Twisted graphene superlattices: resonating valence bond states and magnetic properties.

Resonating valence bond (RVB) states are fundamental for understanding quantum spin liquids in two-dimensional (2D) systems. The RVB state is a collective phenomenon in which spins are uncoupled. 2D lattices such as triangular, honeycomb, and dice lattices were investigated using the Hubbard model and exact diagonalization method. We analyzed the total spin, spin-spin correlation functions, local magnetic moments, and spin and charge gaps as a function of on-site Coulomb repulsion, electron concentration, and electronic hopping parameters. Phase diagrams showed that RVB states can live in half-filled and hole-doped anisotropic triangular lattices. We found two types of RVB states: one in the honeycomb sublattice and the other in the centered hexagons in the triangular lattices. Owing to the novel discovery of exotic magnetic ordering in triangular moiré patterns in twisted bilayer graphene and transition metal dichalcogenide systems, our results provide physical insights into the onset of magnetism and possible spin liquid states in these layered materials.

Thermodynamics of resonating-valence-bond states toward the understanding of quantum spin liquid phenomena.

A quantum spin liquid (QSL) is a state of matter in which spins do not exhibit magnetic order. In contrast to paramagnets, the spins in a QSL interact strongly, similar to conventional ordered magnets; however the thermodynamic stability of QSLs is rarely studied. Here, the thermodynamic properties of centered hexagon nanoclusters were investigated using the Hubbard model, which was solved using exact numerical diagonalization. The total spin, spin-spin correlation functions, local magnetic moments, charge and spin gaps, and magnetocaloric effect were analyzed for a half-filled band as a function of the ratio between the on-site Coulomb repulsion and electronic hopping (U/t). The centered hexagon nanocluster exhibited an antiferromagnetic (AFM) behavior with exotic magnetic ordering. Resonating-valence-bond (RVB) states were observed for intermediate values of U/t, in which short-range spin-spin correlation functions were suppressed to minimize spin frustration. The AFM order was examined in terms of the Néel-like temperature derived from the temperature dependence of the magnetic susceptibility. An interesting result is that the systems under external magnetic fields exhibited an inverse magnetocaloric effect, which was remarkable for intermediate values of U/t, where the RVB state was observed. Owing to the novel discovery of exotic magnetic ordering in triangular moiré patterns in twisted bilayer graphene (TBLG) systems, these results provide insights into the onset of magnetism and the possible spin liquid states in these graphene moiré materials.

Atomically Thin Current Pathways in Graphene through Kekulé-O Engineering.

We demonstrate that the current flow in graphene can be guided on atomically thin current pathways by the engineering of Kekulé-O distortions. A grain boundary in these distortions separates the system into topologically distinct regions and induces a ballistic domain-wall state. The state is independent of the orientation of the grain boundary with respect to the graphene sublattice and permits guiding the current on arbitrary paths. As the state is gapped, the current flow can be switched by electrostatic gates. Our findings are explained by a generalization of the Jackiw-Rebbi model, where the electrons behave in one region of the system as Fermions with an effective complex mass, making the device not only promising for technological applications but also a test-ground for concepts from high-energy physics. An atomic model supported by DFT calculations demonstrates that the system can be realized by decorating graphene with Ti atoms.

Biallelic hypomorphic variants in CAD cause uridine-responsive macrocytic anaemia with elevated haemoglobin-A2.

Biallelic pathogenic variants in CAD, that encode the multienzymatic protein required for de-novo pyrimidine biosynthesis, cause early infantile epileptic encephalopathy-50. This rare disease, characterized by developmental delay, intractable seizures and anaemia, is amenable to treatment with uridine. We present a patient with macrocytic anaemia, elevated haemoglobin-A2 levels, anisocytosis, poikilocytosis and target cells in the blood smear, and mild developmental delay. A next-generation sequencing panel revealed biallelic variants in CAD. Functional studies did not support complete abrogation of protein function; however, the patient responded to uridine supplement. We conclude that biallelic hypomorphic CAD variants may cause a primarily haematological phenotype.

An approach to investigate the crystallographic unit cell of human tooth enamel.

