergic neurons contribute to the formation of spinal neural circuits underlying pain-related information processing. Thus, we intended to explore the synaptic targets of spinal glycinergic neurons in the pain processing region (laminae I-III) of the spinal dorsal horn by combining transgenic technology with immunocytochemistry and in situ hybridization accompanied by light and electron microscopy. First, our results suggest that, in addition to neurons in laminae I-III, glycinergic neurons with cell bodies in lamina IV may contribute substantially to spinal pain processing. On the one hand, we show that glycine transporter 2 immunostained glycinergic axon terminals target almost all types of excitatory and inhibitory interneurons identified by their neuronal markers in laminae I-III. Thus, glycinergic postsynaptic inhibition, including glycinergic inhibition of inhibitory interneurons, must be a common functional mechanism of spinal pain processing. On the other hand, our results demonstrate that glycine transporter 2 containing axon terminals target only specific subsets of axon terminals in laminae I-III, including nonpeptidergic nociceptive C fibers binding IB4 and nonnociceptive myelinated A fibers immunoreactive for type 1 vesicular glutamate transporter, indicating that glycinergic presynaptic inhibition may be important for targeting functionally specific subpopulations of primary afferent inputs.

Functional crosstalk of the glycine transporter GlyT1 and NMDA receptors.

NMDA-type glutamate receptors (NMDARs) constitute one of the main glutamate (Glu) targets in the central nervous system and are involved in synaptic plasticity, which is the molecular substrate of learning and memory. Hypofunction of NMDARs has been associated with schizophrenia, while overstimulation causes neuronal death in neurodegenerative diseases or in stroke. The function of NMDARs requires coincidental binding of Glu along with other cellular signals such as neuronal depolarization, and the presence of other endogenous ligands that modulate their activity by allosterism. Among these allosteric modulators are zinc, protons and Gly, which is an obligatory co-agonist. These characteristics differentiate NMDARs from other receptors, and their structural bases have begun to be established in recent years. In this review we focus on the crosstalk between Glu and glycine (Gly), whose concentration in the NMDAR microenvironment is maintained by various Gly transporters that remove or release it into the medium in a regulated manner. The GlyT1 transporter is particularly involved in this task, and has become a target of great interest for the treatment of schizophrenia since its inhibition leads to an increase in synaptic Gly levels that enhances the activity of NMDARs. However, the only drug that has completed phase III clinical trials did not yield the expected results. Notwithstanding, there are additional drugs that continue to be investigated, and it is hoped that knowledge gained from the recently published 3D structure of GlyT1 may allow the rational design of more effective new drugs. This article is part of the Special Issue on "The receptor-receptor interaction as a new target for therapy".

Membrane cholesterol regulates inhibition and substrate transport by the glycine transporter, GlyT2.

Membrane cholesterol binds to and modulates the function of various SLC6 neurotransmitter transporters, including stabilizing the outward-facing conformation of the dopamine and serotonin transporters. Here, we investigate how cholesterol binds to GlyT2 (SLC6A5), modulates glycine transport rate, and influences bioactive lipid inhibition of GlyT2. Bioactive lipid inhibitors are analgesics that bind to an allosteric site accessible from the extracellular solution when GlyT2 adopts an outward-facing conformation. Using molecular dynamics simulations, mutagenesis, and cholesterol depletion experiments, we show that bioactive lipid inhibition of glycine transport is modulated by the recruitment of membrane cholesterol to a binding site formed by transmembrane helices 1, 5, and 7. Recruitment involves cholesterol flipping from its membrane orientation, and insertion of the 3' hydroxyl group into the cholesterol binding cavity, close to the allosteric site. The synergy between cholesterol and allosteric inhibitors provides a novel mechanism of inhibition and a potential avenue for the development of potent GlyT2 inhibitors as alternative therapeutics for the treatment of neuropathic pain and therapeutics that target other SLC6 transporters.

Botulinum toxin type A counteracts neuropathic pain by countering the increase of GlyT2 expression in the spinal cord of CCI rats.

Botulinum toxin type A (BoNT/A) is a potent toxin, acts by cleaving synaptosome-associated-protein-25 (SNAP-25) to regulate the release of the neural transmitter and shows analgesic effect in neuropathic pain. However, the mechanisms of BoNT/A actions involved in nociceptions remain unclear. Glycine transporter 2 (GlyT2) is an isoform of glycine transporters, which plays an important role in the regulation of glycinergic neurotransmission. Inhibition of GlyTs could decrease pain sensation in neuropathic pain, the role of GlyT2 in the analgesic effect of BoNT/A has not been studied yet. In our present study, we demonstrated that the protein levels of GlyT2 and SNAP-25 were upregulated in the spinal cord after the development of chronic constriction injury (CCI)-induced neuropathic pain. Intraplantar application of BoNT/A (20 U/kg) attenuated mechanical allodynia induced by CCI and downregulated GlyT2 expression in the spinal cord. The application of BoNT/A s also decreased the expression of GlyT2 in pheochromocytoma (PC12) cells. Moreover, intrathecal application of lentivirus-mediated GlyT2 reversed the antinociceptive effect of BoNT/A in CCI rats. These findings indicate that GlyT2 contributes to the antinociceptive effect of BoNT/A and suggest a novel mechanism underlying BoNT/A's antinociception action.

