Pro-atherogenic medical conditions are associated with widespread regional brain metabolite abnormalities in those with alcohol use disorder.

AIMS: Widespread brain metabolite abnormalities in those with alcohol use disorder (AUD) were reported in numerous studies, but the effects of the pro-atherogenic conditions of hypertension, type 2 diabetes mellitus, hepatitis C seropositivity, and hyperlipidemia on metabolite levels were not considered. These conditions were associated with brain metabolite abnormalities in those without AUD. We predicted treatment-seeking individuals with AUD and pro-atherogenic conditions (Atherogenic+) demonstrate lower regional metabolite markers of neuronal viability [N-acetylaspartate (NAA)] and cell membrane turnover/synthesis [choline-containing compounds (Cho)], compared with those with AUD without pro-atherogenic conditions (Atherogenic-) and healthy controls (CON). METHODS: Atherogenic+ (n = 59) and Atherogenic- (n = 51) and CON (n = 49) completed a 1.5 T proton magnetic resonance spectroscopic imaging study. Groups were compared on NAA, Cho, total creatine, and myoinositol in cortical gray matter (GM), white matter (WM), and select subcortical regions. RESULTS: Atherogenic+ had lower frontal GM and temporal WM NAA than CON. Atherogenic+ showed lower parietal GM, frontal, parietal and occipital WM and lenticular nuclei NAA level than Atherogenic- and CON. Atherogenic- showed lower frontal GM and WM NAA than CON. Atherogenic+ had lower Cho level than CON in the frontal GM, parietal WM, and thalamus. Atherogenic+ showed lower frontal WM and cerebellar vermis Cho than Atherogenic- and CON. CONCLUSIONS: Findings suggest proatherogenic conditions in those with AUD were associated with increased compromise of neuronal integrity and cell membrane turnover/synthesis. The greater metabolite abnormalities observed in Atherogenic+ may relate to increased oxidative stress-related compromise of neuronal and glial cell structure and/or impaired arterial vasoreactivity/lumen viability.

In silico approaches to study the human asparagine synthetase: An insight of the interaction between the enzyme active sites and its substrates.

Cancer is a leading concern and important cause of death worldwide. Cancer is a non-communicable illness defined as uncontrolled division of cells. It can develop into metastatic cancer when tumor cells migrate to other organs. In recent years evidence has emerged that the bioavailability of Asn play a crucial role in cancer metastasis. Asn is a non-essential amino acid formed from an ATP dependent catalyzed reaction by the enzyme asparagine synthetase (ASNS), where Asp and Gln are converted to Asn and Glu, respectively. The human ASNS enzyme consist of 561 amino acids, with a molecular weight of 64 KDa. ASNS governs the activation of transcriptional factors that regulate the process of metastasis. In this work the 3D model of ASNS in E. coli (AS-B) and the human ASNS docked with its different ligands have been used to study the 3D mechanism of the conversion of Asp and Gln to Asn and Glu, in human ASNS. The stability evaluation of the docked complexes was checked by molecular dynamic simulation through the bioinformatic tool Desmond. The binding residues and their interactions can be exploited for the development of inhibitors, as well as for finding new drug molecules against ASNS and prevention of metastatic cancer.

Cumulative asparagine to aspartate deamidation fails to perturb γD-crystallin structure and stability.

Deamidation frequently is invoked as an important driver of crystallin aggregation and cataract formation. Here, we characterized the structural and biophysical consequences of cumulative Asn to Asp changes in γD-crystallin. Using NMR spectroscopy, we demonstrate that N- or C-terminal domain-confined or fully Asn to Asp changed γD-crystallin exhibits essentially the same 1H-15N HSQC spectrum as the wild-type protein, implying that the overall structure is retained. Only a very small thermodynamic destabilization for the overall Asn to Asp γD-crystallin variants was noted by chaotropic unfolding, and assessment of the colloidal stability, by measuring diffusion interaction parameters, yielded no substantive differences in association propensities. Furthermore, using molecular dynamics simulations, no significant changes in dynamics for proteins with Asn to Asp or iso-Asp changes were detected. Our combined results demonstrate that substitution of all Asn by Asp residues, reflecting an extreme case of deamidation, did not affect the structure and biophysical properties of γD-crystallin. This suggests that these changes alone cannot be the major determinant in driving cataract formation.