Human tooth enamel (HTE) is the hardest tissue in the human body and its structural organization shows a hierarchical composite material. At the nanometric level, HTE is composed of approximately 97% hydroxyapatite [HAP, Ca10(PO4)6(OH)2] as inorganic phase, and of 3% as organic phase and water. However, it is still controversial whether the hexagonal HAP phase crystallizes in P63/m or another space group. The observance in HTE of Ca2+, Mg2+ and Na+ ions using X-ray characteristic energy-dispersive spectroscopy in the scanning electron microscope has been explained by substitutions in the HAP unit cell. Thus, Ca2+ can be replaced by Na+ and Mg2+ ions; the PO43- group can be replaced by CO32- ions; and the OH- ions can also be replaced by CO32-. A unit-cell model of the hexagonal structure of HTE is not fully defined yet. In this work, density functional theory calculations are performed to study the hexagonal HAP unit cell when substitution by OH-, CO32-, Mg2+ and Na+ ions are carried out. An approach is presented to study the crystallographic unit cell of HTE by examining the changes resulting from the inclusion of these different ions in the unit cell of HAP. Enthalpies of formation and crystallographic characteristics of the electron diffraction patterns are analysed in each case. The results show an enhancement in structural stability of HAP with OH defects, atomic substitution of Mg2+, carbonate and interstitial Na+. Simulated electron diffraction patterns of the generated structures show similar characteristics to those of human tooth enamel. Hence, the results explain the indiscernible structural changes shown in experimental X-ray diffractograms and electron diffraction patterns.

Beyond genetics: Deciphering the impact of missense variants in CAD deficiency.

CAD is a large, 2225 amino acid multienzymatic protein required for de novo pyrimidine biosynthesis. Pathological CAD variants cause a developmental and epileptic encephalopathy which is highly responsive to uridine supplements. CAD deficiency is difficult to diagnose because symptoms are nonspecific, there is no biomarker, and the protein has over 1000 known variants. To improve diagnosis, we assessed the pathogenicity of 20 unreported missense CAD variants using a growth complementation assay that identified 11 pathogenic variants in seven affected individuals; they would benefit from uridine treatment. We also tested nine variants previously reported as pathogenic and confirmed the damaging effect of seven. However, we reclassified two variants as likely benign based on our assay, which is consistent with their long-term follow-up with uridine. We found that several computational methods are unreliable predictors of pathogenic CAD variants, so we extended the functional assay results by studying the impact of pathogenic variants at the protein level. We focused on CAD's dihydroorotase (DHO) domain because it accumulates the largest density of damaging missense changes. The atomic-resolution structures of eight DHO pathogenic variants, combined with functional and molecular dynamics analyses, provided a comprehensive structural and functional understanding of the activity, stability, and oligomerization of CAD's DHO domain. Combining our functional and protein structural analysis can help refine clinical diagnostic workflow for CAD variants in the genomics era.

A Tailored Strategy to Crosslink the Aspartate Transcarbamoylase Domain of the Multienzymatic Protein CAD.

CAD is a 1.5 MDa hexameric protein with four enzymatic domains responsible for initiating de novo biosynthesis of pyrimidines nucleotides: glutaminase, carbamoyl phosphate synthetase, aspartate transcarbamoylase (ATC), and dihydroorotase. Despite its central metabolic role and implication in cancer and other diseases, our understanding of CAD is poor, and structural characterization has been frustrated by its large size and sensitivity to proteolytic cleavage. Recently, we succeeded in isolating intact CAD-like particles from the fungus Chaetomium thermophilum with high yield and purity, but their study by cryo-electron microscopy is hampered by the dissociation of the complex during sample grid preparation. Here we devised a specific crosslinking strategy to enhance the stability of this mega-enzyme. Based on the structure of the isolated C. thermophilum ATC domain, we inserted by site-directed mutagenesis two cysteines at specific locations that favored the formation of disulfide bridges and covalent oligomers. We further proved that this covalent linkage increases the stability of the ATC domain without damaging the structure or enzymatic activity. Thus, we propose that this cysteine crosslinking is a suitable strategy to strengthen the contacts between subunits in the CAD particle and facilitate its structural characterization.