Glycine transporters in schizophrenia. A new hope or informational noise? / Transportery glicynowe w schizofrenii. Nowa nadzieja czy szum informacyjny?

Currently, we observe a huge number of publications describing the role of glycine transporter (GlyT1) inhibitors in schizophrenia treatment. The concept of application for these drugs derives from the glutamatergic theory of schizophrenia. This theory explains psychotic disturbances as the consequence of NMDA receptor functioning defect. The role of the mentioned receptor depends mostly on the presence of cofactors. One such cofactor is the simplest aminoacid, glycine. This amino acid affects the glycine-binding site, located on the NR1 subunit of NMDAR and enables activation of the receptor. Substances enhancing the access of glycine to the receptor could hypothetically improve neuroplasticity. Higher efficacy of these neuroplastic processes may protect from cognitive deterioration and negative symptoms in the course of schizophrenia. In this article we present a systematic review of current literature on the topic of GlyT1 inhibitors in schizophrenia treatment (the state of literature as of November 2019). Firstly, we described the preclinical reasons for glycine enhancement use. Next, we used CINAHL, EMBASE, EMCARE, Medline, PsycINFO, PubMed and Google Scholar databases to extract and analyze evidence from clinical trials. GlyT1 inhibitors seem to have a potential in searching for novel substances in the treatment of negative symptoms, but their capacity to reduce cognitive deficits is not evidenced. So far, the clinical efficacy of several substances was proven, including N-methylglycine (sarcosine), bitopertin and derivatives obtained with chemical synthesis. Some of these substances demonstrate a beneficial clinical effect, but the number of published reports in this area is disproportionate to the value of evidence.

Analysis of Binding Determinants for Different Classes of Competitive and Noncompetitive Inhibitors of Glycine Transporters.

Glycine transporters are interesting therapeutic targets as they play significant roles in glycinergic and glutamatergic systems. The search for new selective inhibitors of particular types of glycine transporters (GlyT-1 and GlyT-2) with beneficial kinetics is hampered by limited knowledge about the spatial structure of these proteins. In this study, a pool of homology models of GlyT-1 and GlyT-2 in different conformational states was constructed using the crystal structures of related transporters from the SLC6 family and the recently revealed structure of GlyT-1 in the inward-open state, in order to investigate their binding sites. The binding mode of the known GlyT-1 and GlyT-2 inhibitors was determined using molecular docking studies, molecular dynamics simulations, and MM-GBSA free energy calculations. The results of this study indicate that two amino acids, Gly373 and Leu476 in GlyT-1 and the corresponding Ser479 and Thr582 in GlyT-2, are mainly responsible for the selective binding of ligands within the S1 site. Apart from these, one pocket of the S2 site, which lies between TM3 and TM10, may also be important. Moreover, selective binding of noncompetitive GlyT-1 inhibitors in the intracellular release pathway is affected by hydrophobic interactions with Ile399, Met382, and Leu158. These results can be useful in the rational design of new glycine transporter inhibitors with desired selectivity and properties in the future.

Synergistic Control of Transmitter Turnover at Glycinergic Synapses by GlyT1, GlyT2, and ASC-1.

In addition to being involved in protein biosynthesis and metabolism, the amino acid glycine is the most important inhibitory neurotransmitter in caudal regions of the brain. These functions require a tight regulation of glycine concentration not only in the synaptic cleft, but also in various intracellular and extracellular compartments. This is achieved not only by confining the synthesis and degradation of glycine predominantly to the mitochondria, but also by the action of high-affinity large-capacity glycine transporters that mediate the transport of glycine across the membranes of presynaptic terminals or glial cells surrounding the synapses. Although most cells at glycine-dependent synapses express more than one transporter with high affinity for glycine, their synergistic functional interaction is only poorly understood. In this review, we summarize our current knowledge of the two high-affinity transporters for glycine, the sodium-dependent glycine transporters 1 (GlyT1; SLC6A9) and 2 (GlyT2; SLC6A5) and the alanine-serine-cysteine-1 transporter (Asc-1; SLC7A10).

Bupivacaine reduces GlyT1 expression by potentiating the p-AMPKα/BDNF signalling pathway in spinal astrocytes of rats.

