Solomon H. Snyder

Catechol- O -methyltransferase connects dopamine homeostasis to redox signaling, metal homeostasis, and protein folding in schizophrenia

Dysregulated dopamine (DA) signaling and redox homeostasis contributes to multiple neuropsychiatric and neurodegenerative disorders. Polymorphisms that influence the activity of catechol-O-methyltransferase (COMT), an enzyme critical for degrading DA in the dorsolateral prefrontal cortex, have been implicated in behavioral and neuropsychiatric alterations associated with schizophrenia (SCZ). Adverse neuropsychiatric effects have also been reported in Parkinson’s disease (PD) patients administered COMT inhibitors in combination with other DA-enhancing therapies. COMT exists as two isoforms: a soluble short isoform (S-COMT) and a membrane-bound long isoform (MB-COMT). These variants differ in their N-terminal domains, with MB-COMT being the predominant brain isoform. Here, unbiased proteomic and biochemical analyses show that genetic loss of MB-COMT disrupts DA signaling and perturbs pathways governing synaptic and mitochondrial function, iron and copper homeostasis, and redox balance. Limited proteolysis mass spectrometry (LiP-MS) further revealed that MB-COMT deficiency triggers widespread protein structural alterations, a molecular event commonly occurring in neurodegenerative conditions but not as well studied in neuropsychiatric diseases. Our results show that MB-COMT is a molecular hub that connects multiple cellular pathways whose differential dysregulation underlies the pathophysiology of complex neuropsychiatric diseases such as SCZ. Thus, MB-COMT is identified as a key regulator of brain DA biology, loss of which activates cellular stress response pathways, revealing potential targets for therapeutic intervention.

Evolution of the ATLAS event data model for the HL-LHC

Evolving the event data model for efficient use of GPUs and FPGAs in high-luminosity LHC events, indicating improved data processing capabilities.

Biliverdin reductase A is a major determinant of protective NRF2 signaling

FCC feasibility studies: Impact of tracker- and calorimeter-detector performance on jet flavor identification and Higgs physics analyses

This analysis demonstrates how tracker and calorimeter performance affect jet flavor identification, suggesting improvements for Higgs physics studies.

Early Evidence of Safety, Clinical Benefit, and Pharmacokinetics of Roflumilast Cream 0.3% Once Daily for Treatment of Mild or Moderate Plaque Psoriasis in Children Aged 2–11 Years

Phase 2 trials demonstrate clinical benefit and pharmacokinetics of roflumilast cream in children with psoriasis, indicating safety.

Biliverdin Reductase A is a major determinant of neuroprotective Nrf2 signaling

Biliverdin reductase A (BVRA), the terminal enzyme in heme catabolism, generates the neuroprotective and lipophilic antioxidant bilirubin. Here, we identify a novel non-enzymatic role for BVRA in redox regulation. We show that BVRA directly interacts with nuclear factor erythroid-derived factor-like 2 (Nrf2), the master regulator of redox homeostasis, to modulate target signaling pathways. ChIP-seq and RNA-seq analyses reveal that this interaction coordinates the expression of neuroprotective genes that are typically dysregulated in Alzheimer's disease and other neurodegenerative conditions. Thus, this previously unknown BVRA-Nrf2 axis controls an essential pathway of redox signaling in neuroprotection. Our findings establish BVRA as a dual-function integrator of antioxidant defenses in both the lipophilic and hydrophilic subcellular compartments, bridging these two distinct and critical cellular protection mechanisms in the brain. This advancement in understanding the endogenous antioxidant system of the brain positions the BVRA-Nrf2 axis as a promising therapeutic target for neurodegenerative disease. Significance Statement: We show a non-canonical role for biliverdin reductase A (BVRA), classically known as the biosynthetic enzyme for bilirubin, in nonenzymatic modulation of antioxidant neuroprotective nuclear factor erythroid-derived factor-like 2 (Nrf2) signaling in the brain. Both BVRA and Nrf2 signaling are compromised in neurodegenerative diseases such as Alzheimer's disease, and the BVRA-Nrf2 axis offers a new direction for developing neuroprotective therapies.

