An enzyme that selectively S-nitrosylates proteins to regulate insulin signaling.

Acyl-coenzyme A (acyl-CoA) species are cofactors for numerous enzymes that acylate thousands of proteins. Here, we describe an enzyme that uses S-nitroso-CoA (SNO-CoA) as its cofactor to S-nitrosylate multiple proteins (SNO-CoA-assisted nitrosylase, SCAN). Separate domains in SCAN mediate SNO-CoA and substrate binding, allowing SCAN to selectively catalyze SNO transfer from SNO-CoA to SCAN to multiple protein targets, including the insulin receptor (INSR) and insulin receptor substrate 1 (IRS1). Insulin-stimulated S-nitrosylation of INSR/IRS1 by SCAN reduces insulin signaling physiologically, whereas increased SCAN activity in obesity causes INSR/IRS1 hypernitrosylation and insulin resistance. SCAN-deficient mice are thus protected from diabetes. In human skeletal muscle and adipose tissue, SCAN expression increases with body mass index and correlates with INSR S-nitrosylation. S-nitrosylation by SCAN/SNO-CoA thus defines a new enzyme class, a unique mode of receptor tyrosine kinase regulation, and a revised paradigm for NO function in physiology and disease.

S-nitrosylation is required for ß2AR desensitization and experimental asthma.

The ß2-adrenergic receptor (ß2AR), a prototypic G-protein-coupled receptor (GPCR), is a powerful driver of bronchorelaxation, but the effectiveness of ß-agonist drugs in asthma is limited by desensitization and tachyphylaxis. We find that during activation, the ß2AR is modified by S-nitrosylation, which is essential for both classic desensitization by PKA as well as desensitization of NO-based signaling that mediates bronchorelaxation. Strikingly, S-nitrosylation alone can drive ß2AR internalization in the absence of traditional agonist. Mutant ß2AR refractory to S-nitrosylation (Cys265Ser) exhibits reduced desensitization and internalization, thereby amplifying NO-based signaling, and mice with Cys265Ser mutation are resistant to bronchoconstriction, inflammation, and the development of asthma. S-nitrosylation is thus a central mechanism in ß2AR signaling that may be operative widely among GPCRs and targeted for therapeutic gain.

Author Correction: Metabolic reprogramming by the S-nitroso-CoA reductase system protects against kidney injury.

Change history: In Fig. 1j of this Letter, one data point was inadvertently omitted from the graph for the acute kidney injury (AKI), double knockout (-/-), S-nitrosothiol (SNO) condition at a nitrosylation level of 25.9 pmol mg-1 and the statistical significance given of P = 0.0221 was determined by Fisher's test instead of P = 0.0032 determined by Tukey's test (with normalization for test-day instrument baseline). Figure 1 and its Source Data have been corrected online.

Metabolic reprogramming by the S-nitroso-CoA reductase system protects against kidney injury.

Endothelial nitric oxide synthase (eNOS) is protective against kidney injury, but the molecular mechanisms of this protection are poorly understood1,2. Nitric oxide-based cellular signalling is generally mediated by protein S-nitrosylation, the oxidative modification of Cys residues to form S-nitrosothiols (SNOs). S-nitrosylation regulates proteins in all functional classes, and is controlled by enzymatic machinery that includes S-nitrosylases and denitrosylases, which add and remove SNO from proteins, respectively3,4. In Saccharomyces cerevisiae, the classic metabolic intermediate co-enzyme A (CoA) serves as an endogenous source of SNOs through its conjugation with nitric oxide to form S-nitroso-CoA (SNO-CoA), and S-nitrosylation of proteins by SNO-CoA is governed by its cognate denitrosylase, SNO-CoA reductase (SCoR)5. Mammals possess a functional homologue of yeast SCoR, an aldo-keto reductase family member (AKR1A1)5 with an unknown physiological role. Here we report that the SNO-CoA-AKR1A1 system is highly expressed in renal proximal tubules, where it transduces the activity of eNOS in reprogramming intermediary metabolism, thereby protecting kidneys against acute kidney injury. Specifically, deletion of Akr1a1 in mice to reduce SCoR activity increased protein S-nitrosylation, protected against acute kidney injury and improved survival, whereas this protection was lost when Enos (also known as Nos3) was also deleted. Metabolic profiling coupled with unbiased mass spectrometry-based SNO-protein identification revealed that protection by the SNO-CoA-SCoR system is mediated by inhibitory S-nitrosylation of pyruvate kinase M2 (PKM2) through a novel locus of regulation, thereby balancing fuel utilization (through glycolysis) with redox protection (through the pentose phosphate shunt). Targeted deletion of PKM2 from mouse proximal tubules recapitulated precisely the protective and mechanistic effects of S-nitrosylation in Akr1a1-/- mice, whereas Cys-mutant PKM2, which is refractory to S-nitrosylation, negated SNO-CoA bioactivity. Our results identify a physiological function of the SNO-CoA-SCoR system in mammals, describe new regulation of renal metabolism and of PKM2 in differentiated tissues, and offer a novel perspective on kidney injury with therapeutic implications.

