Large-scale separation of alkaloids from Corydalis decumbens by pH-zone-refining centrifugal partition chromatography and their anticomplement activity.

Centrifugal partition chromatography in the pH-zone-refining mode was successfully applied to the separation of alkaloids from the crude extract of Corydalis decumbens. The experiment was performed with a two-phase solvent system composed of petroleum ether-ethyl acetate-ethanol-water (5:5:3:7, v/v/v/v) where triethylamine (10 mM) was added to the stationary phase and hydrochloric acid (10 mM) to the mobile phase. From 1.6 g of the crude extract, 43 mg protopine, 189 mg (+)-egenine, and 158 mg tetrahydropalmatine were obtained with a purity of 98.2%, 94.6%, and 96.7%, respectively. Tetrahydropalmatine showed an interesting anticomplement effect with CH50 0.11 and AP50 0.25 mg/mL, respectively. In a mechanistic study, tetrahydropalmatine interacted with C1, C3, C4, and C5 components in the complement activation cascade.

Spermine promotes pulmonary vascular remodelling and its synthase is a therapeutic target for pulmonary arterial hypertension.

Pathological mechanisms of pulmonary arterial hypertension (PAH) remain largely unexplored. Effective treatment of PAH remains a challenge. The aim of this study was to discover the underlying mechanism of PAH through functional metabolomics and to help develop new strategies for prevention and treatment of PAH.Metabolomic profiling of plasma in patients with idiopathic PAH was evaluated through high-performance liquid chromatography mass spectrometry, with spermine identified to be the most significant and validated in another independent cohort. The roles of spermine and spermine synthase were examined in pulmonary arterial smooth muscle cells (PASMCs) and rodent models of pulmonary hypertension.Using targeted metabolomics, plasma spermine levels were found to be higher in patients with idiopathic PAH compared to healthy controls. Spermine administration promoted proliferation and migration of PASMCs and exacerbated vascular remodelling in rodent models of pulmonary hypertension. The spermine-mediated deteriorative effect can be attributed to a corresponding upregulation of its synthase in the pathological process. Inhibition of spermine synthase in vitro suppressed platelet-derived growth factor-BB-mediated proliferation of PASMCs, and in vivo attenuated monocrotaline-mediated pulmonary hypertension in rats.Plasma spermine promotes pulmonary vascular remodelling. Inhibiting spermine synthesis could be a therapeutic strategy for PAH.

Germline BMP9 mutation causes idiopathic pulmonary arterial hypertension.

BACKGROUND: Idiopathic pulmonary arterial hypertension (IPAH) is a rare disease with high heritability. Although several predisposing genes have been linked to IPAH, the genetic aetiology remains unknown for a large number of IPAH cases. METHODS: We conducted an exome-wide gene-based burden analysis on two independent case-control studies, including a total of 331 IPAH cases and 10 508 controls. Functional assessments were conducted to analyse the effects of genetic mutations on protein biosynthesis and function. RESULTS: The gene encoding human bone morphogenetic protein 9 (BMP9) was identified as a novel genetic locus displaying exome-wide association with IPAH in the discovery cohort (OR 18.8; p=1.9×10-11). This association was authenticated in the independent replication cohort (p=1.0×10-5). Collectively, the rare coding mutations in BMP9 occurred in 6.7% of cases, ranking this gene second to BMPR2, comprising a combined significance of 2.7×10-19 (OR 21.2). Intriguingly, the patients with BMP9 mutations had lower plasma levels of BMP9 than those without. Functional studies showed that the BMP9 mutations led to reduced BMP9 secretion and impaired anti-apoptosis ability in pulmonary arterial endothelial cells. CONCLUSION: We identify BMP9 as an IPAH culprit gene.

Low power consumption thermo-optic switch formed by an integrated processing method.

In this paper, an integrated processing method was demonstrated to fabricate the polymer-based thermo-optic (TO) switch with low power consumption. The characteristic parameters of the switch were carefully designed and simulated. The air trench structure was exploited to reduce the power consumption, which can be formed with the waveguide simultaneously by the integrated processing method. Moreover, the introduced polymer/silica hybrid waveguide structure can also improve the response time of the device. A typical fabricated switch presented a low switching power of 5.2 mW. The measured switching rise time and fall time are 192.2 and 201.1 µs, respectively.