Bupivacaine, a local anaesthetic, is widely applied in the epidural or subarachnoid space to clinically manage acute and chronic pain. However, the underlying mechanisms are complex and unclear. Glycine transporter 1 (GlyT1) in the spinal cord plays a critical role in various pathologic pain conditions. Therefore, we sought to determine whether bupivacaine exerts its analgesic effect by regulating GlyT1 expression and to determine the underlying mechanisms of regulation. Primary astrocytes prepared from the spinal cord of rats were treated with bupivacaine. The protein levels of GlyT1, brain-derived neurotrophic factor (BDNF) and phosphorylated adenosine 5'-monophosphate (AMP)-activated protein kinase α (p-AMPKα) were measured by western blotting or immunofluorescence. In addition, 7,8-dihydroxyflavone (7,8-DHF, BDNF receptor agonist) and AMPK shRNA were applied to verify the relationship between the regulation of GlyT1 by bupivacaine and the p-AMPKα/BDNF signalling pathway. After treatment with bupivacaine, GlyT1 expression was diminished in a concentration-dependent manner, while the expression of BDNF and p-AMPK was increased. Moreover, 7,8-DHF decreased GlyT1 expression, and AMPK knockdown suppressed the upregulation of BDNF expression by bupivacaine. Finally, we concluded that bupivacaine reduced GlyT1 expression in spinal astrocytes by activating the p-AMPKα/BDNF signalling pathway. These results provide a new mechanism for the analgesic effect of intrathecal bupivacaine in the treatment of acute and chronic pain.

Effects of Cytochrome P450 3A4 Induction and Inhibition on the Pharmacokinetics of BI 425809, a Novel Glycine Transporter 1 Inhibitor.

BACKGROUND AND OBJECTIVE: Increased glycine availability at the synaptic cleft may enhance N-methyl-D-aspartate receptor signalling and provide a promising therapeutic strategy for cognitive impairment associated with schizophrenia. These studies aimed to assess the pharmacokinetics of BI 425809, a potent glycine-transporter-1 inhibitor, when co-administered with a strong cytochrome P450 3A4 (CYP3A4) inhibitor (itraconazole) and inducer (rifampicin). METHODS: In vitro studies using recombinant CYPs, human liver microsomes, and human hepatocytes were conducted to determine the CYP isoforms responsible for BI 425809 metabolism. In addition, two open-label, fixed-treatment period, phase I studies in healthy male volunteers are described. Period 1: participants received oral BI 425809 25 mg (single dose) on day 1; period 2: participants received multiple doses, across 10 days, of oral itraconazole or rifampicin combined with a single dose of oral BI 425809 25 mg on day 4/7 of the itraconazole/rifampicin treatment, respectively. Pharmacokinetic and safety endpoints were assessed in the absence/presence of itraconazole/rifampicin and included area under the concentration-time curve (AUC) over the time interval 0-167 h (AUC0‒167; itraconazole), 0-168 h (AUC0‒168; rifampicin), or 0-infinity (AUC0-∞; rifampicin and itraconazole), maximum measured concentration (Cmax) of BI 425809, and adverse events. RESULTS: In vitro results suggested that CYP3A4 accounted for ≥ 90% of the metabolism of BI 425809. BI 425809 exposure (adjusted geometric mean ratio [%]) was higher in the presence of itraconazole (AUC0‒167: 265.3; AUC0-∞: 597.0; Cmax: 116.1) and lower in the presence of rifampicin (AUC0‒168: 10.3; AUC0-∞: 9.8; Cmax: 37.4) compared with BI 425809 alone. Investigational treatments were well tolerated. CONCLUSIONS: Systemic exposure of BI 425809 was altered in the presence of strong CYP3A4 modulators, corroborating in vitro results that CYP3A4 mediates a major metabolic pathway for BI 425809. TRIAL REGISTRATION NUMBER: NCT02342717 (registered on 15 January 2015) and NCT03082183 (registered on 10 March 2017).

Regulation of the Glycine Transporter GLYT1 by microRNAs.