Ruptura uterina espontánea e inadvertida. Reporte de caso / Spontaneous and undetected uterine rupture. Case report

Resumen ANTECEDENTES: La ruptura uterina es la separación de las tres capas del útero que se asocia con una cicatriz. La mayoría de los casos se relacionan con intento de trabajo de parto, después de una cesárea. La ruptura es una complicación grave, que pone en riesgo a la madre y al feto. De forma excepcional puede haber ruptura uterina sin síntomas, y el hallazgo se advierte durante la cesárea de repetición. CASO CLÍNICO: Paciente de 27 años, programada para cesárea de repetición por disfunción de una prótesis valvular. A la apertura de la cavidad abdominal no se encontró hemoperitoneo y se visualizó un defecto transverso en el segmento uterino inferior de las tres capas uterinas, con saco amniótico íntegro, coincidente con ruptura uterina. Se obtuvo un recién nacido sano, de 2610 g y Apgar de 9-9. La herida uterina se suturó en dos planos y se practicó la oclusión tubaria bilateral. La evolución durante el puerperio fue satisfactoria. CONCLUSIONES: La ruptura uterina puede pasar inadvertida por algún descuido en la historia clínica y ausculatación, de ahí la necesidad de ser más minuciosos para poder indicar el tratamiento adecuado.

Abstract BACKGROUND: Uterine rupture is a separation of the three layers of the uterus and is associated with a uterine scar. Most cases are related to an attempted labor after a cesarean section. Uterine rupture is a serious complication that puts both mother and fetus at risk. Exceptionally uterine rupture can occur without symptoms, being a finding during a repeat cesarean section. CLINICAL CASE: A 27-year-old patient scheduled for repeat cesarean section due to dysfunction of a prosthetic valve. Upon opening the abdominal cavity, no hemoperitoneum was found and a transverse defect was visualized in the lower uterine segment of the three uterine layers, with an intact amniotic sac, coinciding with uterine rupture. A healthy newborn was obtained, weighing 2610 g and Apgar 9-9. The uterine wound was sutured in two planes and bilateral tubal occlusion was performed. The evolution during the puerperium was satisfactory. CONCLUSIONS: Uterine rupture may go unnoticed due to an oversight in the clinical history and auscultation, hence the need to be more thorough in order to indicate appropriate treatment.

Síndrome de Klippel Trenaunay y embarazo. Reporte de tres casos / Klippel-Trenaunay syndrome and pregnancy. Report of three cases

Resumen ANTECEDENTES: El síndrome de Klippel Trenaunay es una enfermedad congénita rara, caracterizada por malformaciones capilares y venosas, sobrecrecimiento de miembros y en algunos casos malformaciones linfáticas. Quienes lo padecen tienen un riesgo incrementado de hemorragia y tromboembolismo. CASOS CLÍNICOS: Tres pacientes primigestas con diagnóstico de síndrome de Klippel Trenaunay con complicaciones del embarazo que finalizaron mediante cesárea con el nacimiento de sus hijos sanos, de término, en todos los casos. CONCLUSIONES: Las embarazadas y con síndrome de Klippel-Trenaunay tienen un riesgo significativo de que sus síntomas se agraven, de tener hemorragia durante el nacimiento y de eventos tromboembólicos, incluso después del nacimiento. La atención individualizada y multidisciplinaria ayudará a mitigar las complicaciones asociadas y a conseguir desenlaces óptimos.

Abstract BACKGROUND: Klippel Trenaunay syndrome is a rare congenital disease characterized by capillary and venous malformations, limb overgrowth and in some cases lymphatic malformations. Sufferers have an increased risk of hemorrhage and thromboembolism. CLINICAL CASES: Three primigravid patients diagnosed with Klippel Trenaunay syndrome with pregnancy complications that were terminated by cesarean section with the birth of their healthy, full-term children in all cases. CONCLUSIONS: Women with Klippel-Trenaunay syndrome and pregnancy are at significant risk for aggravation of their symptoms, hemorrhage during birth, and thromboembolic events, even after birth. Individualized, multidisciplinary care will help mitigate associated complications and achieve optimal outcomes.