Metabolic reprogramming of the urea cycle pathway in experimental pulmonary arterial hypertension rats induced by monocrotaline.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a rare systemic disorder associated with considerable metabolic dysfunction. Although enormous metabolomic studies on PAH have been emerging, research remains lacking on metabolic reprogramming in experimental PAH models. We aim to evaluate the metabolic changes in PAH and provide new insight into endogenous metabolic disorders of PAH. METHOD: A single subcutaneous injection of monocrotaline (MCT) (60 mg kg- 1) was used for rats to establish PAH model. Hemodynamics and right ventricular hypertrophy were adopted to evaluate the successful establishment of PAH model. Plasma samples were assessed through targeted metabolomic profiling platform to quantify 126 endogenous metabolites. Orthogonal partial least squares discriminant analysis (OPLS-DA) was used to discriminate between MCT-treated model and control groups. Metabolite Set Enrichment Analysis was adapted to exploit the most disturbed metabolic pathways. RESULTS: Endogenous metabolites of MCT treated PAH model and control group were well profiled using this platform. A total of 13 plasma metabolites were significantly altered between the two groups. Metabolite Set Enrichment Analysis highlighted that a disruption in the urea cycle pathway may contribute to PAH onset. Moreover, five novel potential biomarkers in the urea cycle, adenosine monophosphate, urea, 4-hydroxy-proline, ornithine, N-acetylornithine, and two candidate biomarkers, namely, O-acetylcarnitine and betaine, were found to be highly correlated with PAH. CONCLUSION: The present study suggests a new role of urea cycle disruption in the pathogenesis of PAH. We also found five urea cycle related biomarkers and another two candidate biomarkers to facilitate early diagnosis of PAH in metabolomic profile.

Functions and novel regulatory mechanisms of key glycolytic enzymes in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a progressive vascular disease characterized by remodeling of the pulmonary vasculature and elevated pulmonary arterial pressure, ultimately leading to right heart failure and death. Despite its clinical significance, the precise molecular mechanisms driving PAH pathogenesis warrant confirmation. Compelling evidence indicates that during the development of PAH, pulmonary vascular cells exhibit a preference for energy generation through aerobic glycolysis, known as the "Warburg effect", even in well-oxygenated conditions. This metabolic shift results in imbalanced metabolism, increased proliferation, and severe pulmonary vascular remodeling. Exploring the Warburg effect and its interplay with glycolytic enzymes in the context of PAH has yielded current insights into emerging drug candidates targeting enzymes and intermediates involved in glucose metabolism. This sheds light on both opportunities and challenges in the realm of antiglycolytic therapy for PAH.

Prognostic Value of Plasma Immunoglobulin G N-Glycome Traits in Pulmonary Arterial Hypertension.

BACKGROUND: B-type natriuretic peptide or N-terminal pro-B-type natriuretic peptide is the only blood biomarker in established risk calculators for pulmonary arterial hypertension (PAH). Profiling systemic-originated plasma immunoglobulin G (IgG) N-glycans, which reflect different components of the pathophysiology of PAH including immune dysregulation and inflammation, may improve PAH risk assessment. OBJECTIVES: This study sought to identify plasma IgG N-glycan biomarkers that predict survival in PAH to improve risk assessment. METHODS: This cohort study examined 622 PAH patients from 2 national centers (Beijing [discovery] cohort: n = 273; Shanghai [validation] cohort: n = 349). Plasma IgG N-glycomes were profiled by a robust mass spectrometry-based method. Prognostic IgG N-glycan traits were identified and validated in the 2 cohorts using Cox regression and Kaplan-Meier survival analyses. The added value of IgG N-glycan traits to previously established risk models was assessed using Harrell C-indexes and survival analysis. RESULTS: Plasma IgG fucosylation was found to predict survival independent of age and sex in the discovery cohort (HR: 0.377; 95% CI: 0.168-0.845; P = 0.018) with confirmation in the validation cohort (HR: 0.445; 95% CI: 0.264-0.751; P = 0.005). IgG fucosylation remained a robust predictor of mortality in combined cohorts after full adjustment and in subgroup analyses. Integrating IgG fucosylation into previously established risk models improved their predictive capacity, marked by an overall elevation in Harrell C-indexes. IgG fucosylation was useful in further stratifying the intermediate-risk patients classified by a previously established model. CONCLUSIONS: Plasma IgG fucosylation informs PAH prognosis independent of established factors, offering additional value for predicting PAH outcomes.

