Crystallization, structural diversity and anisotropy effects in 2D arrays of icosahedral viruses.

We investigate two-dimensional (2D) assembly of the icosahedral turnip yellow mosaic virus (TYMV) under cationic lipid monolayers at the aqueous solution­vapor interface. The 2D crystallization of TYMV has been achieved by enhancing electrostatically induced interfacial adsorption, an approach recently demonstrated for another virus. In situ X-ray scattering reveals two close-packed 2D crystalline phases of TYMV that are distinct from the previously reported hexagonal and centered square (√2 × âˆš2) arrays of TYMV. One of the newly observed phases arises from either a dimeric double-square (2 × 1) or tetrameric square (2 × 2) unit cell. The other is a rhombic crystal with a lattice angle of 80°. The two observed crystal phases are substantially less dense (by over 10%) than a 2D lattice of TYMV could be according to its known size and shape, indicating that local anisotropic interparticle interactions play a key role in stabilizing these crystals. TYMV's anisotropy attributes and numerical analysis of 2D arrays of virus-shaped particles are used to derive a model for the rhombic crystal in which the particle orientation is consistent with the electrostatic lipid­TYMV attraction and the interparticle contacts exhibit steric complementarity. The interplay between particle anisotropy and packing is contrasted between the rhombic crystal model and the square (√2 × âˆš2) crystal. This study highlights how the high symmetry and subtle asphericity of icosahedral particles enrich the variety and complexity of ordered 2D structures that can be generated through self-assembly.

Multivalent ligand displayed on plant virus induces rapid onset of bone differentiation.

Viruses are monodispersed biomacromolecules with well-defined 3-D structures at the nanometer level. The relative ease to manipulate viral coat protein gene to display numerous functional groups affords an attractive feature for these nanomaterials, and the inability of plant viruses to infect mammalian hosts poses little or no cytotoxic concerns. As such, these nanosized molecular tools serve as powerful templates for many pharmacological applications ranging as multifunctional theranostic agents with tissue targeting motifs and imaging agents, potent vaccine scaffolds to induce cellular immunity and for probing cellular functions as synthetic biomaterials. The results herein show that combination of serum-free, chemically defined media with genetically modified plant virus induces rapid onset of key bone differentiation markers for bone marrow derived mesenchymal stem cells within two days. The xeno-free culture is often a key step toward development of ex vivo implants, and the early onset of osteocalcin, BMP-2 and calcium sequestration are some of the key molecular markers in the progression toward bone formation. The results herein will provide some key insights to engineering functional materials for rapid bone repair.

Porous alginate hydrogel functionalized with virus as three-dimensional scaffolds for bone differentiation.

In regenerative medicine, a synthetic extracellular matrix is crucial for supporting stem cells during its differentiation process to integrate into surrounding tissues. Hydrogels are used extensively in biomaterials as synthetic matrices to support the cells. However, to mimic the biological niche of a functional tissue, various chemical functionalities are necessary. We present here, a method of functionalizing a highly porous hydrogel with functional groups by mixing the hydrogel with a plant virus, tobacco mosaic virus (TMV), and its mutant. The implication of this process resides with the three important features of TMV: its well-defined genetic/chemical modularity, its multivalency (TMV capsid is composed of 2130 copies of identical subunits), and its well-defined structural features. Previous studies utilizing the native TMV on two-dimensional supports accelerated mesenchymal stem cell differentiation, and surfaces modified with genetically modified viral particles further enhanced cell attachment and differentiation. Herein we demonstrate that functionalization of a porous alginate scaffold can be achieved by the addition of viral particles with minimal processing and downstream purifications, and the cell attachment and differentiation within the macroporous scaffold can be effectively manipulated by altering the peptide or small molecule displayed on the viral particles.

Mutant plant viruses with cell binding motifs provide differential adhesion strengths and morphologies.

The ability of Tobacco mosaic virus (TMV) to tolerate various amino acid insertions near its carboxy terminus is well-known. Typically these inserts are based on antigenic sequences for vaccine development with plant viruses as carriers. However, we determined that the structural symmetries and the size range of the viruses could also be modeled to mimic the extracellular matrix proteins by inserting cell-binding sequences to the virus coat protein. The extracellular matrix proteins play important roles in guiding cell adhesion, migration, proliferation, and stem cell differentiation. Previous studies with TMV demonstrated that the native and phosphate-modified virus particles enhanced stem cell differentiation toward bone-like tissues. Based on these studies, we sought to design and screen multiple genetically modified TMV mutants with reported cell adhesion sequences to expand the virus-based tools for cell studies. Here, we report the design of these mutants with cell binding amino acid motifs derived from several proteins, the stabilities of the mutants against proteases during purification and storage, and a simple and rapid functional assay to quantitatively determine adhesion strengths by centrifugal adhesion assay. Among the mutants, we found that cells on TMV expressing RGD motifs formed filopodial extensions with weaker attachment profiles, whereas the cells on TMV expressing collagen I mimetic sequence displayed little spreading but higher attachment strengths.