Activation of hepatic acetyl-CoA carboxylase by S-nitrosylation in response to diet.

Nitric oxide (NO), produced primarily by nitric oxide synthase enzymes, is known to influence energy metabolism by stimulating fat uptake and oxidation. The effects of NO on de novo lipogenesis (DNL), however, are less clear. Here we demonstrate that hepatic expression of endothelial nitric oxide synthase is reduced following prolonged administration of a hypercaloric high-fat diet. This results in marked reduction in the amount of S-nitrosylation of liver proteins including notably acetyl-CoA carboxylase (ACC), the rate-limiting enzyme in DNL. We further show that ACC S-nitrosylation markedly increases enzymatic activity. Diminished endothelial nitric oxide synthase expression and ACC S-nitrosylation may thus represent a physiological adaptation to caloric excess by constraining lipogenesis. Our findings demonstrate that S-nitrosylation of liver proteins is subject to dietary control and suggest that DNL is coupled to dietary and metabolic conditions through ACC S-nitrosylation.

Physiological role for S-nitrosylation of RyR1 in skeletal muscle function and development.

Excitation-contraction coupling in skeletal muscle myofibers depends upon Ca2+ release from the sarcoplasmic reticulum through the ryanodine receptor/Ca2+-release channel RyR1. The RyR1 contains ∼100 Cys thiols of which ∼30 comprise an allosteric network subject to posttranslational modification by S-nitrosylation, S-palmitoylation and S-oxidation. However, the role and function of these modifications is not understood. Although aberrant S-nitrosylation of multiple unidentified sites has been associated with dystrophic diseases, malignant hyperthermia and other myopathic syndromes, S-nitrosylation in physiological situations is reportedly specific to a single (1 of ∼100) Cys in RyR1, Cys3636 in a manner gated by pO2. Using mice expressing a form of RyR1 with a Cys3636→Ala point mutation to prevent S-nitrosylation at this site, we showed that Cys3636 was the principal target of endogenous S-nitrosylation during normal muscle function. The absence of Cys3636 S-nitrosylation suppressed stimulus-evoked Ca2+ release at physiological pO2 (at least in part by altering the regulation of RyR1 by Ca2+/calmodulin), eliminated pO2 coupling, and diminished skeletal myocyte contractility in vitro and measures of muscle strength in vivo. Furthermore, we found that abrogation of Cys3636 S-nitrosylation resulted in a developmental defect reflected in diminished myofiber diameter, altered fiber subtypes, and altered expression of genes implicated in muscle development and atrophy. Thus, our findings establish a physiological role for pO2-coupled S-nitrosylation of RyR1 in skeletal muscle contractility and development and provide foundation for future studies of RyR1 modifications in physiology and disease.

A Hybrid Model for Fetal Growth Restriction Assessment by Automatic Placental Radiomics on T2-Weighted MRI and Multifeature Fusion.

