Tyrosinphosphorylierung als Regulator der Reifung von Rezeptortyrosinkinasen

Die RezeptortyrosinkinaseFLT-3istin frühen myeloidenund B-lymphoidenVorläuferzellen exprimiert und spielt eine wichtige Rolle bei der normalen Differenzierung hämatopoetischer Zellen. Fehlerhafte Aktivität von FLT-3 ist mit akuter myeloischer Leukämie (AML) assoziiert. In etwa 30 % aller AML-Fälle treten Mutationen im FLT-3-Gen auf, die eine konstitutiv aktive Kinase zur Folge haben. Die am häufigsten auftretende Mutationen sind die sg. “internal tandem duplications” (ITD) in der Juxtamembrandomäne. FLT-3 mit ITD Mutation induziert ein anderes Muster an aktivierten Signalwegen als FLT-3 WT, was eine wichtige Rolle bei der Transformation spielt. Der Grund für das veränderte Signalverhalten war bisher unbekannt. In der vorliegenden Arbeit können wir zeigen, dass FLT-3 ITD nicht effizient reift und partiell im endoplasmatischen Retikulum zurückgehalten wird und dass die-se Retention abhängig von seiner Kinaseaktivität ist. Hemmung der Kinaseaktivität durch Inhibitoren, Mutationen oder Coexpression von PTPasen resultierte in einer normalen Reifung des Rezeptors. Wir können ebenfalls zeigen, dass FLT-3 ITD im ER Qualitätskontrollsystem zurückgehalten wird und von molekularen Chaperonen wie Calnexin, HSP90 und ERp57 abhängig ist. Diese Abhängigkeit kann pharmakologisch ausgenutzt werden. Zudem können wir zeigen, dass ER Retention nicht nur bei onkogenem FLT-3 sondern allgemein bei hyperphosphorylierten Rezeptortyrosinkinasen auftritt und demnach Tyrosinphosphorylierung demnach ein allgemeiner gültiges Regulationsprinzip bei der Reifung von Rezeptortyrosinkinasen ist

ADAM and ADAMTS Proteases in Hepatic Disorders

Proteolysis is an irreversible post-translational modification that regulates protein function and signal transduction. This includes remodelling of the extracellular matrix, release of membrane-bound cytokines and receptor ectodomains, as well as the initiation of intracellular signalling cues. Members of the adamalysin protease subfamily, in particular the ADAM (a disintegrin and metalloprotease) and ADAMTS (the ADAM containing thrombospondin motif) families, are involved in these processes. This review presents an overview of how ADAM and ADAMTS proteins are involved in liver physiology and pathophysiology

Transgenic analysis of the Leishmania MAP kinase MPK10 reveals an auto-inhibitory mechanism crucial for stage-regulated activity and parasite viability

Protozoan pathogens of the genus Leishmania have evolved unique signaling mechanisms that can sense changes in the host environment and trigger adaptive stage differentiation essential for host cell infection. The signaling mechanisms underlying parasite development remain largely elusive even though Leishmania mitogen-activated protein kinases (MAPKs) have been linked previously to environmentally induced differentiation and virulence. Here, we unravel highly unusual regulatory mechanisms for Leishmania MAP kinase 10 (MPK10). Using a transgenic approach, we demonstrate that MPK10 is stage-specifically regulated, as its kinase activity increases during the promastigote to amastigote conversion. However, unlike canonical MAPKs that are activated by dual phosphorylation of the regulatory TxY motif in the activation loop, MPK10 activation is independent from the phosphorylation of the tyrosine residue, which is largely constitutive. Removal of the last 46 amino acids resulted in significantly enhanced MPK10 activity both for the recombinant and transgenic protein, revealing that MPK10 is regulated by an auto-inhibitory mechanism. Over-expression of this hyperactive mutant in transgenic parasites led to a dominant negative effect causing massive cell death during amastigote differentiation, demonstrating the essential nature of MPK10 auto-inhibition for parasite viability. Moreover, phosphoproteomics analyses identified a novel regulatory phospho-serine residue in the C-terminal auto-inhibitory domain at position 395 that could be implicated in kinase regulation. Finally, we uncovered a feedback loop that limits MPK10 activity through dephosphorylation of the tyrosine residue of the TxY motif. Together our data reveal novel aspects of protein kinase regulation in Leishmania, and propose MPK10 as a potential signal sensor of the mammalian host environment, whose intrinsic pre-activated conformation is regulated by auto-inhibition