Clonal Hematopoiesis of Indeterminate Potential in Chronic Thromboembolic Pulmonary Hypertension: A Multicenter Study.

BACKGROUND: The pathogenesis of chronic thromboembolic pulmonary hypertension (CTEPH) is multifactorial and growing evidence has indicated that hematological disorders are involved. Clonal hematopoiesis of indeterminate potential (CHIP) has recently been associated with an increased risk of both hematological malignancies and cardiovascular diseases. However, the prevalence and clinical relevance of CHIP in patients with CTEPH remains unclear. METHODS: Using stepwise calling on next-generation sequencing data from 499 patients with CTEPH referred to 3 centers between October 2006 and December 2021, CHIP mutations were identified. We associated CHIP with all-cause mortality in patients with CTEPH. To provide insights into potential mechanisms, the associations between CHIP and inflammatory markers were also determined. RESULTS: In total, 47 (9.4%) patients with CTEPH carried at least 1 CHIP mutation at a variant allele frequency of ≥2%. The most common mutations were in DNMT3A, TET2, RUNX1, and ASXL1. During follow-up (mean, 55 months), deaths occurred in 22 (46.8%) and 104 (23.0%) patients in the CHIP and non-CHIP groups, respectively (P<0.001, log-rank test). The association of CHIP with mortality remained robust in the fully adjusted model (hazard ratio, 2.190 [95% CI, 1.257-3.816]; P=0.006). Moreover, patients with CHIP mutations showed higher circulating interleukin-1ß and interleukin-6 and lower interleukin-4 and IgG galactosylation levels. CONCLUSIONS: This is the first study to show that CHIP mutations occurred in 9.4% of patients with CTEPH are associated with a severe inflammatory state and confer a poorer prognosis in long-term follow-up.

Congenital thrombophilia in East-Asian venous thromboembolism population: a systematic review and meta-analysis.

Background: Various inherited traits contribute to the overall risk of venous thromboembolism (VTE). In addition, the epidemiology of thrombophilia in the East-Asian VTE population remains unclear; thus, we aimed to assess the proportion of hereditary thrombophilia via a meta-analysis. Methods: Publications from PubMed, EMBASE, web of science, and Cochrane before December 30, 2022, were searched. Studies from Japan, Korea, China, Hong Kong, Taiwan, Singapore, Thailand, Vietnam, Myanmar, and Cambodia were included. Congenital thrombophilia was described as diseases including protein C (PC) deficiency, protein S (PS) deficiency, antithrombin (AT) deficiency, factor (F)V Leiden (FVL), and prothrombin G20210A mutations. Studies were selected by 2 reviewers for methodological quality analysis. A random-effects model was used for the meta-analysis, assuming that estimated effects in the different studies are not identical. Results: Forty-four studies involving 6453 patients from 7 counties/regions were included in the meta-analysis. The prevalence of PC, PS, and AT deficiencies were 7.1%, 8.3%, and 3.8%, respectively. Among 2924 patients from 22 studies, 5 patients were carriers of FVL mutation. Among 2196 patients from 10 studies, 2 patients were carriers of prothrombin G20210A mutation in a Thailand study. Conclusion: The prevalence of PC, PS, and AT deficiencies was relatively high, while a much lower prevalence of FVL and prothrombin G20210A mutations were identified in East-Asian patients with VTE. Our data stress the relative higher prevalence of PC, PS, and AT deficiencies for thrombophilia in the East-Asian VTE population.