BACKGROUND: MRI-based placental analyses have been used to improve fetal growth restriction (FGR) assessment by complementing ultrasound-based measurements. However, these are still limited by time-consuming manual annotation in MRI data and the lack of mother-based information. PURPOSE: To develop and validate a hybrid model for accurate FGR assessment by automatic placental radiomics on T2-weighted imaging (T2WI) and multifeature fusion. STUDY TYPE: Retrospective. POPULATION: 274 pregnant women (29.5 ± $$ \pm $$ 4.0 years) from two centers were included and randomly divided into training (N = 119), internal test (N = 40), time-independent validation (N = 43), and external validation (N = 72) sets. FIELD STRENGTH/SEQUENCE: 1.5-T, T2WI half-Fourier acquisition single-shot turbo spin-echo pulse sequence. ASSESSMENT: First, the placentas on T2WI were manually annotated, and a deep learning model was developed to automatically segment the placentas. Then, the radiomic features were extracted from the placentas and selected by three-step feature selection. In addition, fetus-based measurement features and mother-based clinical features were obtained from ultrasound examinations and medical records, respectively. Finally, a hybrid model based on random forest was constructed by fusing these features, and further compared with models based on other machine learning methods and different feature combinations. STATISTICAL TESTS: The performances of placenta segmentation and FGR assessment were evaluated by Dice similarity coefficient (DSC) and the area under the receiver operating characteristic curve (AUROC), respectively. A P-value <0.05 was considered statistically significant. RESULTS: The placentas were automatically segmented with an average DSC of 90.0%. The hybrid model achieved an AUROC of 0.923, 0.931, and 0.880 on the internal test, time-independent validation, and external validation sets, respectively. The mother-based clinical features resulted in significant performance improvements for FGR assessment. DATA CONCLUSION: The proposed hybrid model may be able to assess FGR with high accuracy. Furthermore, information complementation based on placental, fetal, and maternal features could also lead to better FGR assessment performance. TECHNICAL EFFICACY: Stage 2.

Optimized S-nitrosohemoglobin Synthesis in Red Blood Cells to Preserve Hypoxic Vasodilation Via ßCys93.

Classic physiology links tissue hypoxia to oxygen delivery through control of microvascular blood flow (autoregulation of blood flow). Hemoglobin (Hb) serves both as the source of oxygen and the mediator of microvascular blood flow through its ability to release vasodilatory S-nitrosothiol (SNO) in proportion to degree of hypoxia. ß-globin Cys93Ala (ßCys93Ala) mutant mice deficient in S-nitrosohemoglobin (SNO-Hb) show profound deficits in microvascular blood flow and tissue oxygenation that recapitulate microcirculatory dysfunction in multiple clinical conditions. However, the means to replete SNO in mouse red blood cells (RBCs) to restore RBC function is not known. In particular, although methods have been developed to selectively S-nitrosylate ßCys93 in human Hb and intact human RBCs, conditions have not been optimized for mouse RBCs that are used experimentally. Here we show that loading SNO onto Hb in mouse RBC lysates can be achieved with high stoichiometry and ß-globin selectivity. However, S-nitrosylation of Hb within intact mouse RBCs is ineffective under conditions that work well with human RBCs, and levels of metHb are prohibitively high. We developed an optimized method that loads SNO in mouse RBCs to maintain vasodilation under hypoxia and shows that loss of SNO loading in ßCys93Ala mutant RBCs results in reduced vasodilation. We also demonstrate that differences in SNO/met/nitrosyl Hb stoichiometry can account for differences in RBC function among studies. RBCs loaded with quasi-physiologic amounts of SNO-Hb will produce vasodilation proportionate to hypoxia, whereas RBCs loaded with higher amounts lose allosteric regulation, thus inducing vasodilation at both high and low oxygen level. SIGNIFICANCE STATEMENT: Red blood cells from mice exhibit poor hemoglobin S-nitrosylation under conditions used for human RBCs, frustrating tests of vasodilatory activity. Using an optimized S-nitrosylation protocol, mouse RBCs exhibit hypoxic vasodilation that is significantly reduced in hemoglobin ßCys93Ala mutant RBCs that cannot carry S-nitrosothiol allosterically, providing genetic validation for the role of ßCys93 in oxygen delivery.

Age-specific structural fetal brain atlases construction and cortical development quantification for chinese population.

