Early Onset Prion Disease from Octarepeat Expansion Correlates with Copper Binding Properties

Insertional mutations leading to expansion of the octarepeat domain of the prion protein (PrP) are directly linked to prion disease. While normal PrP has four PHGGGWGQ octapeptide segments in its flexible N-terminal domain, expanded forms may have up to nine additional octapeptide inserts. The type of prion disease segregates with the degree of expansion. With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades. In wild-type PrP, the octarepeat domain takes up copper (Cu2+) and is considered essential for in vivo function. Work from our lab demonstrates that the copper coordination mode depends on the precise ratio of Cu2+ to protein. At low Cu2+ levels, coordination involves histidine side chains from adjacent octarepeats, whereas at high levels each repeat takes up a single copper ion through interactions with the histidine side chain and neighboring backbone amides. Here we use both octarepeat constructs and recombinant PrP to examine how copper coordination modes are influenced by octarepeat expansion. We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts). However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity. We next pooled all published cases of human prion disease resulting from octarepeat expansion and find remarkable agreement between the sudden length-dependent change in copper coordination and onset age. Together, these findings suggest that either loss of PrP copper-dependent function or loss of copper-mediated protection against PrP polymerization makes a significant contribution to early onset prion disease

An Estimate of Avian Mortality at Communication Towers in the United States and Canada

Avian mortality at communication towers in the continental United States and Canada is an issue of pressing conservation concern. Previous estimates of this mortality have been based on limited data and have not included Canada. We compiled a database of communication towers in the continental United States and Canada and estimated avian mortality by tower with a regression relating avian mortality to tower height. This equation was derived from 38 tower studies for which mortality data were available and corrected for sampling effort, search efficiency, and scavenging where appropriate. Although most studies document mortality at guyed towers with steady-burning lights, we accounted for lower mortality at towers without guy wires or steady-burning lights by adjusting estimates based on published studies. The resulting estimate of mortality at towers is 6.8 million birds per year in the United States and Canada. Bootstrapped subsampling indicated that the regression was robust to the choice of studies included and a comparison of multiple regression models showed that incorporating sampling, scavenging, and search efficiency adjustments improved model fit. Estimating total avian mortality is only a first step in developing an assessment of the biological significance of mortality at communication towers for individual species or groups of species. Nevertheless, our estimate can be used to evaluate this source of mortality, develop subsequent per-species mortality estimates, and motivate policy action

Iron and the anaemia of chronic disease: a review and strategic recommendations.

BACKGROUND: The incidence of anaemia is high in many chronic conditions, yet it often receives little attention. SCOPE/METHODS: A panel of international experts with experience in haematology, nephrology, oncology, rheumatology and pharmacy was convened to prepare strategic guidelines. A focused literature search was conducted after key issues had been identified. A series of recommendations was agreed, backed, wherever possible, by published evidence which is included in the annotations. RECOMMENDATIONS: Anaemia is a critical issue for patients with chronic diseases. Healthcare professionals need to recognise that anaemia is a frequent companion of cancer and chronic conditions such as rheumatoid arthritis and heart failure. It reduces patients' quality of life and can increase morbidity and mortality. Anaemia should be considered as a disordered process in which the rate of red cell production fails to match the rate of destruction which leads eventually to a reduction in haemoglobin concentration; this process is common to all chronic anaemias. The aim of anaemia management should be to restore patient functionality and quality of life by restoring effective red cell production. Blood transfusion can elevate haemoglobin concentration in the short term but does nothing to address the underlying disorder; red cell transfusion is, therefore, not an appropriate treatment for chronic anaemia. Patients with anaemia of chronic disease may benefit from iron therapy and/or erythropoiesis stimulating agents (ESAs). Intravenous iron should be considered since this can be given safely to patients with chronic diseases while intramuscular iron causes unacceptable adverse effects and oral iron has limited efficacy in chronic anaemia. CONCLUSION: The management of anaemia calls for the development of a specialist service together with education of all healthcare professionals and transfer of skills from areas of good practice. Improvement in the management of anaemia requires a fundamental change of attitude from healthcare professionals

Zinc modulates copper coordination mode in prion protein octa-repeat subdomains

In this work we present and analyse XAS measurements carried out on various portions of Prion-protein tetra-octa-repeat peptides in complexes with Cu(II) ions, both in the presence and in the absence of Zn(II). Because of the ability of the XAS technique to provide detailed local structural information, we are able to demonstrate that Zn acts by directly interacting with the peptide, in this way competing with Cu for binding with histidine. This finding suggests that metal binding competition can be important in the more general context of metal homeostasis