Synthesis of aspartic acid and tyrosine by the fire blight pathogen Erwinia amylovora is not required for proliferation on apple flower stigmas or virulence in fruitlets.

AIMS: The Gram-negative bacterium Erwinia amylovora (Ea) is the causal agent of fire blight, a devastating disease of apples and pears. In the fire blight disease cycle, Ea grows in different plant tissues, each presenting a distinct nutrient environment. Here, we investigate the ability of aspartate and tyrosine double auxotroph Ea lines to proliferate on apple flower stigma surfaces representing the epiphytic growth stage of Ea and in developing fruitlets representing one endophytic growth stage of Ea. METHODS AND RESULTS: Heterologous complementation studies in an Escherichia coli aspartate and tyrosine auxotroph verify that Ea aspartate aminotransferase (AspC) and tyrosine aminotransferase (TyrB) act as aspartate and tyrosine amino transferases. Growth analysis reveals that Ea aspC tyrB mutants multiply to near-wild-type levels on apple flower stigmas and immature fruitlets. CONCLUSIONS: Ea AspC and TyrB are reciprocally complementing for aspartate and tyrosine synthesis in Ec and in Ea. Ea aspC  and  tyrB mutants obtain sufficient aspartate and tyrosine to support multiplication on stigma surfaces and virulence in immature fruitlets.

Aspartate aminotransferase of Rhizobium leguminosarum has extended substrate specificity and metabolizes aspartate to enable N2 fixation in pea nodules.

Rhizobium leguminosarum aspartate aminotransferase (AatA) mutants show drastically reduced symbiotic nitrogen fixation in legume nodules. Whilst AatA reversibly transaminates the two major amino-donor compounds aspartate and glutamate, the reason for the lack of N2 fixation in the mutant has remained unclear. During our investigations into the role of AatA, we found that it catalyses an additional transamination reaction between aspartate and pyruvate, forming alanine. This secondary reaction runs at around 60 % of the canonical aspartate transaminase reaction rate and connects alanine biosynthesis to glutamate via aspartate. This may explain the lack of any glutamate-pyruvate transaminase activity in R. leguminosarum, which is common in eukaryotic and many prokaryotic genomes. However, the aspartate-to-pyruvate transaminase reaction is not needed for N2 fixation in legume nodules. Consequently, we show that aspartate degradation is required for N2 fixation, rather than biosynthetic transamination to form an amino acid. Hence, the enzyme aspartase, which catalyses the breakdown of aspartate to fumarate and ammonia, suppressed an AatA mutant and restored N2 fixation in pea nodules.

Amplifying hepatic L-aspartate levels suppresses CCl4-induced liver fibrosis by reversing glucocorticoid receptor ß-mediated mitochondrial malfunction.

Liver fibrosis is a determinant-stage process of many chronic liver diseases and affected over 7.9 billion populations worldwide with increasing demands of ideal therapeutic agents. Discovery of active molecules with anti-hepatic fibrosis efficacies presents the most attacking filed. Here, we revealed that hepatic L-aspartate levels were decreased in CCl4-induced fibrotic mice. Instead, supplementation of L-aspartate orally alleviated typical manifestations of liver injury and fibrosis. These therapeutic efficacies were alongside improvements of mitochondrial adaptive oxidation. Notably, treatment with L-aspartate rebalanced hepatic cholesterol-steroid metabolism and reduced the levels of liver-impairing metabolites, including corticosterone (CORT). Mechanistically, L-aspartate treatment efficiently reversed CORT-mediated glucocorticoid receptor ß (GRß) signaling activation and subsequent transcriptional suppression of the mitochondrial genome by directly binding to the mitochondrial genome. Knockout of GRß ameliorated corticosterone-mediated mitochondrial dysfunction and hepatocyte damage which also weakened the improvements of L-aspartate in suppressing GRß signaling. These data suggest that L-aspartate ameliorates hepatic fibrosis by suppressing GRß signaling via rebalancing cholesterol-steroid metabolism, would be an ideal candidate for clinical liver fibrosis treatment.