MicroRNAs and their regulators: Potential therapeutic targets in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a complex and progressive disease characterized by pulmonary arterial remodeling. Despite that current combination therapy has shown improvement in morbidity and mortality, a better deciphering of the underlying pathological mechanisms and novel therapeutic targets is urgently needed to combat PAH. MicroRNA, the critical element in post-transcription mechanisms, mediates cellular functions mainly by tuning downstream target gene expression. Meanwhile, upstream regulators can regulate miRNAs in synthesis, transcription, and function. In vivo and in vitro studies have suggested that miRNAs and their regulators are involved in PAH. However, the miRNA-related regulatory mechanisms governing pulmonary vascular remodeling and right ventricular dysfunction remain elusive. Hence, this review summarized the controversial roles of miRNAs in PAH pathogenesis, focused on different miRNA-upstream regulators, including transcription factors, regulatory networks, and environmental stimuli, and finally proposed the prospects and challenges for the therapeutic application of miRNAs and their regulators in PAH treatment.

Human Plasma IgG N-Glycome Profiles Reveal a Proinflammatory Phenotype in Chronic Thromboembolic Pulmonary Hypertension.

BACKGROUND: The pathological mechanism of chronic thromboembolic pulmonary hypertension (CTEPH) is not fully understood, and inflammation has been reported to be one of its etiological factors. IgG regulates systemic inflammatory homeostasis, primarily through its N-glycans. Little is known about IgG N-glycosylation in CTEPH. We aimed to map the IgG N-glycome of CTEPH to provide new insights into its pathogenesis and discover novel markers and therapies. METHODS: We characterized the plasma IgG N-glycome of patients with CTEPH in a discovery cohort and validated our results in an independent validation cohort using matrix-assisted laser desorption/ionization time of flight mass spectrometry. Thereafter, we correlated IgG N-glycans with clinical parameters and circulating inflammatory cytokines in patients with CTEPH. Furthermore, we determined IgG N-glycan quantitative trait loci in CTEPH to reveal partial mechanisms underlying glycan changes. RESULTS: Decreased IgG galactosylation representing a proinflammatory phenotype was found in CTEPH. The distribution of IgG galactosylation showed a strong association with NT-proBNP (N-terminal pro-B-type natriuretic peptide) in CTEPH. In line with the glycomic findings, IgG pro-/anti-inflammatory N-glycans correlated well with a series of inflammatory markers and gene loci that have been reported to be involved in the regulation of these glycans or inflammatory immune responses. CONCLUSIONS: This is the first study to reveal the full signature of the IgG N-glycome of a proinflammatory phenotype and the genes involved in its regulation in CTEPH. Plasma IgG galactosylation may be useful for evaluating the inflammatory state in patients with CTEPH; however, this requires further validation. This study improves our understanding of the mechanisms underlying CTEPH inflammation from the perspective of glycomics.

Optimization and structure-activity relationships of a series of potent inhibitors of methicillin-resistant Staphylococcus aureus (MRSA) pyruvate kinase as novel antimicrobial agents.

A novel series of hydrazones were synthesized and evaluated as inhibitors of methicillin-resistant Staphylococcus aureus (MRSA) pyruvate kinase (PK). PK has been identified as one of the most highly connected 'hub proteins' in MRSA. PK has been shown to be critical for bacterial survival which makes it a potential target for development of novel antibiotics and the high degree of connectivity implies it should be very sensitive to mutations and thus less able to develop resistance. PK is not unique to bacteria and thus a critical requirement for such a PK inhibitor would be that it does not inhibit the homologous human enzyme(s) at therapeutic concentrations. Several MRSA PK inhibitors (including 8d) were identified using in silico screening combined with enzyme assays and were found to be selective for bacterial enzyme compared to four human PK isoforms (M1, M2, R and L). However these lead compounds did not show significant inhibitory activity for MRSA growth presumably due to poor bacterial cell penetration. Structure-activity relationship (SAR) studies were carried out on 8d and led us to discover more potent compounds with enzyme inhibiting activities in the low nanomolar range and some were found to effectively inhibit bacteria growth in culture with minimum inhibitory concentrations (MIC) as low as 1 µg/mL. These inhibitors bind in two elongated flat clefts found at the minor interfaces in the homo-tetrameric enzyme complex and the observed SAR is in keeping with the size and electronic constraints of these binding sites. Access to the corresponding sites in the human enzyme is blocked.