GNSS Remote Sensing:Overview and selected recent developments

Ponencia expuesta online en el 8th International Radio Occultation Working Group Meeting (2021) celebrado del 7 al 9 de abrilGround and satellite based GNSS Remote Sensing (GNSS-RS) developed during the recent two decades into a very powerful and versatile tool for Earth System Research. A highlight of these developments is the operational use of spaceborne GNSS Radio Occultation (RO) data from several satellite missions to improve day-by-day global weather predictions. GNSS Remote Sensing is briefly introduced with selected applications. One prominent example is the improvement of regional and global weather forecasts. GNSS signals, reflected from water, ice and land surfaces (GNSS-Reflectometry, GNSS-R) can usefully complement the observation capabilities of GNSS-RO mission and enable versatile additional geophysical applications such as observation of wind speed and precipitation over oceans, which are illustrated. Finally, selected aspects for a comprehensive GNSS based Earth Observation with small satellite constellations are presented

Wave activity at ionospheric heights above the Andes Mountains detected from FORMOSAT-3/COSMIC GPS radio occultation data

An estimation of the ionospheric wave activity, derived from 4 years of FORMOSAT-3/ COSMIC GPS (Taiwan's Formosa Satellite Mission 3/Constellation Observing System for Meteorology—Global Positioning System) radio occultation electron density data, is presented. A systematic enhancement at the eastern side of the Andes range with respect to the western side is observed. A fitting method to remove the wavelike component from each measured profile and estimate the wave activity is described. The differential effect introduced by the action of orography on the generation, to the eastern side of the Andes, of mountain waves, deep convection waves, or even secondary waves aloft after momentum deposition in the middle atmosphere, is suggested.Fil: de la Torre, Alejandro. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alexander, Pedro Manfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nava, B.. The Abdus Salam; ItaliaFil: Radicella, S.. The Abdus Salam; ItaliaFil: Schmidt, T.. Helmholtz Centre Potsdam; AlemaniaFil: Wickert, J.. Helmholtz Centre Potsdam; Alemani

Roles for ADAM17 in TNF-R1 Mediated Cell Death and Survival in Human U937 and Jurkat Cells

Signaling via death receptor family members such as TNF-R1 mediates pleiotropic biological outcomes ranging from inflammation and proliferation to cell death. Pro-survival signaling is mediated via TNF-R1 complex I at the cellular plasma membrane. Cell death induction requires complex IIa/b or necrosome formation, which occurs in the cytoplasm. In many cell types, full apoptotic or necroptotic cell death induction requires the internalization of TNF-R1 and receptosome formation to properly relay the signal inside the cell. We interrogated the role of the enzyme A disintegrin and metalloprotease 17 (ADAM17)/TACE (TNF-α converting enzyme) in death receptor signaling in human hematopoietic cells, using pharmacological inhibition and genetic ablation. We show that in U937 and Jurkat cells the absence of ADAM17 does not abrogate, but rather increases TNF mediated cell death. Likewise, cell death triggered via DR3 is enhanced in U937 cells lacking ADAM17. We identified ADAM17 as the key molecule that fine-tunes death receptor signaling. A better understanding of cell fate decisions made via the receptors of the TNF-R1 superfamily may enable us, in the future, to more efficiently treat infectious and inflammatory diseases or cancer

Tetraspanin 8 is an interactor of the metalloprotease meprin β within tetraspanin-enriched microdomains

Meprin β is a dimeric type I transmembrane protein and acts as an ectodomain sheddase at the cell surface. It has been shown that meprin β cleaves the amyloid precursor protein (APP), thereby releasing neurotoxic amyloid β peptides and implicating a role of meprin β in Alzheimer's disease. In order to identify non-proteolytic regulators of meprin β, we performed a split ubiquitin yeast two-hybrid screen using a small intestinal cDNA library. In this screen we identified tetraspanin 8 (TSPAN8) as interaction partner for meprin β. As several members of the tetraspanin family were described to interact with metalloproteases thereby affecting their localization and/or activity, we hypothesized similar functions of TSPAN8 in the regulation of meprin β. We employed cell biological methods to confirm direct binding of TSPAN8 to meprin β. Surprisingly, we did not observe an effect of TSPAN8 on the catalytic activity of meprin β nor on the specific cleavage of its substrate APP. However, both proteins were identified as present in tetraspanin-enriched microdomains. Therefore we hypothesize that TSPAN8 might be important for the orchestration of meprin β at the cell surface with impact on certain proteolytic processes that have to be further identified