Biochemical characterization of l-asparagine synthetase from Streptococcus thermophilus and its application in the enzymatic synthesis of ß-aspartyl compounds.

ß-Aspartyl compounds, such as ß-aspartyl hydroxamate (serine racemase inhibitor), ß-aspartyl-l-lysine (moisture retention), and ß-aspartyl-l-tryptophan (immunomodulator) are physiologically active compounds. There is limited literature on the development of effective methods of production of ß-aspartyl compounds. In this study, we describe the biochemical characterization of asparagine synthetase (AS) from Streptococcus thermophilus NBRC 13957 (StAS) and the enzymatic synthesis of ß-aspartyl compounds using StAS. Recombinant StAS was expressed in Escherichia coli BL21(DE3) and it displayed activity towards hydroxylamine, methylamine, ethylamine, and ammonia, as acceptors of the ß-aspartyl moiety. StAS exhibited higher activity toward hydroxylamine and ethylamine as acceptor substrates compared with the enzymes from Lactobacillus delbrueckii NBRC 13953, Lactobacillus reuteri NBRC 15892, and E. coli. The coupling of the synthesis of ß-aspartyl compounds by StAS with an ATP-regeneration system using polyphosphate kinase from Deinococcus proteoliticus NBRC 101906 displayed an approximately 2.5-fold increase in the production of ß-aspartylhydroxamate from 1.06 mM to 2.53 mM after a 76-h reaction.

Retrospective analysis of Braak stage- and APOE4 allele-dependent associations between MR spectroscopy and markers of tau and neurodegeneration in cognitively unimpaired elderly.

PURPOSE: The pathological hallmarks of Alzheimer's disease (AD), amyloid, tau, and associated neurodegeneration, are present in the cortical gray matter (GM) years before symptom onset, and at significantly greater levels in carriers of the apolipoprotein E4 (APOE4) allele. Their respective biomarkers, A/T/N, have been found to correlate with aspects of brain biochemistry, measured with magnetic resonance spectroscopy (MRS), indicating a potential for MRS to augment the A/T/N framework for staging and prediction of AD. Unfortunately, the relationships between MRS and A/T/N biomarkers are unclear, largely due to a lack of studies examining them in the context of the spatial and temporal model of T/N progression. Advanced MRS acquisition and post-processing approaches have enabled us to address this knowledge gap and test the hypotheses, that glutamate-plus-glutamine (Glx) and N-acetyl-aspartate (NAA), metabolites reflecting synaptic and neuronal health, respectively, measured from regions on the Braak stage continuum, correlate with: (i) cerebrospinal fluid (CSF) p-tau181 level (T), and (ii) hippocampal volume or cortical thickness of parietal lobe GM (N). We hypothesized that these correlations will be moderated by Braak stage and APOE4 genotype. METHODS: We conducted a retrospective imaging study of 34 cognitively unimpaired elderly individuals who received APOE4 genotyping and lumbar puncture from pre-existing prospective studies at the NYU Grossman School of Medicine between October 2014 and January 2019. Subjects returned for their imaging exam between April 2018 and February 2020. Metabolites were measured from the left hippocampus (Braak II) using a single-voxel semi-adiabatic localization by adiabatic selective refocusing sequence; and from the bilateral posterior cingulate cortex (PCC; Braak IV), bilateral precuneus (Braak V), and bilateral precentral gyrus (Braak VI) using a multi-voxel echo-planar spectroscopic imaging sequence. Pearson and Spearman correlations were used to examine the relationships between absolute levels of choline, creatine, myo-inositol, Glx, and NAA and CSF p-tau181, and between these metabolites and hippocampal volume or parietal cortical thicknesses. Covariates included age, sex, years of education, Fazekas score, and months between CSF collection and MRI exam. RESULTS: There was a direct correlation between hippocampal Glx and CSF p-tau181 in APOE4 carriers (Pearson's r = 0.76, p = 0.02), but not after adjusting for covariates. In the entire cohort, there was a direct correlation between hippocampal NAA and hippocampal volume (Spearman's r = 0.55, p = 0.001), even after adjusting for age and Fazekas score (Spearman's r = 0.48, p = 0.006). This relationship was observed only in APOE4 carriers (Pearson's r = 0.66, p = 0.017), and was also retained after adjustment (Pearson's r = 0.76, p = 0.008; metabolite-by-carrier interaction p = 0.03). There were no findings in the PCC, nor in the negative control (late Braak stage) regions of the precuneus and precentral gyrus. CONCLUSIONS: Our findings are in line with the spatially- and temporally-resolved Braak staging model of pathological severity in which the hippocampus is affected earlier than the PCC. The correlations, between MRS markers of synaptic and neuronal health and, respectively, T and N pathology, were found exclusively within APOE4 carriers, suggesting a connection with AD pathological change, rather than with normal aging. We therefore conclude that MRS has the potential to augment early A/T/N staging, with the hippocampus serving as a more sensitive MRS target compared to the PCC.

