Newcastle disease virus HN protein alters the conformation of the F protein at cell surfaces

Conformational changes in the Newcastle disease virus (NDV) fusion (F) protein during activation of fusion and the role of HN protein in these changes were characterized with a polyclonal antibody. This antibody was raised against a peptide with the sequence of the amino-terminal half of the F protein HR1 domain. This antibody immunoprecipitated both F(0) and F(1) forms of the fusion protein from infected and transfected cell extracts solubilized with detergent, and precipitation was unaffected by expression of the HN protein. In marked contrast, this antibody detected significant conformational differences in the F protein at cell surfaces, differences that depended upon HN protein expression. The antibody minimally detected the F protein, either cleaved or uncleaved, in the absence of HN protein expression. However, when coexpressed with HN protein, an uncleaved mutant F protein bound the anti-HR1 antibody, and this binding depended upon the coexpression of specifically the NDV HN protein. When the cleaved wild-type F protein was coexpressed with HN protein, the F protein bound anti-HR1 antibody poorly although significantly more than F protein expressed alone. Anti-HR1 antibody inhibited the fusion of R18 (octadecyl rhodamine B chloride)-labeled red blood cells to syncytia expressing HN and wild-type F proteins. This inhibition showed that fusion-competent F proteins present on surfaces of syncytia were capable of binding anti-HR1. Furthermore, only antibody which was added prior to red blood cell binding could inhibit fusion. These results suggest that the conformation of uncleaved cell surface F protein is affected by HN protein expression. Furthermore, the cleaved F protein, when coexpressed with HN protein and in a prefusion conformation, can bind anti-HR1 antibody, and the anti-HR1-accessible conformation exists prior to HN protein attachment to receptors on red blood cells.     

Thiol-bearing synthetic peptides retain the antioxidant activity of apolipoproteinA-I(Milano)

Apolipoprotein(apo)A-I(Milano) (R173C) and apoA-I(Paris) (R151C) are rare cysteine variants of wild-type (WT) apoA-I that possess novel antioxidant properties on phospholipid surfaces. Yet, the two variants differ in their ability to inhibit lipid peroxidation. In this study, we used synthetic peptides (18mers) to investigate the structural basis for the difference in antioxidant activity between apoA-I(Milano) and apoA-I(Paris). A peptide (aa 167-R173C-184) based on the amphipathic alpha helix harboring the R173C mutation inhibited superoxide anion-mediated oxidation of phospholipid in a dose-dependent manner, but it failed to directly quench superoxide anions in aqueous solution, indicating that the peptide acted at the level of phospholipid to inhibit lipid peroxidation just like the full-length cysteine variant. Peptide 145-R151C-162 based on the helical segment containing R151C exhibited the same capacity as peptide 167-R173C-184 to inhibit lipid peroxidation. Thus, the difference in antioxidant activity between apoA-I(Milano) and apoA-I(Paris) was not governed by the primary amino acid sequence of their individual amphipathic alpha helices, rather contextual constraints within the full-length variants set the difference in antioxidant activity. Cysteine-free peptides were weak inhibitors of lipid peroxidation. These results suggest that thiol-bearing helical peptides based on apoA-I(Milano) may be useful to combat inflammatory related diseases.     

Feasibility and Preliminary Efficacy of Visual Cue Training to Improve Adaptability of Walking after Stroke: Multi-Centre,Single-Blind Randomised Control Pilot Trial

Objectives

Given the importance of vision in the control of walking and evidence indicating varied practice of walking improves mobility outcomes, this study sought to examine the feasibility and preliminary efficacy of varied walking practice in response to visual cues, for the rehabilitation of walking following stroke.

Design

This 3 arm parallel, multi-centre, assessor blind, randomised control trial was conducted within outpatient neurorehabilitation services

Participants

Community dwelling stroke survivors with walking speed <0.8m/s, lower limb paresis and no severe visual impairments

Intervention

Over-ground visual cue training (O-VCT), Treadmill based visual cue training (T-VCT), and Usual care (UC) delivered by physiotherapists twice weekly for 8 weeks.Main outcome measures: Participants were randomised using computer generated random permutated balanced blocks of randomly varying size. Recruitment, retention, adherence, adverse events and mobility and balance were measured before randomisation, post-intervention and at four weeks follow-up.

Results

Fifty-six participants participated (18 T-VCT, 19 O-VCT, 19 UC). Thirty-four completed treatment and follow-up assessments. Of the participants that completed, adherence was good with 16 treatments provided over (median of) 8.4, 7.5 and 9 weeks for T-VCT, O-VCT and UC respectively. No adverse events were reported. Post-treatment improvements in walking speed, symmetry, balance and functional mobility were seen in all treatment arms.

Conclusions

Outpatient based treadmill and over-ground walking adaptability practice using visual cues are feasible and may improve mobility and balance. Future studies should continue a carefully phased approach using identified methods to improve retention.

Trial Registration

Clinicaltrials.gov NCT01600391     

Intrapopulation Genome Size Variation in D. melanogaster Reflects Life History Variation and Plasticity

We determined female genome sizes using flow cytometry for 211 Drosophila melanogaster sequenced inbred strains from the Drosophila Genetic Reference Panel, and found significant conspecific and intrapopulation variation in genome size. We also compared several life history traits for 25 lines with large and 25 lines with small genomes in three thermal environments, and found that genome size as well as genome size by temperature interactions significantly correlated with survival to pupation and adulthood, time to pupation, female pupal mass, and female eclosion rates. Genome size accounted for up to 23% of the variation in developmental phenotypes, but the contribution of genome size to variation in life history traits was plastic and varied according to the thermal environment. Expression data implicate differences in metabolism that correspond to genome size variation. These results indicate that significant genome size variation exists within D. melanogaster and this variation may impact the evolutionary ecology of the species. Genome size variation accounts for a significant portion of life history variation in an environmentally dependent manner, suggesting that potential fitness effects associated with genome size variation also depend on environmental conditions.     

A Recessive Founder Mutation in Regulator of Telomere Elongation Helicase 1, RTEL1, Underlies Severe Immunodeficiency and Features of Hoyeraal Hreidarsson Syndrome

Dyskeratosis congenita (DC) is a heterogeneous inherited bone marrow failure and cancer predisposition syndrome in which germline mutations in telomere biology genes account for approximately one-half of known families. Hoyeraal Hreidarsson syndrome (HH) is a clinically severe variant of DC in which patients also have cerebellar hypoplasia and may present with severe immunodeficiency and enteropathy. We discovered a germline autosomal recessive mutation in RTEL1, a helicase with critical telomeric functions, in two unrelated families of Ashkenazi Jewish (AJ) ancestry. The affected individuals in these families are homozygous for the same mutation, R1264H, which affects three isoforms of RTEL1. Each parent was a heterozygous carrier of one mutant allele. Patient-derived cell lines revealed evidence of telomere dysfunction, including significantly decreased telomere length, telomere length heterogeneity, and the presence of extra-chromosomal circular telomeric DNA. In addition, RTEL1 mutant cells exhibited enhanced sensitivity to the interstrand cross-linking agent mitomycin C. The molecular data and the patterns of inheritance are consistent with a hypomorphic mutation in RTEL1 as the underlying basis of the clinical and cellular phenotypes. This study further implicates RTEL1 in the etiology of DC/HH and immunodeficiency, and identifies the first known homozygous autosomal recessive disease-associated mutation in RTEL1.