In magnetic resonance imaging (MRI) studies of fetal brain development, structural brain atlases usually serve as essential references for the fetal population. Individual images are usually normalized into a common or standard space for analysis. However, the existing fetal brain atlases are mostly based on MR images obtained from Caucasian populations and thus are not ideal for the characterization of the fetal Chinese population due to neuroanatomical differences related to genetic factors. In this paper, we use an unbiased template construction algorithm to create a set of age-specific Chinese fetal atlases between 21-35 weeks of gestation from 115 normal fetal brains. Based on the 4D spatiotemporal atlas, the morphological development patterns, e.g., cortical thickness, cortical surface area, sulcal and gyral patterns, were quantified. The fetal brain abnormalities were detected when referencing the age-specific template. Additionally, a direct comparison of the Chinese fetal atlases and Caucasian fetal atlases reveals dramatic anatomical differences, mainly in the medial frontal and temporal regions. After applying the Chinese and Caucasian fetal atlases separately to an independent Chinese fetal brain dataset, we find that the Chinese fetal atlases result in significantly higher accuracy than the Caucasian fetal atlases in guiding brain tissue segmentation. These results suggest that the Chinese fetal brain atlases are necessary for quantitative analysis of the typical and atypical development of the Chinese fetal population in the future. The atlases with their parcellations are now publicly available at https://github.com/DeepBMI/FBA-Chinese.

Probing the ballistic microcirculation in placenta using flow-compensated and non-compensated intravoxel incoherent motion imaging.

PURPOSE: Intravoxel incoherent motion (IVIM) imaging is widely used to evaluate microcirculatory flow, which consists of diffusive and ballistic flow components. We proposed a joint use of flow-compensated (FC) and non-compensated (NC) diffusion gradients to probe the fraction and velocity of ballistic flow in the placenta. METHODS: Forty pregnant women were included in this study and scanned on a 1.5T clinical scanner. FC and NC diffusion MRI (dMRI) sequences were achieved using a pair of identical or mirrored bipolar gradients. A joint FC-NC model was established to estimate the fraction (fb ) and velocity (vb ) of the ballistic flow. Conventional IVIM parameters (f, D, and D*) were obtained from the FC and NC data, separately. The vb and f·D*, as placental flow velocity measurements, were correlated with the umbilical-artery Doppler ultrasound indices and gestational ages. RESULTS: The ballistic flow component can be observed from the difference between the FC and NC dMRI signal decay curves. vb fitted from the FC-NC model showed strong correlations with umbilical-artery impedance indices, the systolic-to-diastolic (SD) ratio and pulsatility index (PI), with correlation coefficients of 0.65 and 0.62. The f·D* estimated from the NC data positively correlated with SD and PI, while the FC-based f·D* values showed weak negative correlations. Significant gestational-age dependence was also found in the flow velocity measurements. CONCLUSION: Our results demonstrated the feasibility of using FC and NC dMRI to noninvasively measure ballistic flow velocity in the placenta, which may be used as a new marker to evaluate placenta microcirculation.

Fetal brain tissue characterization at 1.5 T using STrategically Acquired Gradient Echo (STAGE) imaging.

OBJECTIVES: To estimate human fetal brain MRI tissue properties including apparent T1 (T1app) and apparent proton density (PDapp) by using a rapid multi-contrast acquisition protocol called STrategically Acquired Gradient Echo (STAGE) imaging. METHODS: STAGE data were collected using two flip angles (15° and 60°, with a TR = 600 ms) for 30 pregnant women at 1.5 T (15 healthy controls: gestational age (GA) range 19 + 1/7 weeks to 34 + 5/7 weeks; 11 abnormal subjects with ventriculomegaly: GA range 21 + 5/7 weeks to 31 + 5/7 weeks; 4 subjects with other abnormalities). Both T1app and PDapp maps of the fetal brain were calculated from the STAGE data. A region-of-interest-based approach was used to measure T1app and PDapp in the subplate/intermediate zone (SP/IZ), cortical plate (CP), and cerebrospinal fluid (CSF) in the fetal brain. RESULTS: The ratios of T1appSP/IZ/T1appCP and PDappSP/IZ/PDappCP were larger than unity while T1appSP/IZ/T1appCSF and PDappSP/IZ/PDappCSF were both less than unity. CONCLUSIONS: STAGE imaging provides a potential practical approach to estimate multi-parametric properties of the human fetal brain. KEY POINTS: • STAGE is feasible in measuring fetal brain tissue properties. • Water content in cortical plate and subplate/intermediate zone approaches that of cerebrospinal fluid in early gestational ages.