A Comprehensive Study of Factors Affecting the Prediction of the pKa Shift of Asp26 in Thioredoxin Protein.

The stable protonation state of ionizable amino acids in a protein can be predicted by computing the pKa shift of that residue within the protein environment. Thermodynamic Integration (TI) is an ideal molecular dynamics-based approach for predicting the pKa shift of ionizable protein residues. Here, we probe TI-based simulation protocols for their ability to accurately predict the pKa shift of Asp26 in thioredoxin. While implicit solvent models can predict the pKa shift accurately, explicit solvent models result in substantial errors. To understand the underlying reason for this surprising discrepancy, we investigate the role of various factors such as solvent models, conformational sampling, background charges, and polarization.

Characterization of different-sized human αA-crystallin homomers and implications to Asp151 isomerization.

Site-specific modifications of aspartate residues spontaneously occur in crystallin, the major protein in the lens. One of the primary modification sites is Asp151 in αA-crystallin. Isomerization and racemization alter the crystallin backbone structure, reducing its stability by inducing abnormal crystallin-crystallin interactions and ultimately leading to the insolubilization of crystallin complexes. These changes are considered significant factors in the formation of senile cataracts. However, the mechanisms driving spontaneous isomerization and racemization have not been experimentally demonstrated. In this study, we generated αA-crystallins with different homo-oligomeric sizes and/or containing an asparagine residue at position 151, which is more prone to isomerization and racemization. We characterized their structure, hydrophobicity, chaperone-like function, and heat stability, and examined their propensity for isomerization and racemization. The results show that the two differently sized αA-crystallin variants possessed similar secondary structures but exhibited different chaperone-like functions depending on their oligomeric sizes. The rate of isomerization and racemization of Asp151, as assessed by the deamidation of Asn151, was also found to depend on the oligomeric sizes of αA-crystallin. The predominant isomerization product via deamidation of Asn151 in the different-sized αA-crystallin variants was L-ß-Asp in vitro, while various modifications occurred around Asp151 in vivo. The disparity between the findings of this in vitro study and in vivo studies suggests that the isomerization of Asp151 in vivo may be more complex than what occurs in vitro.

Predicting performance in attention by measuring key metabolites in the PCC with 7T MRS.