Epidermólisis bulosa distrófica recesiva en mujer embarazada. Reporte de caso / Recessive dystrophic epidermolysis bullosa in pregnant women. Case report

Resumen INTRODUCCIÓN: La epidermólisis bulosa engloba a un grupo de enfermedades caracterizadas por una fragilidad extrema de la piel y membranas mucosas, consecuencia de la formación de ampollas posterior a un traumatismo mínimo. Hay tres tipos principales de epidermólisis. Se comunica el caso para hacer notar las implicaciones del cuidado al momento del nacimiento, y las consideraciones anestésicas. CASO CLÍNICO: Paciente de 25 años en su segundo embarazo con epidermólisis bulosa distrófica recesiva. El nacimiento fue electivo mediante cesárea, con anestesia regional. CONCLUSIONES: Debe tenerse especial cuidado durante las intervenciones terapéuticas a fin de evitar la formación de bulas o exacerbar las existentes. Las fuerzas de fricción son más dañinas que las de compresión. La planeación multidisciplinaria es necesaria para un desenlace sin complicaciones.

Abstract BACKGROUND: Epidermolysis bullosa encompasses a group of diseases characterized by extreme fragility of the skin and mucous membranes, resulting in the formation of blisters after minimal trauma; There are three main types of epidermolysis. The case is presented to highlight the implications of care both at the time of birth, as well as anesthetic considerations. CLINICAL CASE: A 25-year-old patient in her second pregnancy with recessive dystrophic epidermolysis bullosa. The birth was elective by caesarean section under regional anesthesia. CONCLUSIONS: Special care must be taken during therapeutic interventions to avoid the formation of bullae or exacerbate those already present. Friction forces are more damaging than compression forces. Multidisciplinary planning is necessary for a smooth outcome.

Síndrome de Andersen Tawil en una embarazada con alto riesgo de muerte súbita. Reporte de caso / Andersen Tawil syndrome in a pregnant woman at high risk of sudden death

Resumen ANTECEDENTES: El síndrome de Andersen Tawil es una canalopatía multisistémica genética, muy rara, sin alteración cardiaca estructural, heredada de manera autosómica dominante y causada por mutación en el gen KCNJ2. Este síndrome se caracteriza por una triada de parálisis muscular periódica, cambios en el electrocardiograma y estructurales corporales. El rasgo distintivo es la taquicardia ventricular bidireccional, las contracciones ventriculares prematuras y raramente taquicardia polimórfica tipo torsade de pointes. En la actualidad se carece de guías para el peri y postparto y para la prevención de arritmias. CASO CLÍNICO: Paciente de 21 años, embarazada, con síndrome de Andersen Tawil diagnosticado a esta edad, con base en los antecedentes de síncope de repetición y debilidad en las extremidades desde los 11 años. Recibía tratamiento con un beta-bloqueador y un desfibrilador automático implantable. La ecocardiografía fetal a las 23 y 33 semanas de gestación reportó una comunicación interventricular apical de 1.6 mm. A las 39 semanas de embarazo se practicó una cesárea electiva, con evolución posoperatoria satisfactoria. El estudio molecular dirigido al recién nacido descartó el síndrome de Andersen Tawil congénito. CONCLUSIÓN: En pacientes con síndromes de arritmia congénita, el embarazo puede ser seguro siempre y cuando un grupo de especialistas esté pendiente para tomar decisiones de atención y tratamiento durante todo el proceso del embarazo y puerperio.

Abstract BACKGROUND: Andersen Tawil syndrome is a very rare genetic multisystemic channelopathy without structural cardiac alteration, inherited in an autosomal dominant manner and caused by mutation in the KCNJ2 gene. This syndrome is characterised by a triad of periodic muscle paralysis, electrocardiogram and body structural changes. The hallmark is bidirectional ventricular tachycardia, premature ventricular contractions and rarely polymorphic torsade de pointes tachycardia. Currently there is a lack of guidelines for peri- and postpartum and arrhythmia prevention. CLINICAL CASE: 21-year-old pregnant patient with Andersen-Tawil syndrome diagnosed at this age, based on a history of repeated syncope and weakness in the extremities since the age of 11. She was being treated with a beta-blocker and an implantable cardioverter defibrillator. Fetal echocardiography at 23 and 33 weeks gestation reported an apical ventricular septal defect of 1.6 mm. Elective caesarean section was performed at 39 weeks of pregnancy, with satisfactory postoperative evolution. Molecular study of the newborn ruled out congenital Andersen-Tawil syndrome. CONCLUSION: In patients with congenital arrhythmia syndromes, pregnancy can be safe as long as it is managed by a group of experts to make decisions and optimise care throughout the pregnancy and postpartum period.