Boosting Highly Active Exposed Mo Atoms by Fine-Tuning S-Vacancies of MoS2-Based Materials for Efficient Hydrogen Evolution.

Guided by the theoretical calculation, achieving an efficient hydrogen evolution reaction (HER) by S-vacancy engineering toward MoS2-based materials is quite challenging due to the contradictory relationship between the adsorption free energy of hydrogen atoms (ΔGH) of the exposed Mo atoms (EMAs) and the number of EMAs per unit area (NEMAs). Herein, we demonstrate a novel one-pot incorporating-assisted compositing strategy to realize fine-tuning the concentration of S-vacancies (CS-vacancies) of MoS2-based materials to boost highly active EMAs for efficient HER. In our strategy, S-vacancies are modulated into basal planes of MoS2 via decreasing the formation energy of S-vacancies by oxygen incorporation; moreover, CS-vacancies of the basal planes is precisely regulated by simply controlling the molar amount of the Co precursor based on the electron injection effect. At low or excessively high CS-vacancies, the as-synthesized electrocatalysts lack "highly active EMAs" in quantity or nature. The balance between the intrinsic activity of EMAs and NEMAs is realized for boosting EMAs with high catalytic performance. The optimal electrocatalysts exhibit excellent activity and stability at fine-tuning CS-vacancies to 9.61%. Our results will pave a novel strategy for unlocking the potential of an inert basal plane in MoS2 for high-performance HER.

Synergistic Regulation of S-Vacancy of MoS2-Based Materials for Highly Efficient Electrocatalytic Hydrogen Evolution.

Low or excessively high concentration of S-vacancy (C S-vacancy) is disadvantageous for the hydrogen evolution reaction (HER) activity of MoS2-based materials. Additionally, alkaline water electrolysis is most likely to be utilized in the industry. Consequently, it is of great importance for fine-tuning C S-vacancy to significantly improve alkaline hydrogen evolution. Herein, we have developed a one-step Ru doping coupled to compositing with CoS2 strategy to precisely regulate C S-vacancy of MoS2-based materials for highly efficient HER. In our strategy, Ru doping favors the heterogeneous nucleation and growth of CoS2, which leads to a high crystallinity of Ru-doped CoS2 (Ru-CoS2) and rich heterogeneous interfaces between Ru-CoS2 and Ru-doped MoS2-x (Ru-MoS2-x). This facilitates the electron transfer from Ru-CoS2 to Ru-MoS2-x, thereby increasing C S-vacancy of MoS2-based materials. Additionally, the electron injection effect increases gradually with an increase in the mass of Co precursor (m Co), which implies more S2- leaching from MoS2 at higher m Co. Subsequently, C S-vacancy of the as-synthesized samples is precisely regulated by the synergistic engineering of Ru doping and compositing with CoS2. At C S-vacancy = 17.1%, a balance between the intrinsic activity and the number of exposed Mo atoms (EMAs) to boost highly active EMAs should be realized. Therefore, the typical samples demonstrate excellent alkaline HER activity, such as a low overpotential of 170 mV at 100 mA cm-2 and a TOF of 4.29 s-1 at -0.2 V. Our results show promise for important applications in the fields of electrocatalysis or energy conversion.

Prevalence, Genetic Background, and Clinical Phenotype of Congenital Thrombophilia in Chronic Thromboembolic Pulmonary Hypertension.