Stable magnetic equilibria and their evolution in the upper main sequence, white dwarfs, and neutron stars

[abbreviated] Long-lived, large-scale magnetic field configurations exist in upper main sequence, white dwarf, and neutron stars. Externally, these fields have a strong dipolar component, while their internal structure and evolution are uncertain, but highly relevant for several problems in stellar and high-energy astrophysics. We discuss the main properties expected for the stable magnetic configurations in these stars from physical arguments, and how these properties may determine the modes of decay of these configurations. Stable magneto-hydrostatic equilibria are likely to exist in stars whenever the matter in their interior is stably stratified (not barotropic). These equilibria are not force-free and not required to satisfy the Grad-Shafranov equation, but they do involve both toroidal and poloidal field components. We argue that the main mode of decay for these configurations are processes that lift the constraints set by stable stratification, such as heat diffusion in main-sequence envelopes and white dwarfs, and beta decays or particle diffusion in neutron stars. In the former, heat diffusion is not fast enough to make these equilibria evolve over the stellar lifetime. In neutron stars, a strong enough field might decay by overcoming the compositional stratification through beta decays (at the highest field strengths) or through ambipolar diffusion (for somewhat weaker fields). These processes convert magnetic energy to thermal energy, and they occur at significant rates only once the latter is smaller than the former, and therefore they substantially delay the cooling of the neutron star, while slowly decreasing its magnetic energy.Comment: 11 pages, 1 figure, accepted by A&A. This version has been revised according to the referee's and editor's comments and suggestions, and a few signs were corrected in sec. 2.

Cyclosporin A Treatment of Leishmania donovani Reveals Stage-Specific Functions of Cyclophilins in Parasite Proliferation and Viability

BACKGROUND: Cyclosporin A (CsA) has important anti-microbial activity against parasites of the genus Leishmania, suggesting CsA-binding cyclophilins (CyPs) as potential drug targets. However, no information is available on the genetic diversity of this important protein family, and the mechanisms underlying the cytotoxic effects of CsA on intracellular amastigotes are only poorly understood. Here, we performed a first genome-wide analysis of Leishmania CyPs and investigated the effects of CsA on host-free L. donovani amastigotes in order to elucidate the relevance of these parasite proteins for drug development. METHODOLOGY/PRINCIPAL FINDINGS: Multiple sequence alignment and cluster analysis identified 17 Leishmania CyPs with significant sequence differences to human CyPs, but with highly conserved functional residues implicated in PPIase function and CsA binding. CsA treatment of promastigotes resulted in a dose-dependent inhibition of cell growth with an IC50 between 15 and 20 µM as demonstrated by proliferation assay and cell cycle analysis. Scanning electron microscopy revealed striking morphological changes in CsA treated promastigotes reminiscent to developing amastigotes, suggesting a role for parasite CyPs in Leishmania differentiation. In contrast to promastigotes, CsA was highly toxic to amastigotes with an IC50 between 5 and 10 µM, revealing for the first time a direct lethal effect of CsA on the pathogenic mammalian stage linked to parasite thermotolerance, independent from host CyPs. Structural modeling, enrichment of CsA-binding proteins from parasite extracts by FPLC, and PPIase activity assays revealed direct interaction of the inhibitor with LmaCyP40, a bifunctional cyclophilin with potential co-chaperone function. CONCLUSIONS/SIGNIFICANCE: The evolutionary expansion of the Leishmania CyP protein family and the toxicity of CsA on host-free amastigotes suggest important roles of PPIases in parasite biology and implicate Leishmania CyPs in key processes relevant for parasite proliferation and viability. The requirement of Leishmania CyP functions for intracellular parasite survival and their substantial divergence form host CyPs defines these proteins as prime drug targets