Conformational changes during pore formation by the perforin-related protein pleurotolysin

Membrane attack complex/perforin-like (MACPF) proteins comprise the largest superfamily of pore-forming proteins, playing crucial roles in immunity and pathogenesis. Soluble monomers assemble into large transmembrane pores via conformational transitions that remain to be structurally and mechanistically characterised. Here we present an 11 Å resolution cryo-electron microscopy (cryo-EM) structure of the two-part, fungal toxin Pleurotolysin (Ply), together with crystal structures of both components (the lipid binding PlyA protein and the pore-forming MACPF component PlyB). These data reveal a 13-fold pore 80 Å in diameter and 100 Å in height, with each subunit comprised of a PlyB molecule atop a membrane bound dimer of PlyA. The resolution of the EM map, together with biophysical and computational experiments, allowed confident assignment of subdomains in a MACPF pore assembly. The major conformational changes in PlyB are a ~70° opening of the bent and distorted central β-sheet of the MACPF domain, accompanied by extrusion and refolding of two α-helical regions into transmembrane β-hairpins (TMH1 and TMH2). We determined the structures of three different disulphide bond-trapped prepore intermediates. Analysis of these data by molecular modelling and flexible fitting allows us to generate a potential trajectory of β-sheet unbending. The results suggest that MACPF conformational change is triggered through disruption of the interface between a conserved helix-turn-helix motif and the top of TMH2. Following their release we propose that the transmembrane regions assemble into β-hairpins via top down zippering of backbone hydrogen bonds to form the membrane-inserted β-barrel. The intermediate structures of the MACPF domain during refolding into the β-barrel pore establish a structural paradigm for the transition from soluble monomer to pore, which may be conserved across the whole superfamily. The TMH2 region is critical for the release of both TMH clusters, suggesting why this region is targeted by endogenous inhibitors of MACPF function

Molar pregnancy and childhood cancer: a population-based linkage study from Denmark

We observed a relative risk of 1.40 (95% confidence interval; 0.86–2.16) for cancers diagnosed under the age 20 in 6192 offspring of 3431 mothers with a molar pregnancy, indicating it is not a major determinant of childhood cancer

Grisel\u2019s syndrome: Non-traumatic atlantoaxial rotatory subluxation\u2014report of five cases and review of the literature

Background: In children, when unresponsive neck rigidity and distress are observed after ear, nose and throat (ENT) surgical treatment or nasopharyngeal inflammation, Grisel\u2019s syndrome should be suspected. This is a rare syndrome involving non-traumatic rotatory subluxation of the atlantoaxial joint. Conservative management with external cervical orthoses and empirical antibiotic, muscle relaxant and analgesic therapy should be the first choice of treatment. Surgical stabilization is indicated when high-grade instability or failure of stable reduction are observed. The instability is graded according to the classification system devised by Fielding and Hawkins. Several recommendations for treatment are available in the literature, but there are no common guidelines. In this paper, the authors discuss the need for prompt diagnosis and treatment considerations. Case Description: Five children with Fielding type I\u2013III rotatory subluxation are reported. Three patients were treated with a cervical collar, and one patient was treated with skull traction and sternal\u2013occipital\u2013mandibular immobilizer (SOMI) brace application. Surgical treatment was necessary for one patient after failure of initial conservative management. The intervals between the onset of torticollis and radiological diagnosis ranged from 12 to 90 days. A relationship between an increased grade of instability and delayed diagnosis was observed. Conclusion: In children with painful torticollis following ENT procedures or nasopharyngeal inflammation, Grisel\u2019s syndrome should always be suspected. Cervical magnetic resonance imaging (MRI) allows prompt and safe diagnosis, and a three-dimensional computed tomography (CT) scan provides better classification of the instability. Surgery, which is indicated in cases of high-grade instability or failure of conservative treatment, may be avoided with prompt diagnosis

Social Responsibility as a Factor of Convergence in Corporate Governance

For a long time, the corporate governance decisions and the connected disclosure activities were often direct to the satisfaction of shareholders’ expectations, sometimes with significant differences related to the characteristics of the stock markets and the composition of the corporate ownership. In the listed companies, this management orientation tended to generate divergences between insider and outsider corporate governance systems. The emergence of the concepts of corporate social responsibility (CSR) and Stakeholder Relations Management involves modifications in the corporate governance approach, according with the philosophy of sustainable development as critical element for long-term success in global markets. This chapter aims to make some considerations when the CSR adoption and disclosure as element characterizing corporate culture represent a factor of convergence between insider and outsider corporate governance systems