Structure of the reovirus outer capsid and dsRNA-binding protein σ3 at 1.8 Å resolution

The crystallographically determined structure of the reovirus outer capsid protein σ3 reveals a two-lobed structure organized around a long central helix. The smaller of the two lobes includes a CCHC zinc-binding site. Residues that vary between strains and serotypes lie mainly on one surface of the protein; residues on the opposite surface are conserved. From a fit of this model to a reconstruction of the whole virion from electron cryomicroscopy, we propose that each σ3 subunit is positioned with the small lobe anchoring it to the protein µ1 on the surface of the virion, and the large lobe, the site of initial cleavages during entry-related proteolytic disassembly, protruding outwards. The surface containing variable residues faces solvent. The crystallographic asymmetric unit contains two σ3 subunits, tightly associated as a dimer. One broad surface of the dimer has a positively charged surface patch, which extends across the dyad. In infected cells, σ3 binds dsRNA and inhibits the interferon response. The location and extent of the positively charged surface patch suggest that the dimer is the RNA-binding form of σ3

Patients Treated for Central Airway Stenosis After Lung Transplantation Have Persistent Airflow Limitation

BACKGROUND: Although central airway stenosis (CAS) is a common complication after lung transplantation, its consequences have been poorly evaluated. The objective of our study was to evaluate the impact of CAS on lung function after lung transplantation. MATERIAL AND METHODS: All lung transplant recipients from June 2009 to August 2014 in a single center (Strasbourg, France) were retrospectively reviewed. RESULTS: A total of 191 lung transplantations were performed: 175 bilateral, 15 single, and 1 heart-lung transplantation. Of the 161 bilateral lung-transplanted patients who survived >3 months, 22 (13.6%) developed CAS requiring endobronchial treatment. All these patients were treated by endoscopic balloon dilatation, and 9 additionally needed endobronchial stents. Respiratory function tests demonstrated persistent obstructive ventilatory pattern despite endoscopic treatment in recipients with CAS compared to those without CAS at 6, 12, and 18 months post-transplant. At 18 months, CAS patients had significantly lower post-transplant FEV1 (1.96±0.60 L versus 2.57±0.76 L, p=0.001) and FEV1/FVC (61±14% versus 81±13%, p<0.001). The percentage of patients hospitalized for respiratory infections and number of hospital days were significantly increased in recipients with CAS (20 [91%] versus 92 [66%] p=0.036, and 144±110 days versus 103±83 days p=0.042, respectively). Survival in transplant recipients did not significantly differ between those with CAS and those without. CONCLUSIONS: CAS after lung transplantation was not associated with worse survival, but it did have a significant and persistent effect on lung function, and was associated with increased rate of respiratory infection

Triad of polar residues implicated in pH specificity of acidic mammalian chitinase

Acidic mammalian chitinase (AMCase) is a mammalian chitinase that has been implicated in allergic asthma. One of only two active mammalian chinases, AMCase, is distinguished from other chitinases by several unique features. Here, we present the novel structure of the AMCase catalytic domain, both in the apo form and in complex with the inhibitor methylallosamidin, determined to high resolution by X-ray crystallography. These results provide a structural basis for understanding some of the unique characteristics of this enzyme, including the low pH optimum and the preference for the β-anomer of the substrate. A triad of polar residues in the second-shell is found to modulate the highly conserved chitinase active site. As a novel target for asthma therapy, structural details of AMCase activity will help guide the future design of specific and potent AMCase inhibitors

A Molecular Dynamics Study of Reovirus Attachment Protein σ1 Reveals Conformational Changes in σ1 Structure

Molecular dynamics simulations were performed using the recently determined crystal structure of the reovirus attachment protein, σ1. These studies were conducted to improve an understanding of two unique features of σ1 structure: the protonation state of Asp(345), which is buried in the σ1 trimer interface, and the flexibility of the protein at a defined region below the receptor-binding head domain. Three copies of aspartic acids Asp(345) and Asp(346) cluster in a solvent-inaccessible and hydrophobic region at the σ1 trimer interface. These residues are hypothesized to mediate conformational changes in σ1 during viral attachment or cell entry. Our results indicate that protonation of Asp(345) is essential to the integrity of the trimeric structure seen by x-ray crystallography, whereas deprotonation induces structural changes that destabilize the trimer interface. This finding was confirmed by electrostatic calculations using the finite difference Poisson-Boltzmann method. Earlier studies show that σ1 can exist in retracted and extended conformations on the viral surface. Since protonated Asp(345) is necessary to form a stable, extended trimer, our results suggest that protonation of Asp(345) may allow for a structural transition from a partially detrimerized molecule to the fully formed trimer seen in the crystal structure. Additional studies were conducted to quantify the previously observed flexibility of σ1 at a defined region below the receptor-binding head domain. Increased mobility was observed for three polar residues (Ser(291), Thr(292), and Ser(293)) located within an insertion between the second and third β-spiral repeats of the crystallized portion of the σ1 tail. These amino acids interact with water molecules of the solvent bulk and are responsible for oscillating movement of the head of ∼50° during 5 ns of simulations. This flexibility may facilitate viral attachment and also function in cell entry and disassembly. These findings provide new insights about the conformational dynamics of σ1 that likely underlie the initiation of the reovirus infectious cycle

Thymomectomy plus total thymectomy versus simple thymomectomy for early-stage thymoma without myasthenia gravis : a European Society of Thoracic Surgeons Thymic Working Group Study

OBJECTIVES: Resection of thymic tumours including the removal of both the tumour and the thymus gland (thymothymectomy; TT) is the procedure of choice and is recommended in most relevant articles in the literature. Nevertheless, in recent years, some authors have suggested that resection of the tumour (simple thymomectomy; ST) may suffice from an oncological standpoint in patients with early-stage thymoma who do not have myasthenia gravis (MG) (non-MG). The goal of our study was to compare the short- and long-term outcomes of ST versus TT in non-MG early-stage thymomas using the European Society of Thoracic Surgeons thymic database.METHODS: A total of 498 non-MG patients with pathological stage I thymoma were included in the study. TT was performed in 466 (93.6%) of 498 patients who had surgery with curative intent; ST was done in 32 (6.4%). The completeness of resection, the rate of complications, the 30-day mortality, the overall recurrence and the freedom from recurrence were compared. We performed crude and propensity score-adjusted comparisons by surgical approach (ST vs TT).RESULTS: TT showed the same rate of postoperative complications, 30-day mortality and postoperative length of stay as ST. The 5-year overall survival rate was 89% in the TT group and 55% in the ST group. The 5-year freedom from recurrence was 96% in the TT group and 79% in the ST group.CONCLUSION: Patients with early-stage thymoma without MG who have a TT show significantly better freedom from recurrence than those who have an ST, without an increase in postoperative morbidity rate