Neonatal outcome in 29 pregnant women with COVID-19: A retrospective study in Wuhan, China.

BACKGROUND: As of June 1, 2020, coronavirus disease 2019 (COVID-19) has caused more than 6,000,000 infected persons and 360,000 deaths globally. Previous studies revealed pregnant women with COVID-19 had similar clinical manifestations to nonpregnant women. However, little is known about the outcome of neonates born to infected women. METHODS AND FINDINGS: In this retrospective study, we studied 29 pregnant women with COVID-19 infection delivered in 2 designated general hospitals in Wuhan, China between January 30 and March 10, 2020, and 30 neonates (1 set of twins). Maternal demographic characteristics, delivery course, symptoms, and laboratory tests from hospital records were extracted. Neonates were hospitalized if they had symptoms (5 cases) or their guardians agreed to a hospitalized quarantine (13 cases), whereas symptom-free neonates also could be discharged after birth and followed up through telephone (12 cases). For hospitalized neonates, laboratory test results and chest X-ray or computed tomography (CT) were extracted from hospital records. The presence of antibody of SARS-CoV-2 was assessed in the serum of 4 neonates. Among 29 pregnant COVID-19-infected women (13 confirmed and 16 clinical diagnosed), the majority had higher education (56.6%), half were employed (51.7%), and their mean age was 29 years. Fourteen women experienced mild symptoms including fever (8), cough (9), shortness of breath (3), diarrhea (2), vomiting (1), and 15 were symptom-free. Eleven of 29 women had pregnancy complications, and 27 elected to have a cesarean section delivery. Of 30 neonates, 18 were admitted to Wuhan Children's Hospital for quarantine and care, whereas the other 12 neonates discharged after birth without any symptoms and had normal follow-up. Five hospitalized neonates were diagnosed as COVID-19 infection (2 confirmed and 3 suspected). In addition, 12 of 13 other hospitalized neonates presented with radiological features for pneumonia through X-ray or CT screening, 1 with occasional cough and the others without associated symptoms. SARS-CoV-2 specific serum immunoglobulin M (IgM) and immunoglobulin G (IgG) were measured in 4 neonates and 2 were positive. The limited sample size limited statistical comparison between groups. CONCLUSIONS: In this study, we observed COVID-19 or radiological features of pneumonia in some, but not all, neonates born to women with COVID-19 infection. These findings suggest that intrauterine or intrapartum transmission is possible and warrants clinical caution and further investigation. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2000031954 (Maternal and Perinatal Outcomes of Women with coronavirus disease 2019 (COVID-19): a multicenter retrospective cohort study).

Chromosomal microarray analysis in fetuses with congenital anomalies of the kidney and urinary tract: A prospective cohort study and meta-analysis.

OBJECTIVE: To evaluate the usefulness and incremental diagnostic yield of chromosomal microarray analysis (CMA) compared with standard karyotyping in fetuses with congenital anomalies of the kidney and urinary tract (CAKUT). METHODS: A prospective cohort study and systematic review of the literature were conducted. In the prospective cohort study, 123 fetuses with CAKUT, as detected by prenatal ultrasound at our center, were enrolled and evaluated using karyotyping and CMA. In the meta-analysis, articles in PubMed and ISI Web of Knowledge databases describing copy number variations (CNVs) in prenatal cases of CAKUT were included. RESULTS: Among the 123 fetuses in our prospective cohort study, 13 fetuses were detected with chromosomal abnormalities or submicroscopic chromosomal abnormalities by both karyotyping and CMA. In the remaining 110 fetuses, four pathogenic CNVs in four fetuses were only detected by CMA, indicating an excess diagnostic yield of 3.6%. Six publications and our own study met the inclusion criteria for the meta-analysis. In total, 615 fetuses with CAKUT were included. The pooled data from all of the reviewed studies indicate that the incremental yield of CMA over karyotyping was 3.8%. CONCLUSION: The use of CMA provides a 3.8% incremental yield of detecting pathogenic CNVs in fetuses with CAKUT and normal karyotype.