The posterior cingulate cortex (PCC) is a key hub of the default mode network and is known to play an important role in attention. Using ultra-high field 7 Tesla magnetic resonance spectroscopy (MRS) to quantify neurometabolite concentrations, this exploratory study investigated the effect of the concentrations of myo-inositol (Myo-Ins), glutamate (Glu), glutamine (Gln), aspartate or aspartic acid (Asp) and gamma-amino-butyric acid (GABA) in the PCC on attention in forty-six healthy participants. Each participant underwent an MRS scan and cognitive testing, consisting of a trail-making test (TMT A/B) and a test of attentional performance. After a multiple regression analysis and bootstrapping for correction, the findings show that Myo-Ins and Asp significantly influence (p < 0.05) attentional tasks. On one hand, Myo-Ins shows it can improve the completion times of both TMT A and TMT B. On the other hand, an increase in aspartate leads to more mistakes in Go/No-go tasks and shows a trend towards enhancing reaction time in Go/No-go tasks and stability of alertness without signal. No significant (p > 0.05) influence of Glu, Gln and GABA was observed.

Novel DNA-Binding Activity Exhibited by Poly(aspartic acid) Hydrolase-1 Inhibits Poly(aspartic acid) Hydrolase Activity.

Significant attention has been shifted toward the use and development of biodegradable polymeric materials to mitigate environmental accumulation and potential health impacts. One such material, poly(aspartic acid) (PAA), is a biodegradable alternative to superabsorbent poly(carboxylates), like poly(acrylate). Three enzymes are known to hydrolyze PAA: PahZ1KT-1 and PahZ2KT-1 from Sphingomonas sp. KT-1 and PahZ1KP-2 from Pedobacter sp. KP-2. We previously reported the X-ray crystal structure for PahZ1KT-1, which revealed a homodimer complex with a strongly cationic surface spanning one side of each monomer. Here, we report the first characterization of any polymer hydrolase binding to DNA, where modeling data predict binding of the polyanionic DNA near the cationic substrate binding surface. Our data reveal that PahZ1 homologues from Sphingomonas sp. KT-1 and Pedobacter sp. KP-2 bind ssDNA and dsDNA with nanomolar binding affinities. PahZ1KT-1 binds ssDNA and dsDNA with an apparent dissociation constant, KD,app = 81 ± 14 and 19 ± 1 nM, respectively, and these estimates are similar to the same behaviors exhibited by PahZ1KP-2. Gel permeation chromatography data reveal that dsDNA binding promotes inhibition of PahZ1-catalyzed PAA biodegradation for each homologue. We propose a working model wherein binding of PahZ1 to extracellular biofilm DNA aids in the localization of the hydrolase to the environment in which PAA would first be encountered, thereby providing a mechanism to degrade extracellular PAA and potentially harvest aspartic acid for nutritional uptake.

Association of Cortical Lesions With Regional Glutamate, GABA, N-Acetylaspartate, and Myoinositol Levels in Patients With Multiple Sclerosis.