Background: The role of congenital thrombophilia in chronic thromboembolic pulmonary hypertension (CTEPH) remains unresolved. Objectives: The purpose of this study was to investigate the prevalence, genetic background, and clinical phenotype of congenital thrombophilia in CTEPH. Methods: In total, 367 patients with CTEPH from May 2013 to December 2020 were consecutively enrolled in this cross-sectional study in FuWai Hospital and Peking Union Medical College Hospital in China. The primary outcome was the occurrence of congenital thrombophilia diagnosed through tests for congenital anticoagulants activity (including protein C, protein S, and antithrombin III), factor V Leiden and prothrombin G20210A sequence variants. Next-generation sequencing was conducted for patients with congenital thrombophilia. Clinical phenotype was compared between patients with and without thrombophilia. Results: A total of 36 (9.8%; 95% CI: 6.8%-12.9%) patients were diagnosed as congenital thrombophilia, including 13 protein C deficiency (3.5%; 95% CI: 1.6%-5.4%), 19 protein S deficiency (5.2%; 95% CI: 2.9%-7.5%), and 4 antithrombin III deficiency (1.1%; 95% CI: 0%-2.2%). No factor V Leiden or prothrombin G20210A sequence variants were identified. Genotype for patients with thrombophilia revealed that 10 (76.9%) protein C deficiency patients were PROC sequence variant carriers, 4 (21.1%) protein S deficiency were PROS1 sequence variant carriers, and 2 (50.0%) antithrombin III deficiency were SERPINC1 sequence variant carriers. In the logistic regression model, male sex (OR: 3.24; 95% CI: 1.43-7.31) and proximal lesion in pulmonary arteries (OR: 4.10; 95% CI: 1.91-8.85) had significant differences between the congenital thrombophilia and nonthrombophilia group in CTEPH patients. Conclusions: Congenital thrombophilia was not rare. Male sex and proximal lesion in pulmonary arteries might be the specific clinical phenotype for CTEPH patients with congenital thrombophilia.

Mapping the protein interaction network in methicillin-resistant Staphylococcus aureus.

Mortality attributable to infection with methicillin-resistant Staphylococcus aureus (MRSA) has now overtaken the death rate for AIDS in the United States, and advances in research are urgently needed to address this challenge. We report the results of the systematic identification of protein-protein interactions for the hospital-acquired strain MRSA-252. Using a high-throughput pull-down strategy combined with quantitative proteomics to distinguish specific from nonspecific interactors, we identified 13,219 interactions involving 608 MRSA proteins. Consecutive analyses revealed that this protein interaction network (PIN) exhibits scale-free organization with the characteristic presence of highly connected hub proteins. When clinical and experimental antimicrobial targets were queried in the network, they were generally found to occupy peripheral positions in the PIN with relatively few interacting partners. In contrast, the hub proteins identified in this MRSA PIN that are essential for network integrity and stability have largely been overlooked as drug targets. Thus, this empirical MRSA-252 PIN provides a rich source for identifying critical proteins essential for network stability, many of which can be considered as prospective antimicrobial drug targets.

Identification of pyruvate kinase in methicillin-resistant Staphylococcus aureus as a novel antimicrobial drug target.

Novel classes of antimicrobials are needed to address the challenge of multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). Using the architecture of the MRSA interactome, we identified pyruvate kinase (PK) as a potential novel drug target based upon it being a highly connected, essential hub in the MRSA interactome. Structural modeling, including X-ray crystallography, revealed discrete features of PK in MRSA, which appeared suitable for the selective targeting of the bacterial enzyme. In silico library screening combined with functional enzymatic assays identified an acyl hydrazone-based compound (IS-130) as a potent MRSA PK inhibitor (50% inhibitory concentration [IC50] of 0.1 µM) with >1,000-fold selectivity over human PK isoforms. Medicinal chemistry around the IS-130 scaffold identified analogs that more potently and selectively inhibited MRSA PK enzymatic activity and S. aureus growth in vitro (MIC of 1 to 5 µg/ml). These novel anti-PK compounds were found to possess antistaphylococcal activity, including both MRSA and multidrug-resistant S. aureus (MDRSA) strains. These compounds also exhibited exceptional antibacterial activities against other Gram-positive genera, including enterococci and streptococci. PK lead compounds were found to be noncompetitive inhibitors and were bactericidal. In addition, mutants with significant increases in MICs were not isolated after 25 bacterial passages in culture, indicating that resistance may be slow to emerge. These findings validate the principles of network science as a powerful approach to identify novel antibacterial drug targets. They also provide a proof of principle, based upon PK in MRSA, for a research platform aimed at discovering and optimizing selective inhibitors of novel bacterial targets where human orthologs exist, as leads for anti-infective drug development.