Phosphorylation of T897 in the dimerization domain of Gemin5 modulates protein interactions and translation regulation.

Gemin5 is a multifunctional RNA binding protein (RBP) organized in domains with a distinctive structural organization. The protein is a hub for several protein networks performing diverse RNA-dependent functions including regulation of translation, and recognition of small nuclear RNAs (snRNAs). Here we sought to identify the presence of phosphoresidues on the C-terminal half of Gemin5, a region of the protein that harbors a tetratricopeptide repeat (TPR)-like dimerization domain and a non-canonical RNA binding site (RBS1). We identified two phosphoresidues in the purified protein: P-T897 in the dimerization domain and P-T1355 in RBS1. Replacing T897 and T1355 with alanine led to decreased translation, and mass spectrometry analysis revealed that mutation T897A strongly abrogates the association with cellular proteins related to the regulation of translation. In contrast, the phosphomimetic substitutions to glutamate partially rescued the translation regulatory activity. The structural analysis of the TPR dimerization domain indicates that local rearrangements caused by phosphorylation of T897 affect the conformation of the flexible loop 2-3, and propagate across the dimerization interface, impacting the position of the C-terminal helices and the loop 12-13 shown to be mutated in patients with neurological disorders. Computational analysis of the potential relationship between post-translation modifications and currently known pathogenic variants indicates a lack of overlapping of the affected residues within the functional domains of the protein and provides molecular insights for the implication of the phosphorylated residues in translation regulation.

A functional platform for the selection of pathogenic variants of PMM2 amenable to rescue via the use of pharmacological chaperones.

Different strategies are being investigated for treating PMM2-CDG, the most common congenital disorder of glycosylation. The use of pharmacochaperones (PCs) is one of the most promising. The present work characterizes the expression, stability, and enzymatic properties of 15 previously described clinical variants of the PMM2 protein, four novel variants, the Pmm2 mouse variant p.Phe115Leu, and its p.Phe119Leu human counterpart, with the aim of extending the potential use of pharmacochaperoning treatment. PMM2 variants were purified as stable homodimers, except for p.Asp65Gly, p.Ile120Thr, and p.Thr237Lys (no expression detected), p.Thr226Ser and p.Val231Met (aggregates), and p.Glu93Ala, p.Phe119Leu, and p.Phe115Leu (partial dissociated). Enzyme activity analyses identified severe variants and milder ones. Pure dimeric mutant proteins showed a reduction in thermal stability except for p.Asn216Asp. The thermal stability of all the unstable mutants was recovered in the presence of the PC compound VIII. This study adds to the list of destabilizing human variants amenable to rescue by small chemical compounds that increase the stability/activity of PMM2. The proposed platform can be reliably used for assessing the disease-causing effects of PMM2 missense variants, for assessing the correlation between genotype and phenotype, for confirming new clinical defects, and for identifying destabilizing mutations amenable to rescue by PCs.

Resistin Modulates Low-Density Lipoprotein Cholesterol Uptake in Human Placental Explants via PCSK9.

Maternal metabolic status influences pregnancy and, consequently, the perinatal outcome. Resistin is a pro-inflammatory adipokine predominantly expressed and secreted by mononuclear cells, adipose tissue, and placental trophoblastic cells during pregnancy. Recently, we reported an inverse association between maternal resistin levels and fetal low-density lipoprotein cholesterol (LDL-C). Then, in this work, we used a human placental explant model and the trophoblast cell line JEG-3 to evaluate whether resistin affects placental LDL-C uptake. Resistin exposure induced the transcription factor SREBP-2, LDLR, and PCSK9 mRNA expression, and changes at the protein level were confirmed by immunohistochemistry and Western blot. However, for LDLR, the changes were not consistent between mRNA and protein levels. Using a labeled LDL-cholesterol (BODIPY FL LDL), uptake assay demonstrated that the LDL-C was significantly decreased in placental explants exposed to a high dose of resistin and a lesser extent in JEG-3 cells. In summary, resistin induces PCSK9 expression in placental explants and JEG-3 cells, which could be related to negative regulation of the LDLR by lysosomal degradation. These findings suggest that resistin may significantly regulate the LDL-C uptake and transport from the maternal circulation to the fetus, affecting its growth and lipid profile.