Mammalian D-Cysteine controls insulin secretion in the pancreas

D-amino acids are being recognized as important molecules in mammals with function. This is a first identification of endogenous D-cysteine in mammalian pancreas. Using a novel stereospecific bioluminescent assay, chiral chromatography, enzyme kinetics and a transgenic mouse model we identify endogenous D-cysteine. We elucidate its function in two mice models of type 1 diabetes (STZ and NOD), and in tests of Glucose Stimulated Insulin Secretion in isolated mouse and human islets and INS-1 832/13 cell line. D-cysteine is synthesized by serine racemase (SR) and SR −/− mice produce 6–10 fold higher levels of insulin in the pancreas and plasma including higher glycogen and ketone bodies in the liver. The excess insulin is stored as amyloid in secretory vesicles and exosomes. In glucose stimulated insulin secretion in mouse and human islets, equimolar amount of D-cysteine showed higher inhibition of insulin secretion compared to D-serine, another closely related stereoisomer synthesized by SR. In mouse models of diabetes (Streptozotocin (STZ) and Non Obese Diabetes (NOD) and human pancreas, the diabetic state showed increased expression of D-cysteine compared to D-serine followed by increased expression of SR. SR −/− mice show decreased cAMP in the pancreas, lower DNA methyltransferase enzymatic and promoter activities followed by reduced phosphorylation of CREB (S133), resulting in decreased methylation of the Ins1 promoter. D-cysteine is efficiently metabolized by D-amino acid oxidase and transported by ASCT2 and Asc1. Dietary supplementation with methyl donors restored the high insulin levels and low DNMT enzymatic activity in SR −/− mice. Our data show that endogenous D-cysteine in the mammalian pancreas is a regulator of insulin secretion. • Serine Racemase (SR) is also a cysteine racemase. • Lack of SR results in high levels of insulin in the pancreas and plasma. • D-cysteine shows greater inhibition of insulin secretion compared to D-serine. • Endogenous D-cysteine signals via cyclic AMP mediated by CREB-DNMT1 interaction. • Hypomethylation of Ins1 promoter is rescued by high methyl donor diet rescuing high insulin levels.

Inositol Pyrophosphates as Versatile Metabolic Messengers

Discovered in 1993, inositol pyrophosphates are evolutionarily conserved signaling metabolites whose versatile modes of action are being increasingly appreciated. These include their emerging roles as energy regulators, phosphodonors, steric/allosteric regulators, and G protein–coupled receptor messengers. Through studying enzymes that metabolize inositol pyrophosphates, progress has also been made in elucidating the various cellular and physiological functions of these pyrophosphate-containing, energetic molecules. The two main forms of inositol pyrophosphates, 5-IP 7 and IP 8 , synthesized respectively by inositol-hexakisphosphate kinases (IP6Ks) and diphosphoinositol pentakisphosphate kinases (PPIP5Ks), regulate phosphate homeostasis, ATP synthesis, and several other metabolic processes ranging from insulin secretion to cellular energy utilization. Here, we review the current understanding of the catalytic and regulatory mechanisms of IP6Ks and PPIP5Ks, as well as their counteracting phosphatases. We also highlight the genetic and cellular evidence implicating inositol pyrophosphates as essential mediators of mammalian metabolic homeostasis.

640 - Investigator- and patient-rated local tolerability in phase 3 trials of topical roflumilast in patients with psoriasis, seborrheic dermatitis, and atopic dermatitis

Background Formulating a topical medication that does not irritate the skin is an important factor contributing to patient treatment adherence and satisfaction. Many topical prescription products use penetration enhancers (including propylene glycol, polyethylene glycol, and ethanol) to overcome barrier properties of the skin. However, these excipients may irritate the skin causing tolerability reactions such as burning and stinging, which can reduce patient treatment adherence. Topical roflumilast is a highly potent (Kd∼0.7 nM) phosphodiesterase 4 inhibitor formulated as a water-based cream or foam that does not contain penetration enhancers or fragrances. Objective We present prospectively assessed investigator- and patient-rated local tolerability from Phase 3 trials of topical roflumilast for patients with psoriasis (DERMIS-1, DERMIS-2, ARRECTOR), seborrheic dermatitis (SD; STRATUM), and atopic dermatitis (AD; INTEGUMENT-1, INTEGUMENT-2). Methods Patients were randomized to apply topical roflumilast (DERMIS: 0.3% cream; ARRECTOR and STRATUM: 0.3% foam; INTEGUMENT: 0.15% cream) or vehicle once daily for 8 weeks (DERMIS, ARRECTOR, and STRATUM) or 4 weeks (INTEGUMENT). Investigators assessed local tolerability on an 8-point scale (0 [no evidence of irritation] to 7 [strong reaction spreading beyond application site]) in the clinic before investigational product (IP) application. Patients reported local tolerability on a 4-point scale (0 [none: no sensation] to 3 [severe: hot, tingling/stinging sensation that has caused definite discomfort]) in the clinic 10-15 minutes after IP application. Tolerability was also assessed by reviewing documented adverse events. Results As assessed by investigators, ≥96.5% of patients in the roflumilast-treated groups had no evidence of irritation at the application site across all trials at all timepoints. Patient-rated local tolerability was favorable and improved with treatment: across all trials, 1% of roflumilast-treated patients reported a score of 3 (severe; defined as a “hot tingling/stinging sensation that has caused definite discomfort”) after the first application (day 1) and <1% at each subsequent assessment. Rates of adverse events, including those at the application site, were low for all trials. Conclusions Roflumilast cream and foam formulations demonstrated favorable local tolerability based on investigator- and patient-rated assessments in patients with psoriasis, SD, and AD, including application to sensitive areas such as the face and intertriginous areas.