Functional analysis, overexpression, and kinetic characterization of pyruvate kinase from methicillin-resistant Staphylococcus aureus.

Novel antimicrobial targets are urgently needed to overcome rising antibiotic resistance of important human pathogens including methicillin-resistant Staphylococcus aureus (MRSA). Here we report the essentiality and kinetic properties of MRSA pyruvate kinase (PK). Targetron-mediated gene disruption demonstrated PK is essential for S. aureus growth and survival, suggesting that this protein may be a potential drug target. The presence of the pfk (6-phosphofructokinase)-pyk operon in MRSA252, and the nonessential nature of PFK shown by targetron, further emphasized the essential role of PK in cell viability. The importance of PK in bacterial growth was confirmed by showing that its enzymatic activity peaked during the logarithmic phase of S. aureus growth. PK from Staphylococcus and several other species of bacteria have an extra C-terminal domain (CT) containing a phosphoenolpyruvate (PEP) binding motif. To elucidate the possible structure and function of this sequence, the quaternary structures and kinetic properties of the full-length MRSA PK and truncated MRSA PK lacking the CT domain were characterized. Our results showed that (1) MRSA PK is an allosteric enzyme with homotetramer architecture activated by AMP or ribose 5-phosphate (R5P), but not by fructose 1,6-bisphosphate (FBP), which suggests a different mode of allosteric regulation when compared with human isozymes, (2) the CT domain is not required for the tetramerization of the enzyme; homotetramerization occurred in a truncated PK lacking the domain, (3) truncated enzyme exhibited high affinity toward both PEP and ADP and exhibited hyperbolic kinetics toward PEP in the presence of activators (AMP and R5P) consistent with kinetic properties of full-length enzyme, indicating that the CT domain is not required for substrate binding or allosteric regulation observed in the holoenzyme, (4) the kinetic efficiency (k(cat)/S(0.5)) of truncated enzyme was decreased by 24- and 16-fold, in ligand-free state, toward PEP and ADP, respectively, but was restored by 3-fold in AMP-bound state, suggesting that the sequence containing the CT domain (Gly(473)-Leu(585)) plays a substantial role in enzyme activity and comformational stability, and (5) full-length MRSA PK activity was stimulated at low concentrations of ATP (e.g., 1 mM) and inhibited by inorganic phosphate and high concentrations of FBP (10 mM) and ATP (e.g., >2.5 mM), whereas for truncated enzyme, stimulation at low concentrations of ATP was lost. These findings suggest that the CT domain is involved in maintaining the specificity of allosteric regulation of MRSA PK by AMP, R5P, and ATP. The CT extension also encodes a protein domain with homology to enzyme I of the Escherichia coli sugar-PTS system, suggesting that MRSA PK may also exert an important regulatory role in sugar transport metabolism. These findings yield new insights into MRSA PK function and mode of allosteric regulation which may aid in the development of clinically important drugs targeting this enzyme and further define the role of the extra C-terminal domain in modulating the enzyme's activity.

Derivation of an induced pluripotent stem cell line (PUMCHi003-A) from a patient with pulmonary arterial hypertension carrying heterozygous mutation in PTGIS gene.

Pulmonary arterial hypertension (PAH) is a rare but severe illness associated with mutations in the PTGIS gene. The single nucleotide variants may lead to the impairment of the endothelial cells functions, resulting in proliferation of the smooth muscle cells and occlusion of the pulmonary arterioles. We derived an induced pluripotent cell line from a PAH patient with heterozygous PTGIS c.755 G > A, which could serve as a unique model to understand the pathogenesis of PAH.