Functional and structural deficiencies of Gemin5 variants associated with neurological disorders.

Dysfunction of RNA-binding proteins is often linked to a wide range of human disease, particularly with neurological conditions. Gemin5 is a member of the survival of the motor neurons (SMN) complex, a ribosome-binding protein and a translation reprogramming factor. Recently, pathogenic mutations in Gemin5 have been reported, but the functional consequences of these variants remain elusive. Here, we report functional and structural deficiencies associated with compound heterozygosity variants within the Gemin5 gene found in patients with neurodevelopmental disorders. These clinical variants are located in key domains of Gemin5, the tetratricopeptide repeat (TPR)-like dimerization module and the noncanonical RNA-binding site 1 (RBS1). We show that the TPR-like variants disrupt protein dimerization, whereas the RBS1 variant confers protein instability. All mutants are defective in the interaction with protein networks involved in translation and RNA-driven pathways. Importantly, the TPR-like variants fail to associate with native ribosomes, hampering its involvement in translation control and establishing a functional difference with the wild-type protein. Our study provides insights into the molecular basis of disease associated with malfunction of the Gemin5 protein.

Fundamentos de la cobertura universal en servicios de salud / Foundations of universal coverage in health services

Desde hace varias décadas se debate con frecuencia el tema de la cobertura y acceso a los servicios de salud. El objetivo de la presente comunicación es contribuir al debate partiendo de las experiencias concretas del Sistema Nacional de Salud de Cuba en las últimas seis décadas. Se realizó una revisión bibliográfica y de documentos oficiales del Sistema Nacional de Salud cubano. Se presenta una síntesis breve de la experiencia cubana. Se puede decir que Cuba alcanzó la cobertura universal alrededor de 2010-2015 con el modelo del médico y enfermera de la familia(AU)

For several decades, the issue of coverage and access to health services has been frequently debated. The objective of this communication is to contribute to the debate based on the concrete experiences of the Cuban National Health System in the last six decades. A bibliographic and official document review of the Cuban National Health System was carried out. A brief synthesis of the Cuban experience is presented. It can be said that Cuba reached universal coverage around 2010-2015 with the model of the family doctor and nurse(AU)

Insight on molecular pathogenesis and pharmacochaperoning potential in phosphomannomutase 2 deficiency, provided by novel human phosphomannomutase 2 structures.

Phosphomannomutase 2 (PMM2) deficiency, the most frequent congenital disorder of glycosylation (PMM2-CDG), is a severe condition, which has no cure. Due to the identification of destabilizing mutations, our group aims at increasing residual activity in PMM2-CDG patients, searching for pharmacochaperones. Detailed structural knowledge of hPMM2 might help identify variants amenable to pharmacochaperoning. hPMM2 structural information is limited to one incomplete structure deposited in the Protein Databank without associated publication, which lacked ligands and residues from a crucial loop. Here we report five complete crystal structures of hPMM2, three for wild-type and two for the p.Thr237Met variant frequently found among Spanish PMM2-CDG patients, free and bound to the essential activator glucose-1,6-bisphosphate (Glc-1,6-P2 ). In the hPMM2 homodimer, each subunit has a different conformation, reflecting movement of the distal core domain relative to the dimerization cap domain, supporting an opening/closing process during catalysis. Two Mg2+ ions bind to the core domain, one catalytic and one structural. In the cap domain, the site for Glc-1,6-P2 is well delineated, while a Cl- ion binding at the intersubunit interface is predicted to strengthen dimerization. Patient-found amino acid substitutions are nonhomogeneously distributed throughout hPMM2, reflecting differential functional or structural importance for various parts of the protein. We classify 93 of 101 patient-reported single amino acid variants according to five potential pathogenetic mechanism affecting folding of the core and cap domains, linker 2 flexibility, dimerization, activator binding, and catalysis. We propose that ~80% and ~50% of the respective core and cap domains substitutions are potential candidates for pharmacochaperoning treatment.

