Tetraspanin 6: a pivotal protein of the multiple vesicular body determining exosome release and lysosomal degradation of amyloid precursor protein fragments

BACKGROUND: The mechanisms behind Aβ-peptide accumulation in non-familial Alzheimer’s disease (AD) remain elusive. Proteins of the tetraspanin family modulate Aβ production by interacting to γ-secretase. METHODS: We searched for tetraspanins with altered expression in AD brains. The function of the selected tetraspanin was studied in vitro and the physiological relevance of our findings was confirmed in vivo. RESULTS: Tetraspanin-6 (TSPAN6) is increased in AD brains and overexpression in cells exerts paradoxical effects on Amyloid Precursor Protein (APP) metabolism, increasing APP-C-terminal fragments (APP-CTF) and Aβ levels at the same time. TSPAN6 affects autophagosome-lysosomal fusion slowing down the degradation of APP-CTF. TSPAN6 recruits also the cytosolic, exosome-forming adaptor syntenin which increases secretion of exosomes that contain APP-CTF. CONCLUSIONS: TSPAN6 is a key player in the bifurcation between lysosomal-dependent degradation and exosome mediated secretion of APP-CTF. This corroborates the central role of the autophagosomal/lysosomal pathway in APP metabolism and shows that TSPAN6 is a crucial player in APP-CTF turnover

International consensus on the most useful physical examination tests used by physiotherapists for patients with headache: A Delphi study

Background: A wide range of physical tests have been published for use in the assessment of musculoskeletal dysfunction in patients with headache. Which tests are used depends on a physiotherapist's clinical and scientific background as there is little guidance on the most clinically useful tests. Objectives: To identify which physical examination tests international experts in physiotherapy consider the most clinically useful for the assessment of patients with headache. Design/methods: Delphi survey with pre-specified procedures based on a systematic search of the literature for physical examination tests proposed for the assessment of musculoskeletal dysfunction in patients with headache. Results: Seventeen experts completed all three rounds of the survey. Fifteen tests were included in round one with eleven additional tests suggested by the experts. Finally eleven physical examination tests were considered clinically useful: manual joint palpation, the cranio-cervical flexion test, the cervical flexion-rotation test, active range of cervical movement, head forward position, trigger point palpation, muscle tests of the shoulder girdle, passive physiological intervertebral movements, reproduction and resolution of headache symptoms, screening of the thoracic spine, and combined movement tests. Conclusions: Eleven tests are suggested as a minimum standard for the physical examination of musculoskeletal dysfunctions in patients with headache

Re-identification of clinical isolates of the Pseudallescheria boydii-complex involved in near-drowning.

Fungal infections caused by the members of the genera Pseudallescheria and/or Scedosporium are important complications in patients after near-drowning. As the taxonomy of Pseudallescheria and Scedosporium has been revised, clinical isolates from 11 patients, after near-drowning, previously identified as P. boydii or S. apiospermum had to be re-identified. S. apiospermum, now separated from P. boydii as a distinct species, was found most frequently (n = 8), while S. aurantiacum, recently described as new species and P. boydii were less common (n = 2 and n = 1, respectively). Three patients near-drowned during the Tsunami 2004 were infected by different species of the P. boydii complex. In vitro testing resulted in lowest minimal inhibitory concentration (MICs) for voriconazole (range 0.25-2.0 microg ml(-1))

A review of German Scedosporium prolificans cases from 1993 to 2007

Scedosporium prolificans is one of the most life-threatening fungal opportunistic pathogens due to its high resistance to common systemic antifungal agents. While a close relative of Pseudallescheria boydii, S. prolificans has a more limited geographic range being primarily found in Australia, USA and Spain. Infections have also been reported from several other European countries and from Chile. Twenty patients with Scedosporium prolificans infection or colonization from August 1993 to May 2007 were retrospectively reviewed in Germany. They had all been identified at or reported to the Reference Laboratory for Pseudallescheria/Scedosporium spp. in Berlin. Twelve of 13 patients with haematological disorders and/or on immunosuppressive therapy developed a fatal invasive scedosporiosis. Colonization of the respiratory tract was reported for one patient after heart-lung-transplantation, all six patients with cystic fibrosis and one with chronic sinusitis. Molecular studies of the S. prolificans isolates confirmed that parts of the 18S, the Internal Transcribed Spacer (ITS) regions and the D1/D2 domain of the 28S region of rDNA are monomorphic. However, sequencing of parts of the translation elongation factor EF1-alpha (EF-1alpha) and the chitin synthase (CHS-1) genes revealed the presence of three and two distinct genotypes, respectively. Two informative mutations were found in EF-1alpha and a single nucleotide exchange in the CHS-1 gene

The dynamic conformational landscape of -secretase

The structure and function of the γ-secretase proteases are of great interest because of their crucial roles in cellular and disease processes. We established a novel purification protocol for the γ-secretase complex that involves a conformation- and complex-specific nanobody, yielding highly pure and active enzyme. Using single particle electron microscopy, we analyzed the γ-secretase structure and its conformational variability. Under steady-state conditions, the complex adopts three major conformations, which differ in overall compactness and relative position of the nicastrin ectodomain. Occupancy of the active or substrate-binding sites by inhibitors differentially stabilizes subpopulations of particles with compact conformations, whereas a mutation linked to familial Alzheimer disease results in enrichment of extended-conformation complexes with increased flexibility. Our study presents the γ-secretase complex as a dynamic population of interconverting conformations, involving rearrangements at the nanometer scale and a high level of structural interdependence between subunits. The fact that protease inhibition or clinical mutations, which affect amyloid β (Aβ) generation, enrich for particular subpopulations of conformers indicates the functional relevance of the observed dynamic changes, which are likely to be instrumental for highly allosteric behavior of the enzyme

Deficiency of Aph1B/C-γ-secretase disturbs Nrg1 cleavage and sensorimotor gating that can be reversed with antipsychotic treatment

Regulated intramembrane proteolysis by γ-secretase cleaves proteins in their transmembrane domain and is involved in important signaling pathways. At least four different γ-secretase complexes have been identified, but little is known about their biological role and specificity. Previous work has demonstrated the involvement of the Aph1A-γ-secretase complex in Notch signaling, but no specific function could be assigned to Aph1B/C-γ-secretase. We demonstrate here that the Aph1B/C-γ-secretase complex is expressed in brain areas relevant to schizophrenia pathogenesis and that Aph1B/C deficiency causes pharmacological and behavioral abnormalities that can be reversed by antipsychotic drugs. At the molecular level we find accumulation of Nrg1 fragments in the brain of Aph1BC−/− mice. Our observations gain clinical relevance by the demonstration that a Val-to-Leu mutation in the Nrg1 transmembrane domain, associated with increased risk for schizophrenia, affects γ-secretase cleavage of Nrg1. This finding suggests that dysregulation of intramembrane proteolysis of Nrg1 could increase risk for schizophrenia and related disorders