An unusual cause of postmenopausal vaginal haemorrhage: a case report.

BACKGROUND: Post-menopause vaginal haemorrhage is typically related to gynaecological malignancies. Bleeding from vaginal varices rarely occurs, especially in nonpregnant women. Moreover, nonpregnancy-related causes of vaginal varicosities include portal hypertension, especially that caused by liver cirrhosis, pelvic congestion syndrome and Klippel-Trenaunay syndrome or Parkes-Weber syndrome. Here, we report an unusual cause of nonpregnancy-associated vaginal variceal bleeding. CASE PRESENTATION: A 55-year-old postmenopausal woman presented in our outpatient department with complaints of recurrent bloody vaginal discharge. A group of varicose veins and several haemorrhagic spots were found on her vaginal wall during a vaginal speculum examination. Genital cancers were excluded by colposcopy and transvaginal ultrasonography; furthermore, a pelvic arteriovenous fistula was not found on a pelvic computed tomography (CT) scan. However, congenital varicosities and deep arteriovenous shunts were observed in her left leg on arterial angiography. Moreover, vaginal bleeding was improved after resolution of the underlying deep arteriovenous shunts in her left leg. Therefore, congenital arteriovenous shunts and elevated inferior vena cava pressure might be responsible for her recurrent vaginal varicose bleeding. CONCLUSION: Haemorrhage due to vaginal varices is easily detected with a vaginal speculum examination. However, diagnosis and treatment of the original disease are important after bleeding is controlled.

Comparison of the value of superficial mark guided localization and hook-wire guided localization techniques for non-palpable breast microcalcifications: A retrospective clinical research.

AIM: The present study compares the effect and accuracy of the superficial mark guided localization (SGL) and hook-wire guided localization (WGL) techniques for non-palpable breast microcalcifications. METHODS: This retrospective study was conducted to compare SGL and WGL techniques. These techniques were performed on 51 patients with non-palpable breast microcalcifications from January 2015 to May 2016. RESULTS: Among these 51 patients, 25 (49.01%) patients were subjected to WGL and 26 patients (50.99%) were subjected to SGL. The SGL technique had a higher rate of malignant cancer detection (WGL = 12.0% and SGL = 23.0%). Furthermore, no significant differences were found with regard to average age, the rate of a second excision and the diameter of the excised tissue. Moreover, no complications were observed in the SGL group, while four (16.0%) patients in the WGL group experienced problems. CONCLUSION: The SGL technique is as accurate as the WGL technique. Furthermore, the procedure has advantages of being less expensive and causing less complications.

Hemoglobin ßCys93 is essential for cardiovascular function and integrated response to hypoxia.

Oxygen delivery by Hb is essential for vertebrate life. Three amino acids in Hb are strictly conserved in all mammals and birds, but only two of those, a His and a Phe that stabilize the heme moiety, are needed to carry O2. The third conserved residue is a Cys within the ß-chain (ßCys93) that has been assigned a role in S-nitrosothiol (SNO)-based hypoxic vasodilation by RBCs. Under this model, the delivery of SNO-based NO bioactivity by Hb redefines the respiratory cycle as a triune system (NO/O2/CO2). However, the physiological ramifications of RBC-mediated vasodilation are unknown, and the apparently essential nature of ßCys93 remains unclear. Here we report that mice with a ßCys93Ala mutation are deficient in hypoxic vasodilation that governs blood flow autoregulation, the classic physiological mechanism that controls tissue oxygenation but whose molecular basis has been a longstanding mystery. Peripheral blood flow and tissue oxygenation are decreased at baseline in mutant animals and decline excessively during hypoxia. In addition, ßCys93Ala mutation results in myocardial ischemia under basal normoxic conditions and in acute cardiac decompensation and enhanced mortality during transient hypoxia. Fetal viability is diminished also. Thus, ßCys93-derived SNO bioactivity is essential for tissue oxygenation by RBCs within the respiratory cycle that is required for both normal cardiovascular function and circulatory adaptation to hypoxia.

Reversibly Reconfigurable Colloidal Plasmonic Nanomaterials.