Evaluation of Patients with Heart Failure to Determine Eligibility for Treatment with Sacubitril/Valsartan: Insights from a Veterans Administration Healthcare System.

STUDY OBJECTIVE: Despite evidence that supports the use of sacubitril/valsartan - the first angiotensin II receptor blocker-neprilysin inhibitor - for mortality reduction in patients with heart failure (HF), it remains underprescribed. The objective of this study was to evaluate eligibility for initiation of sacubitril/valsartan treatment in patients with HF within the largest Veterans Administration healthcare system in the United States. DESIGN: Cross-sectional study. SETTING: Veterans Affairs Greater Los Angeles Healthcare System (VAGLAHS). PATIENTS: A total of 2985 patients with a HF diagnosis who were alive as of November 1, 2017. MEASUREMENTS AND MAIN RESULTS: Eligibility for sacubitril/valsartan initiation was based on inclusion and exclusion criteria from the Prospective Comparison of Angiotensin Receptor-Neprilysin Inhibitor with Angiotensin-Converting-Enzyme Inhibitor to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) trial and the VA Criteria for Use. The proportion of eligible patients was estimated, and characteristics of eligible patients were compared with those in the PARADIGM-HF trial. Of the 2985 patients with HF who were alive as of November 1, 2017, 965 (32.3%) had HF with reduced ejection fraction (HFrEF). Of these patients with HFrEF, 263 (27.3%) fulfilled eligibility criteria and were considered candidates for sacubitril/valsartan initiation. Of the 702 patients who did not fulfil eligibility criteria, the most common reasons were New York Heart Association functional class I (35.3%) and B-type natriuretic peptide level of 100 pg/ml or lower (22.2%). Compared with patients in the PARADIGM-HF trial, VAGLAHS patients were older (70.4 vs 63.8 yrs) and more likely to be male (98.5% vs 79.0%), and a higher proportion had New York Heart Association functional class III symptoms (35.4% vs 23.1%). Of the 965 patients with HFrEF, 34 (3.5%) had an active sacubitril/valsartan prescription as of November 1, 2017, of whom 27 (79.4%) did not meet criteria. CONCLUSION: Whereas 27% of patients with HFrEF were eligible to initiate sacubitril/valsartan, only 3.5% of these patients were prescribed the medication. Although sacubitril/valsartan reduced morbidity and mortality in clinical trials, it remains underused within this VA healthcare system. This analysis provides important insights into the VA and other healthcare systems regarding the opportunity for optimizing guideline-directed HF therapy.

Alterations in platelet bioenergetics in Group 2 PH-HFpEF patients.

BACKGROUND: Pulmonary hypertension (PH) is characterized by elevated pulmonary artery pressure but classified into subgroups based on disease etiology. It is established that systemic bioenergetic dysfunction contributes to the pathogenesis of pulmonary arterial hypertension classified as World Health Organization (WHO) Group 1. Consistent with this, we previously showed that platelets from Group 1 PH patients demonstrate increased glycolysis and enhanced maximal capacity for oxidative phosphorylation, which is due to increased fatty acid oxidation (FAO). However, it remains unclear whether identical mitochondrial alterations contribute to the pathology of other PH subgroups. The most prevalent subgroup of PH is WHO Group 2, which encompasses pulmonary venous hypertension secondary to left heart disease. Here, we hypothesized that platelets from Group 2 subjects show bioenergetic alteration compared to controls, and that these changes were similar to Group 1 PH patients. METHOD AND RESULTS: We isolated platelets from subjects with Group 2 PH and controls (n = 20) and measured platelet bioenergetics as well as hemodynamic parameters. We demonstrate that Group 2 PH platelets do not show a change in glycolytic rate but do demonstrate enhanced maximal capacity of respiration due at least partially to increased FAO. Moreover, this enhanced maximal capacity correlates negatively with right ventricular stroke work index and is not changed by administration of inhaled nitrite, a modulator of pulmonary hemodynamics. CONCLUSIONS: These data demonstrate that Group 2 PH subjects have altered bioenergetic function though this alteration is not identical to that of Group 1 PH. The implications of this alteration for disease pathogenesis will be discussed.

Platelets from pulmonary hypertension patients show increased mitochondrial reserve capacity.