BACKGROUND AND OBJECTIVES: Cortical lesions contribute to disability in multiple sclerosis (MS), but their impact on regional neurotransmitter levels remains to be clarified. We tested the hypothesis that cortical lesions are associated with regional glutamate and gamma-aminobutyric acid (GABA) concentrations within the affected cortical region. METHODS: In this cross-sectional study, we used structural 7T MRI to segment cortical lesions and 7T proton MR-spectroscopy of the bilateral sensorimotor hand areas to quantify regional GABA, glutamate, N-acetylaspartate, and myoinositol concentrations in patients with MS (inclusion criteria: diagnosis of relapsing-remitting [RR] or secondary progressive MS [SPMS]; age 18-80 years) and age and sex-matched healthy controls. Data were collected at a single center between August 2018 and September 2020. Linear mixed-effects models were used to test for associations between metabolite concentrations and cortical lesion volumes within the same MR-spectroscopy voxel. RESULTS: Forty-seven patients with MS (34 RRMS, 13 SPMS; 45.1 ± 12.5 years; 31 women) and 23 healthy controls (44.4 ± 13 years, 15 women) were studied. In patients, higher regional glutamate and lower regional GABA concentrations were associated with larger cortical lesion volume within the MR-spectroscopy voxel [glutamate: 0.61 (95% CI 0.19-1.03) log(mm3), p = 0.005, GABA: -0.71 (-1.24 to -0.18) log(mm3), p = 0.01]. In addition, lower N-acetylaspartate levels [-0.37 (-0.67 to -0.07) log(mm3), p = 0.016] and higher myoinositol levels [0.48 (0.03-0.93) log(mm3), p = 0.037] were associated with a larger regional cortical lesion volume. Furthermore, glutamate concentrations were reduced in patients with SPMS compared with healthy participants [-0.75 (-1.3 to -0.19) mM, p = 0.005] and patients with RRMS [-0.55 (-1.07 to -0.02) mM, p = 0.04]. N-acetylaspartate levels were lower in both patients with RRMS [-0.81 (-1.39 to -0.24) mM, p = 0.003] and SPMS [-1.31 (-2.07 to -0.54) mM, p < 0.001] when compared with healthy controls. Creatine-normalized N-acetylaspartate levels were associated with performance in the 9-hole peg test of the contralateral hand [-0.004 (-0.007 to -0.002) log(s), p = 0.002], and reduced mean creatine-normalized glutamate was associated with increased Expanded Disability Status Scale (R = -0.39, p = 0.02). DISCUSSION: Cortical lesions are associated with local increases in glutamate and a reduction in GABA concentration within the lesional or perilesional tissue. Further studies are needed to investigate the causal relationship between cortical lesions and changes in neurotransmitter concentrations.

Inborn errors of the malate aspartate shuttle - Update on patients and cellular models.

The malate aspartate shuttle (MAS) plays a pivotal role in transporting cytosolic reducing equivalents - electrons - into the mitochondria for energy conversion at the electron transport chain (ETC) and in the process of oxidative phosphorylation. The MAS consists of two pairs of cytosolic and mitochondrial isoenzymes (malate dehydrogenases 1 and 2; and glutamate oxaloacetate transaminases 1 and 2) and two transporters (malate-2-oxoglutarate carrier and aspartate glutamate carrier (AGC), the latter of which has two tissue-dependent isoforms AGC1 and AGC2). While the inner mitochondrial membrane is impermeable to NADH, the MAS forms one of the main routes for mitochondrial electron uptake by promoting uptake of malate. Inherited bi-allelic pathogenic variants in five of the seven components of the MAS have been described hitherto and cause a wide spectrum of symptoms including early-onset epileptic encephalopathy. This review provides an overview of reported patients suffering from MAS deficiencies. In addition, we give an overview of diagnostic procedures and research performed on patient-derived cellular models and tissues. Current cellular models are briefly discussed and novel ways to achieve a better understanding of MAS deficiencies are highlighted.

Unexpected weakened formation of disinfection byproducts and enhanced production of halates by cupric oxide during chlorination of peptide-bound aspartic acid.

Under the condition that the residual chlorine is guaranteed, the biofilm still thrives in drinking water distribution systems through secreting a large number of extracellular polymeric substances (EPS), in which protein components are the primary precursor of disinfection byproducts (DBPs), mostly in the form of combined amino acids. The aim of this study is to investigate the action of CuO on the formation of halates (XO3-, ClO3- and BrO3-) and DBPs (trihalomethanes, THMs; haloacetonitriles, HANs) with aspartic acid tetrapeptide (TAsp) as protein surrogate. The presence of CuO promoted the self-decay rather than TAsp-induced decay of oxidants, resulting in an increase in XO3- yield and a decrease in DBPs yield. It was CuO-induced weaker production of cyanoacetic acid and 3-oxopropanoic acid that induced the decreased yields of HANs and THMs, respectively. The FTIR and Raman spectra indicate a weak complexation between CuO and TAsp. Given this, the CuO-HOX/OX- complexes were inferred to be reactive to HOX/OX- but less reactive to TAsp. The study helps to better understand the formation of XO3- and DBPs during the chlorination of EPS, and propose precise control strategies when biofilm boosts in water pipes.