Inositol polyphosphate multikinase modulates redox signaling through nuclear factor erythroid 2-related factor 2 and glutathione metabolism

Maintenance of redox balance plays central roles in a plethora of signaling processes. Although physiological levels of reactive oxygen and nitrogen species are crucial for functioning of certain signaling pathways, excessive production of free radicals and oxidants can damage cell components. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling cascade is the key pathway that mediates cellular response to oxidative stress. It is controlled at multiple levels, which serve to maintain redox homeostasis within cells. We show here that inositol polyphosphate multikinase (IPMK) is a modulator of Nrf2 signaling. IPMK binds Nrf2 and attenuates activation and expression of Nrf2 target genes. Furthermore, depletion of IPMK leads to elevated glutathione and cysteine levels, resulting in increased resistance to oxidants. Accordingly, targeting IPMK may restore redox balance under conditions of cysteine and glutathione insufficiency.

Serine Racemase mediates subventricular zone neurogenesis via fatty acid metabolism

The adult subventricular zone (SVZ) is a neurogenic niche that continuously produces newborn neurons. Here we show that serine racemase (SR), an enzyme that catalyzes the racemization of L-serine to D-serine and vice versa, affects neurogenesis in the adult SVZ by controlling de novo fatty acid synthesis. Germline and conditional deletion of SR (nestin precursor cells) leads to diminished neurogenesis in the SVZ. Nestin-cre+ mice showed reduced expression of fatty acid synthase and its substrate malonyl-CoA, which are involved in de novo fatty acid synthesis. Global lipidomic analyses revealed significant alterations in different lipid subclasses in nestin-cre+ mice. Decrease in fatty acid synthesis was mediated by phospho Acetyl-CoA Carboxylase that was AMP-activated protein kinase independent. Both L- and D-serine supplementation rescued defects in SVZ neurogenesis, proliferation, and levels of malonyl-CoA in vitro. Our work shows that SR affects adult neurogenesis in the SVZ via lipid metabolism.

Identification of the NRF2 transcriptional network as a therapeutic target for trigeminal neuropathic pain

Trigeminal neuralgia, historically dubbed the "suicide disease," is an exceedingly painful neurologic condition characterized by sudden episodes of intense facial pain. Unfortunately, the only U.S. Food and Drug Administration (FDA)-approved medication for trigeminal neuralgia carries substantial side effects, with many patients requiring surgery. Here, we identify the NRF2 transcriptional network as a potential therapeutic target. We report that cerebrospinal fluid from patients with trigeminal neuralgia accumulates reactive oxygen species, several of which directly activate the pain-transducing channel TRPA1. Similar to our patient cohort, a mouse model of trigeminal neuropathic pain also exhibits notable oxidative stress. We discover that stimulating the NRF2 antioxidant transcriptional network is as analgesic as inhibiting TRPA1, in part by reversing the underlying oxidative stress. Using a transcriptome-guided drug discovery strategy, we identify two NRF2 network modulators as potential treatments. One of these candidates, exemestane, is already FDA-approved and may thus be a promising alternative treatment for trigeminal neuropathic pain.

Mutant Huntingtin Derails Cysteine Metabolism in Huntington’s Disease at Both Transcriptional and Post-Translational Levels

Cysteine is a semi-essential amino acid that not only plays an essential role as a component of protein synthesis, but also in the generation of numerous sulfur-containing molecules such as the antioxidant glutathione and coenzyme A. We previously showed that the metabolism of cysteine is dysregulated in Huntington's disease (HD), a neurodegenerative disorder triggered by the expansion of polyglutamine repeats in the protein huntingtin. In this study, we showed that cysteine metabolism is compromised at multiple levels in HD, both transcriptional and post-translational. Accordingly, restoring cysteine homeostasis may be beneficial in HD.