With their unique ability to concentrate and scatter light, plasmonic nanomaterials have been the focus of tremendous synthesis and characterization efforts in the past two decades. Recently, the topic of reversibly reconfigurable plasmonic nanomaterials has become an intensive research area offering the opportunity to reconfigure the optical, mechanical, electronic, and catalytic properties of materials with promising applications in fields ranging from biosensors to nanorobotics and energy. This Perspective discusses the state of the art in the fabrication and application of reversibly reconfigurable colloidal plasmonic nanomaterials based on the actuation of interparticle couplings and explores some promising directions for future research ranging from direction control, two-dimensional materials, and the incorporation of feedback mechanisms for designing robust responses.

Controlling Association and Separation of Gold Nanoparticles with Computationally Designed Zinc-Coordinating Proteins.

Functionalization of nanoparticles with biopolymers has yielded a wide range of structured and responsive hybrid materials. DNA provides the ability to program length and recognition using complementary oligonucleotide sequences. Nature more often leverages the versatility of proteins, however, where structure, assembly, and recognition are more subtle to engineer. Herein, a protein was computationally designed to present multiple Zn2+ coordination sites and cooperatively self-associate to form an antiparallel helical homodimer. Each subunit was unstructured in the absence of Zn2+ or when the cation was sequestered with a chelating agent. When bound to the surface of gold nanoparticles via cysteine, the protein provided a reversible molecular linkage between particles. Nanoparticle association and changes in interparticle separation were monitored by redshifts in the surface plasmon resonance (SPR) band and by transmission electron microscopy (TEM). Titrations with Zn2+ revealed sigmoidal transitions at submicromolar concentrations. The metal-ion concentration required to trigger association varied with the loading of the proteins on the nanoparticles, the solution ionic strength, and the cation employed. Specifying the number of helical (heptad) repeat units conferred control over protein length and nanoparticle separation. Two different length proteins were designed via extension of the helical structure. TEM and extinction measurements revealed distributions of nanoparticle separations consistent with the expected protein structures. Nanoparticle association, interparticle separation, and SPR properties can be tuned using computationally designed proteins, where protein structure, folding, length, and response to molecular species such as Zn2+ can be engineered.

Forkhead box protein k1 recruits TET1 to act as a tumor suppressor and is associated with MRI detection.

OBJECTIVE: Today, more and more evidence suggests that Foxk proteins (Foxk1 and Foxk2) work as transcriptional repressors in different kinds of cancer, but whether Foxk1 has a role in mediating tumorigenesis in breast cancer, the evidence is rare. METHODS: MCF-7 cells transfected with shFoxk1 displayed a mesenchymal morphology and reduced the expression of E-cadherin, and increased the expression of N-cadherin. Transwell invasion assay and living imaging assay show that the overexpression of Foxk1 could inhibit metastasis in vitro and in vivo. Ribonucleic acid sequencing revealed that the knockdown of Foxk1 resulted in the up-regulation of different oncogenes, which was implicated in metastasis and tumor angiopoiesis. Quantitative chromatin immunoprecipitation, chromatin immunoprecipitation and Luciferase reporter assays suggested that Foxk1 could bind to the promoter of epithelial-mesenchymal transition inducer Twist and vascular endothelial growth factor, VEGF. Mass Spectrometry, co-immunoprecipitation assays and glutathione-S-transferase pull-down assay detected that Foxk1 was physically associated with Ten-eleven translocation 1, TET1, in vivo and in vitro. RESULTS: We reported that the mean expression level of Foxk1 in breast cancer was significantly lower than the adjacent noncarcinoma tissue. The higher Foxk1 expression was associated with better prognosis. Endothelial tube formation assays indicated that Foxk1 might regulate breast cancer angiogenesis through transcriptional repression of vascular endothelial growth factor. Furthermore, in vivo magnetic resonance imaging revealed the overexpression of Foxk1 could enhance the detection of the tumors. Further, a strong negative correlation was observed between Foxk1 and Twsit or between Foxk1 and vascular endothelial growth factor, and the higher Foxk1 expression is correlated with better over all survivals and better relapse-free survivals. CONCLUSIONS: Together, our data indicated the function of Foxk1 as a tumor suppressor in facilitating angiogenesis and metastasis in breast cancer.