Region-specific Cerebral Metabolic Alterations in Parkinson's Disease Patients With/without Mild Cognitive Impairment.

N-acetylaspartate (NAA), choline (Cho) and creatine (Cr) are brain metabolites involved in some key neuronal functions within the brain, such as cognitive function. The aim of this study was to investigate whether Parkinson's disease (PD) with different cognitive status induces regional brain metabolite differences. 38 diagnosed PD patients, including 18 PD patients with normal cognitive (PDN), 20 PD subjects with cognitive impairment (PDMCI) and 25 healthy controls (HC) participated in this study. All subjects underwent a single-voxel proton MR spectroscopy (1H-MRS) on a 3T scanner. 1H-MRS were obtained from bilateral PCC, left thalamus and PFC regions in all subjects, respectively. Region-specific cerebral metabolic alterations existed in PD patients with different cognitive status. PDMCI patients showed a significant reduction of NAA, Cho and tCr in the PCC and left thalamus, compared to healthy controls; whereas lower levels of NAA and Cho in thalamus were found in PDN patients. Moreover, Cho and tCr levels were positively correlated with MMSE scores. Both NAA and tCr in PCC levels were positively correlated with MMSE and MoCA scores. The combination of thalamic and PCC metabolites showed a 75.6% accuracy in distinguishing PDMCI patients from PDN patients. This study provides preliminary evidence that thalamic, PCC and PFC neurometabolic alterations occur in PD patients with cognition decline. Findings of this study indicate that NAA and tCr abnormalities in PCC and thalamus might be used as a biomarker to track cognitive decline in Parkinson's disease in clinical settings.

Neurochemical changes in the progression of Huntington's disease: A meta-analysis of in vivo1H-MRS studies.

Proton magnetic resonance spectroscopy (1H-MRS) allows measuring specific brain metabolic alterations in Huntington's disease (HD), and these metabolite profiles may serve as non-invasive biomarkers associated with disease progression. Despite this potential, previous findings are inconsistent. Accordingly, we performed a meta-analysis on available in vivo1H-MRS studies in premanifest (Pre-HD) and symptomatic HD stages (Symp-HD), and quantified neurometabolic changes relative to controls in 9 Pre-HD studies (227 controls and 188 mutation carriers) and 14 Symp-HD studies (326 controls and 306 patients). Our results indicated decreased N-acetylaspartate and creatine in the basal ganglia in both Pre-HD and Symp-HD. The overall level of myo-inositol was decreased in Pre-HD while increased in Symp-HD. Besides, Symp-HD patients showed more severe metabolism disruption than Pre-HD patients. Taken together, 1H-MRS is important for elucidating progressive metabolite changes from Pre-HD to clinical conversion; N-acetylaspartate and creatine in the basal ganglia are already sensitive at the preclinical stage and are promising biomarkers for tracking disease progression; overall myo-inositol is a possible characteristic metabolite for distinguishing HD stages.

Preserving ester-linked modifications reveals glutamate and aspartate mono-ADP-ribosylation by PARP1 and its reversal by PARG.