The glycine transporter GLYT1 participates in inhibitory and excitatory neurotransmission by controlling the reuptake of this neuroactive substance from synapses. Over the past few years, microRNAs have emerged as potent negative regulators of gene expression. In this report, we investigate the possible regulation of GLYT1 by microRNAs. TargetScan software predicted the existence of multiple targets for microRNAs within the 3' UTR of the human GLYT1 (miR-7, miR-30, miR-96, miR-137 and miR-141), and as they are all conserved among mammalian orthologues, their effects on GLYT1 expression were determined experimentally. Dual reporter bioluminescent assays showed that only miR-96 and miR-137 down-regulated expression of the Renilla reporter fused to the 3' UTR of GLYT1. Mutations introduced into the target sequences blocked this inhibitory effect. Consistently, these two microRNAs downregulated the uptake of [3H]glycine into glial C6 cells, a cell line where GLYT1 is the main carrier for glycine. Moreover, the expression of endogenous GLYT1 in primary mixed cultures from rat spinal cord was decreased upon lentiviral expression of miR-96 and miR-137. Although the bulk of GLYT1 is glial, it is abundantly expressed in glycinergic neurons of the retina and in smaller amounts in glutamatergic neurons though the brain. Since miR-96 in the retina is strongly downregulated by light exposure, when rats were maintained in darkness for a few hours we observed a concomitant increase of GLYT1 expression, suggesting that at least miR-96 might be an important negative regulator of GLYT1 under physiological conditions.

Calcium-Dependent Regulation of the Neuronal Glycine Transporter GlyT2 by M2 Muscarinic Acetylcholine Receptors.

The neuronal glycine transporter GlyT2 modulates inhibitory glycinergic neurotransmission and plays a key role in regulating nociceptive signal progression. The cholinergic system acting through muscarinic acetylcholine receptors (mAChRs) also mediates important regulations of nociceptive transmission being the M2 subtype the most abundantly expressed in the spinal cord. Here we studied the effect of M2 mAChRs stimulation on GlyT2 function co-expressed in a heterologous system with negligible levels of muscarinic receptor activity. We found GlyT2 is down-regulated by carbachol in a calcium-dependent manner. Different components involved in cell calcium homeostasis were analysed to establish a role in the mechanism of GlyT2 inhibition. GlyT2 down-regulation by carbachol was increased by thapsigargin and reduced by internal store depletion, although calcium release from endoplasmic reticulum or mitochondria had a minor role on GlyT2 inhibition. Our results are consistent with a GlyT2 sensitivity to intracellular calcium mobilized by M2 mAChRs in the subcortical area of the plasma membrane. A crucial role of the plasma membrane sodium calcium exchanger NCX is proposed.

Glucose metabolic profiles evaluated by PET associated with molecular characteristic landscape of gastric cancer.

BACKGROUND: Although FDG-PET is widely used in cancer, its role in gastric cancer (GC) is still controversial due to variable [18F]fluorodeoxyglucose ([18F]FDG) uptake. Here, we sought to develop a genetic signature to predict high FDG-avid GC to plan individualized PET and investigate the molecular landscape of GC and its association with glucose metabolic profiles noninvasively evaluated by [18F]FDG-PET. METHODS: Based on a genetic signature, PETscore, representing [18F]FDG avidity, was developed by imaging data acquired from thirty patient-derived xenografts (PDX). The PETscore was validated by [18F]FDG-PET data and gene expression data of human GC. The PETscore was associated with genomic and transcriptomic profiles of GC using The Cancer Genome Atlas. RESULTS: Five genes, PLS1, PYY, HBQ1, SLC6A5, and NAT16, were identified for the predictive model for [18F]FDG uptake of GC. The PETscore was validated in independent PET data of human GC with qRT-PCR and RNA-sequencing. By applying PETscore on TCGA, a significant association between glucose uptake and tumor mutational burden as well as genomic alterations were identified. CONCLUSION: Our findings suggest that molecular characteristics are underlying the diverse metabolic profiles of GC. Diverse glucose metabolic profiles may apply to precise diagnostic and therapeutic approaches for GC.

Glycine Transporters and Receptors as Targets for Analgesics.

The suitability of modulating glycinergic neurotransmission for the treatment of inflammatory and chronic pain has gained widespread recognition, with glycine receptors (GlyRs) and glycine transporters (GlyT1 and GlyT2) now considered key therapeutic targets [...].

The presynaptic glycine transporter GlyT2 is regulated by the Hedgehog pathway in vitro and in vivo.

The identity of a glycinergic synapse is maintained presynaptically by the activity of a surface glycine transporter, GlyT2, which recaptures glycine back to presynaptic terminals to preserve vesicular glycine content. GlyT2 loss-of-function mutations cause Hyperekplexia, a rare neurological disease in which loss of glycinergic neurotransmission causes generalized stiffness and strong motor alterations. However, the molecular underpinnings controlling GlyT2 activity remain poorly understood. In this work, we identify the Hedgehog pathway as a robust controller of GlyT2 expression and transport activity. Modulating the activation state of the Hedgehog pathway in vitro in rodent primary spinal cord neurons or in vivo in zebrafish embryos induced a selective control in GlyT2 expression, regulating GlyT2 transport activity. Our results indicate that activation of Hedgehog reduces GlyT2 expression by increasing its ubiquitination and degradation. This work describes a new molecular link between the Hedgehog signaling pathway and presynaptic glycine availability.