Deciphering CAD: Structure and function of a mega-enzymatic pyrimidine factory in health and disease.

CAD is a 1.5 MDa particle formed by hexameric association of a 250 kDa protein divided into different enzymatic domains, each catalyzing one of the initial reactions for de novo biosynthesis of pyrimidine nucleotides: glutaminase-dependent Carbamoyl phosphate synthetase, Aspartate transcarbamoylase, and Dihydroorotase. The pathway for de novo pyrimidine synthesis is essential for cell proliferation and is conserved in all living organisms, but the covalent linkage of the first enzymatic activities into a multienzymatic CAD particle is unique to animals. In other organisms, these enzymatic activities are encoded as monofunctional proteins for which there is abundant structural and biochemical information. However, the knowledge about CAD is scarce and fragmented. Understanding CAD requires not only to determine the three-dimensional structures and define the catalytic and regulatory mechanisms of the different enzymatic domains, but also to comprehend how these domains entangle and work in a coordinated and regulated manner. This review summarizes significant progress over the past 10 years toward the characterization of CAD's architecture, function, regulatory mechanisms, and cellular compartmentalization, as well as the recent finding of a new and rare neurometabolic disorder caused by defects in CAD activities.

Modeling the aluminum-doped and single vacancy blue phosphorene interactions with molecules: a density functional theory study.

Structural, electronic, binding energies and magnetic properties of aluminum-doped and single vacancy blue phosphorene interacting with pollutant molecules are investigated using the density functional theory (DFT) with periodic boundary conditions. Acetylene, ozone, sulfur trioxide, hydrogen selenide, and sulfur dichloride molecules are considered to show the efficiency and enhancement of the sensing properties in comparison with the pristine blue phosphorene. Acetylene, sulfur trioxide, hydrogen selenide, and sulfur dichloride show chemisorption (> 0.5 eV/molecule) when interacting with the aluminum-doped system, but the ozone molecule dissociates in all configurations and symmetry sites. On the other hand, the acetylene, ozone, and sulfur trioxide with the single vacancy blue phosphorene exhibit chemisorption, the hydrogen selenide molecule exhibit a weak interaction energy, and the sulfur dichloride dissociates in all configurations and symmetry sites. In all the cases, the enhancement in the interaction energy was achieved when compared to other results for the same molecules. Finally, the single vacancy blue phosphorene shows a magnetic moment of ~1 µB/supercell, as induced by the vacancy.

Afatinib Exerts Immunomodulatory Effects by Targeting the Pyrimidine Biosynthesis Enzyme CAD.

Current clinical trials of combined EGFR-tyrosine kinase inhibitors (TKI) and immune checkpoint blockade (ICB) therapies show no additional effect. This raises questions regarding whether EGFR-TKIs attenuate ICB-enhanced CD8+ T lymphocyte function. Here we show that the EGFR-TKI afatinib suppresses CD8+ T lymphocyte proliferation, and we identify CAD, a key enzyme of de novo pyrimidine biosynthesis, to be a novel afatinib target. Afatinib reduced tumor-infiltrating lymphocyte numbers in Lewis lung carcinoma (LLC)-bearing mice. Early afatinib treatment inhibited CD8+ T lymphocyte proliferation in patients with non-small cell lung cancer, but their proliferation unexpectedly rebounded following long-term treatment. This suggests a transient immunomodulatory effect of afatinib on CD8+ T lymphocytes. Sequential treatment of afatinib with anti-PD1 immunotherapy substantially enhanced therapeutic efficacy in MC38 and LLC-bearing mice, while simultaneous combination therapy showed only marginal improvement over each single treatment. These results suggest that afatinib can suppress CD8+ T lymphocyte proliferation by targeting CAD, proposing a timing window for combined therapy that may prevent the dampening of ICB efficacy by EGFR-TKIs. SIGNIFICANCE: This study elucidates a mechanism of afatinib-mediated immunosuppression and provides new insights into treatment timing for combined targeted therapy and immunotherapy. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/12/3270/F1.large.jpg.