Ester-linked post-translational modifications, including serine and threonine ubiquitination, have gained recognition as important cellular signals. However, their detection remains a significant challenge due to the chemical lability of the ester bond. This is the case even for long-known modifications, such as ADP-ribosylation on aspartate and glutamate, whose role in PARP1 signaling has recently been questioned. Here, we present easily implementable methods for preserving ester-linked modifications. When combined with a specific and sensitive modular antibody and mass spectrometry, these approaches reveal DNA damage-induced aspartate/glutamate mono-ADP-ribosylation. This previously elusive signal represents an initial wave of PARP1 signaling, contrasting with the more enduring nature of serine mono-ADP-ribosylation. Unexpectedly, we show that the poly-ADP-ribose hydrolase PARG is capable of reversing ester-linked mono-ADP-ribosylation in cells. Our methodology enables broad investigations of various ADP-ribosylation writers and, as illustrated here for noncanonical ubiquitination, it paves the way for exploring other emerging ester-linked modifications.

Bioinformatics leading to conveniently accessible, helix enforcing, bicyclic ASX motif mimics (BAMMs).

Helix mimicry provides probes to perturb protein-protein interactions (PPIs). Helical conformations can be stabilized by joining side chains of non-terminal residues (stapling) or via capping fragments. Nature exclusively uses capping, but synthetic helical mimics are heavily biased towards stapling. This study comprises: (i) creation of a searchable database of unique helical N-caps (ASX motifs, a protein structural motif with two intramolecular hydrogen-bonds between aspartic acid/asparagine and following residues); (ii) testing trends observed in this database using linear peptides comprising only canonical L-amino acids; and, (iii) novel synthetic N-caps for helical interface mimicry. Here we show many natural ASX motifs comprise hydrophobic triangles, validate their effect in linear peptides, and further develop a biomimetic of them, Bicyclic ASX Motif Mimics (BAMMs). BAMMs are powerful helix inducing motifs. They are synthetically accessible, and potentially useful to a broad section of the community studying disruption of PPIs using secondary structure mimics.

Targeting c-Myc transactivation by LMNA inhibits tRNA processing essential for malate-aspartate shuttle and tumour progression.

BACKGROUND: A series of studies have demonstrated the emerging involvement of transfer RNA (tRNA) processing during the progression of tumours. Nevertheless, the roles and regulating mechanisms of tRNA processing genes in neuroblastoma (NB), the prevalent malignant tumour outside the brain in children, are yet unknown. METHODS: Analysis of multi-omics results was conducted to identify crucial regulators of downstream tRNA processing genes. Co-immunoprecipitation and mass spectrometry methods were utilised to measure interaction between proteins. The impact of transcriptional regulators on expression of downstream genes was measured by dual-luciferase reporter, chromatin immunoprecipitation, western blotting and real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) methods. Studies have been conducted to reveal impact and mechanisms of transcriptional regulators on biological processes of NB. Survival differences were analysed using the log-rank test. RESULTS: c-Myc was identified as a transcription factor driving tRNA processing gene expression and subsequent malate-aspartate shuttle (MAS) in NB cells. Mechanistically, c-Myc directly promoted the expression of glutamyl-prolyl-tRNA synthetase (EPRS) and leucyl-tRNA synthetase (LARS), resulting in translational up-regulation of glutamic-oxaloacetic transaminase 1 (GOT1) as well as malate dehydrogenase 1 (MDH1) via inhibiting general control nonrepressed 2 or activating mechanistic target of rapamycin signalling. Meanwhile, lamin A (LMNA) inhibited c-Myc transactivation via physical interaction, leading to suppression of MAS, aerobic glycolysis, tumourigenesis and aggressiveness. Pre-clinically, lobeline was discovered as a LMNA-binding compound to facilitate its interaction with c-Myc, which inhibited aminoacyl-tRNA synthetase expression, MAS and tumour progression of NB, as well as growth of organoid derived from c-Myc knock-in mice. Low levels of LMNA or elevated expression of c-Myc, EPRS, LARS, GOT1 or MDH1 were linked to a worse outcome and a shorter survival time of clinical NB patients. CONCLUSIONS: These results suggest that targeting c-Myc transactivation by LMNA inhibits tRNA processing essential for MAS and tumour progression.