Serine Racemase mediates Subventricular Zone Neurogenesis via Fatty acid Metabolism

Summary The adult subventricular zone is one of the two neurogenic niches that continuously produce newborn neurons. Here we show that serine racemase (SR), an enzyme that catalyzes the racemization of L-serine to D-serine and vice versa, affects neurogenesis in the adult SVZ by controlling de novo fatty acid synthesis. Complete and conditional deletion of SR in nestin precursor cells lead to diminished neurogenesis in the SVZ. Nestin-cre+ mice showed reduced expression of fatty acid synthase and its substrate malonyl CoA, which are involved in de novo fatty acid synthesis. Global lipidomic analyses revealed significant alterations in lipid subclasses in nestin-cre+ mice. Decrease in fatty acid synthesis was mediated by phospho acetyl CoA carboxylase that was AMPK independent. Both L and D serine treatment rescued defects in SVZ neurogenesis, proliferation and levels of malonyl CoA in vitro . Our work shows that SR affects adult neurogenesis in the SVZ via lipid metabolism.

Mammalian D-Cysteine controls insulin secretion in the pancreas

D-amino acids are being recognized in mammals as important molecules with function. This is a first identification of endogenous D-cysteine in mammalian pancreas. D-cysteine is synthesized by serine racemase (SR) and SR −/− mice produce 6-10 fold higher levels of insulin in the pancreas and plasma including higher glycogen and ketone bodies in the liver. The excess insulin is stored as amyloid in secretory vesicles and exosomes. In glucose stimulated insulin secretion studies in mouse and human islets, equimolar amount of D-cysteine showed higher inhibition of insulin secretion compared to D-serine, another closely related stereoisomer synthesized by SR. In mouse models of diabetes (STZ and NOD) and human pancreas, the diabetic state showed increased expression of D-cysteine compared to D-serine followed by increased expression of SR. SR −/− mice show decreased cAMP in the pancreas followed by reduced phosphorylation of CREB (S133), lower DNA methyltransferase enzymatic and promoter activities resulting in decreased methylation of the Ins1 promoter. D-cysteine is efficiently metabolized by D-amino acid oxidase and transported by ASCT2 and Asc1. Dietary supplementation with methyl donors restored the high insulin levels and low DNMT enzymatic activity in SR −/− mice. Our data show that endogenous D-cysteine in the mammalian pancreas is a regulator of insulin secretion. Highlights Serine Racemase also functions as a cysteine racemase. Lack of Serine Racemase results in significantly high levels of insulin in the pancreas, plasma and larger islets. D-cysteine shows greater inhibition of insulin secretion compared to D-serine. Endogenous D-cysteine signals via cyclic AMP that mediates downstream CREB-DNMT1 interaction. CREB-DNMT1 interaction results in hypomethylation of Ins1 promoter that can be rescued by high methyl donor dietary supplementation rescuing high insulin levels.

Biliverdin reductase bridges focal adhesion kinase to Src to modulate synaptic signaling

Synapses connect discrete neurons into vast networks that send, receive, and encode diverse forms of information. Synaptic function and plasticity, the neuronal process of adapting to diverse and variable inputs, depend on the dynamic nature of synaptic molecular components, which is mediated in part by cell adhesion signaling pathways. Here, we found that the enzyme biliverdin reductase (BVR) physically links together key focal adhesion signaling molecules at the synapse. BVR -null ( BVR −/− ) mice exhibited substantial deficits in learning and memory on neurocognitive tests, and hippocampal slices in which BVR was postsynaptically depleted showed deficits in electrophysiological responses to stimuli. RNA sequencing, biochemistry, and pathway analyses suggested that these deficits were mediated through the loss of focal adhesion signaling at both the transcriptional and biochemical level in the hippocampus. Independently of its catalytic function, BVR acted as a bridge between the primary focal adhesion signaling kinases FAK and Pyk2 and the effector kinase Src. Without BVR, FAK and Pyk2 did not bind to and stimulate Src, which then did not phosphorylate the N -methyl- d -aspartate (NMDA) receptor, a critical posttranslational modification for synaptic plasticity. Src itself is a molecular hub on which many signaling pathways converge to stimulate NMDAR-mediated neurotransmission, thus positioning BVR at a prominent intersection of synaptic signaling.