Accumulating evidence suggests that altered cellular metabolism is systemic in pulmonary hypertension (PH) and central to disease pathogenesis. However, bioenergetic changes in PH patients and their association with disease severity remain unclear. Here, we hypothesize that alteration in bioenergetic function is present in platelets from PH patients and correlates with clinical parameters of PH. Platelets isolated from controls and PH patients (n = 28) were subjected to extracellular flux analysis to determine oxygen consumption and glycolytic rates. Platelets from PH patients showed greater glycolytic rates than controls. Surprisingly, this was accompanied by significant increases in the maximal capacity for oxygen consumption, leading to enhanced respiratory reserve capacity in PH platelets. This increased platelet reserve capacity correlated with mean pulmonary artery pressure, pulmonary vascular resistance, and right ventricular stroke work index in PH patients and was abolished by the inhibition of fatty acid oxidation (FAO). Consistent with a shift to FAO, PH platelets showed augmented enzymatic activity of carnitine palmitoyltransferase-1 and electron transport chain complex II. These data extend the observation of a metabolic alteration in PH from the pulmonary vascular axis to the hematologic compartment and suggest that measurement of platelet bioenergetics is potentially useful in assessment of disease progression and severity.

Relationship of brain-derived neurotrophic factor and its receptor TrkB to altered inhibitory prefrontal circuitry in schizophrenia.

Dysfunction of inhibitory neurons in the prefrontal cortex (PFC), represented by decreased expression of GABA-related genes such as the 67 kDa isoform of glutamate decarboxylase (GAD67) and parvalbumin (PV), appears to contribute to cognitive deficits in subjects with schizophrenia. We investigated the involvement of signaling mediated by brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase TrkB in producing the altered GABA-related gene expression in schizophrenia. In 15 pairs of subjects with schizophrenia and matched control subjects, both BDNF and TrkB mRNA levels, as assessed by in situ hybridization, were significantly decreased in the PFC of the subjects with schizophrenia, whereas the levels of mRNA encoding the receptor tyrosine kinase for neurotrophin-3, TrkC, were unchanged. In this cohort, within-pair changes in TrkB mRNA levels were significantly correlated with those in both GAD67 and PV mRNA levels. Decreased BDNF, TrkB, and GAD67 mRNA levels were replicated in a second cohort of 12 subject pairs. In the combined cohorts, the correlation between within-pair changes in TrkB and GAD67 mRNA levels was significantly stronger than the correlation between the changes in BDNF and GAD67 mRNA levels. Neither BDNF nor TrkB mRNA levels were changed in the PFC of monkeys after a long-term exposure to haloperidol. Genetically introduced decreases in TrkB expression, but not in BDNF expression, also resulted in decreased GAD67 and PV mRNA levels in the PFC of adult mice; in addition, the cellular pattern of altered GAD67 mRNA expression paralleled that present in schizophrenia. Decreased TrkB signaling appears to underlie the dysfunction of inhibitory neurons in the PFC of subjects with schizophrenia.

Protracted developmental trajectories of GABAA receptor alpha1 and alpha2 subunit expression in primate prefrontal cortex.

BACKGROUND: In schizophrenia, working memory dysfunction is associated with altered expression of gamma-aminobutyric acid (GABA)(A) receptor alpha1 and alpha2 subunits in the dorsolateral prefrontal cortex (DLPFC). In rodents, cortical alpha subunit expression shifts from low alpha1 and high alpha2 to high alpha1 and low alpha2 during early postnatal development. Because these two alpha subunits confer different functional properties to the GABA(A) receptors containing them, we determined whether this shift in alpha1 and alpha2 subunit expression continues through adolescence in the primate DLPFC, potentially contributing to the maturation of working memory during this developmental period. METHODS: Levels of GABA(A) receptor alpha1 and alpha2 subunit mRNAs were determined in the DLPFC of monkeys aged 1 week, 4 weeks, 3 months, 15-17 months (prepubertal), and 43-47 months (postpubertal) and in adult monkeys using in situ hybridization, followed by the quantification of alpha1 subunit protein by western blotting. We also performed whole-cell patch clamp recording of miniature inhibitory postsynaptic potentials (mIPSPs) in DLPFC slices prepared from pre- and postpubertal monkeys. RESULTS: The mRNA and protein levels of alpha1 and alpha2 subunits progressively increased and decreased, respectively, throughout postnatal development including adolescence. Furthermore, as predicted by the different functional properties of alpha1-containing versus alpha2-containing GABA(A) receptors, the mIPSP duration was significantly shorter in postpubertal than in prepubertal animals. CONCLUSIONS: In contrast to rodents, the developmental shift in GABA(A) receptor alpha subunit expression continues through adolescence in primate DLPFC, inducing a marked change in the kinetics of GABA neurotransmission. Disturbances in this shift might underlie impaired working memory in schizophrenia.