Mammalian D‐cysteine: A novel regulator of neural progenitor cell proliferation

D-amino acids are being recognized as functionally important molecules in mammals. We recently identified endogenous D-cysteine in mammalian brain. D-cysteine is present in neonatal brain in substantial amounts (mM) and decreases with postnatal development. D-cysteine binds to MARCKS and a host of proteins implicated in cell division and neurodevelopmental disorders. D-cysteine decreases phosphorylation of MARCKS in neural progenitor cells (NPCs) affecting its translocation. D-cysteine controls NPC proliferation by inhibiting AKT signaling. Exogenous D-cysteine inhibits AKT phosphorylation at Thr 308 and Ser 473 in NPCs. D-cysteine treatment of NPCs led to 50% reduction in phosphorylation of Foxo1 at Ser 256 and Foxo3a at Ser 253. We hypothesize that in the developing brain endogenous D-cysteine is as a physiologic regulator of NPC proliferation by inhibiting AKT signaling mediated by Foxo1 and Foxo3a. Endogenous D-cysteine may regulate mammalian neurodevelopment with roles in schizophrenia and Alzheimer's disease (AD).

A high-affinity cocaine binding site associated with the brain acid soluble protein 1

Cocaine exerts its stimulant effect by inhibiting dopamine (DA) reuptake, leading to increased dopamine signaling. This action is thought to reflect the binding of cocaine to the dopamine transporter (DAT) to inhibit its function. However, cocaine is a relatively weak inhibitor of DAT, and many DAT inhibitors do not share cocaine’s behavioral actions. Further, recent reports show more potent actions of the drug, implying the existence of a high-affinity receptor for cocaine. We now report high-affinity binding of cocaine associated with the brain acid soluble protein 1 (BASP1) with a dissociation constant (Kd) of 7 nM. Knocking down BASP1 in the striatum inhibits [3H]cocaine binding to striatal synaptosomes. Depleting BASP1 in the nucleus accumbens but not the dorsal striatum diminishes locomotor stimulation in mice. Our findings imply that BASP1 is a pharmacologically relevant receptor for cocaine.

Inositol hexakisphosphate kinase-2 non-catalytically regulates mitophagy by attenuating PINK1 signaling

Inositol pyrophosphates, such as 5-diphosphoinositol pentakisphosphate (IP7), are generated by a family of inositol hexakisphosphate kinases (IP6Ks), of which IP6K2 has been implicated in various cellular functions including neuroprotection. Absence of IP6K2 causes impairment of oxidative phosphorylation regulated by creatine kinase-B. In the present study, we show that IP6K2 is involved in attenuation of PINK1-mediated mitochondrial autophagy (mitophagy) in the brain. Up-regulation of dynamin-related protein (Drp-1), as well as increased expression of mitochondrial biogenesis markers (PGC1-α and NRF-1) in the cerebella of IP6K2-deleted mice (IP6K2-knockout), point to the involvement of IP6K2 in the regulation of mitochondrial fission. Knockdown of IP6K2 also leads to augmented glycolysis, potentially as a compensatory mechanism for decreased mitochondrial respiration. Overexpressing IP6K2 as well as IP6K2-kinase dead mutant in IP6K2-knockdown N2A cells reverses the expression of mitophagy markers, demonstrating that IP6K2-induced mitoprotection is catalytically/kinase independent. IP6K2 supplementation in K2-PINK1 double-knockdown N2A cells fails to reverse the expression of the mitophagic marker, LC3-II, indicating that the mitoprotective effect of IP6K2 is dependent on PINK1. Overall, our study reveals a key neuroprotective role of IP6K2 in the prevention of PINK1-mediated mitophagy in the brain.

D-cysteine is an endogenous regulator of neural progenitor cell dynamics in the mammalian brain

-methyl-d-aspartate (NMDA) glutamate receptor coagonist d-serine, as a candidate biosynthetic enzyme for d-cysteine. d-cysteine is enriched more than 20-fold in the embryonic mouse brain compared with the adult brain. d-cysteine reduces the proliferation of cultured mouse embryonic neural progenitor cells (NPCs) by ∼50%, effects not shared with d-serine or l-cysteine. The antiproliferative effect of d-cysteine is mediated by the transcription factors FoxO1 and FoxO3a. The selective influence of d-cysteine on NPC proliferation is reflected in overgrowth and aberrant lamination of the cerebral cortex in neonatal SR knockout mice. Finally, we perform an unbiased screen for d-cysteine-binding proteins in NPCs by immunoprecipitation with a d-cysteine-specific antibody followed by mass spectrometry. This approach identifies myristoylated alanine-rich C-kinase substrate (MARCKS) as a putative d-cysteine-binding protein. Together, these results establish endogenous mammalian d-cysteine and implicate it as a physiologic regulator of NPC homeostasis in the developing brain.