1
|
Müller JP, Löf A, Mielke S, Obser T, Bruetzel LK, Vanderlinden W, Lipfert J, Schneppenheim R, Benoit M. pH-Dependent Interactions in Dimers Govern the Mechanics and Structure of von Willebrand Factor. Biophys J 2017; 111:312-322. [PMID: 27463134 DOI: 10.1016/j.bpj.2016.06.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/02/2016] [Accepted: 06/21/2016] [Indexed: 01/12/2023] Open
Abstract
Von Willebrand factor (VWF) is a multimeric plasma glycoprotein that is activated for hemostasis by increased hydrodynamic forces at sites of vascular injury. Here, we present data from atomic force microscopy-based single-molecule force measurements, atomic force microscopy imaging, and small-angle x-ray scattering to show that the structure and mechanics of VWF are governed by multiple pH-dependent interactions with opposite trends within dimeric subunits. In particular, the recently discovered strong intermonomer interaction, which induces a firmly closed conformation of dimers and crucially involves the D4 domain, was observed with highest frequency at pH 7.4, but was essentially absent at pH values below 6.8. However, below pH 6.8, the ratio of compact dimers increased with decreasing pH, in line with a previous transmission electron microscopy study. These findings indicated that the compactness of dimers at pH values below 6.8 is promoted by other interactions that possess low mechanical resistance compared with the strong intermonomer interaction. By investigating deletion constructs, we found that compactness under acidic conditions is primarily mediated by the D4 domain, i.e., remarkably by the same domain that also mediates the strong intermonomer interaction. As our data suggest that VWF has the highest mechanical resistance at physiological pH, local deviations from physiological pH (e.g., at sites of vascular injury) may represent a means to enhance VWF's hemostatic activity where needed.
Collapse
Affiliation(s)
- Jochen P Müller
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany.
| | - Achim Löf
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany
| | - Salomé Mielke
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany
| | - Tobias Obser
- Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Linda K Bruetzel
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany
| | - Willem Vanderlinden
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany; Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven, Leuven, Belgium
| | - Jan Lipfert
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany
| | - Reinhard Schneppenheim
- Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Martin Benoit
- Department of Physics and Center for Nanoscience, LMU Munich, Munich, Germany
| |
Collapse
|
2
|
Rinke J, Müller JP, Blaess MF, Chase A, Meggendorfer M, Schäfer V, Winkelmann N, Haferlach C, Cross NCP, Hochhaus A, Ernst T. Molecular characterization of EZH2 mutant patients with myelodysplastic/myeloproliferative neoplasms. Leukemia 2017. [DOI: 10.1038/leu.2017.190] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
3
|
Abstract
The process of hemostatic plug formation at sites of vascular injury crucially relies on the large multimeric plasma glycoprotein von Willebrand factor (VWF) and its ability to recruit platelets to the damaged vessel wall via interaction of its A1 domain with platelet GPIbα. Under normal blood flow conditions, VWF multimers exhibit a very low binding affinity for platelets. Only when subjected to increased hydrodynamic forces, which primarily occur in connection with vascular injury, VWF can efficiently bind to platelets. This force-regulation of VWF's hemostatic activity is not only highly intriguing from a biophysical perspective, but also of eminent physiological importance. On the one hand, it prevents undesired activity of VWF in intact vessels that could lead to thromboembolic complications and on the other hand, it enables efficient VWF-mediated platelet aggregation exactly where needed. Here, we review recent studies that mainly employed biophysical approaches in order to elucidate the molecular mechanisms underlying the complex mechano-regulation of the VWF-GPIbα interaction. Their results led to two main hypotheses: first, intramolecular shielding of the A1 domain is lifted upon force-induced elongation of VWF; second, force-induced conformational changes of A1 convert it from a low-affinity to a high-affinity state. We critically discuss these hypotheses and aim at bridging the gap between the large-scale behavior of VWF as a linear polymer in hydrodynamic flow and the detailed properties of the A1-GPIbα bond at the single-molecule level.
Collapse
Affiliation(s)
- Achim Löf
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Jochen P Müller
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Maria A Brehm
- Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| |
Collapse
|
4
|
Löf A, Müller JP, Benoit M, Brehm MA. Biophysical approaches promote advances in the understanding of von Willebrand factor processing and function. Adv Biol Regul 2017; 63:81-91. [PMID: 27717713 DOI: 10.1016/j.jbior.2016.09.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 09/19/2016] [Indexed: 06/06/2023]
Abstract
The large multimeric plasma glycoprotein von Willebrand factor (VWF) is essential for primary hemostasis by recruiting platelets to sites of vascular injury. VWF multimers respond to elevated hydrodynamic forces by elongation, thereby increasing their adhesiveness to platelets. Thus, the activation of VWF is force-induced, as is its inactivation. Due to these attributes, VWF is a highly interesting system from a biophysical point of view, and is well suited for investigation using biophysical approaches. Here, we give an overview on recent studies that predominantly employed biophysical methods to gain novel insights into multiple aspects of VWF: Electron microscopy was used to shed light on the domain structure of VWF and the mechanism of VWF secretion. High-resolution stochastic optical reconstruction microscopy, atomic force microscopy (AFM), microscale thermophoresis and fluorescence correlation spectroscopy allowed identification of protein disulfide isomerase isoform A1 as the VWF dimerizing enzyme and, together with molecular dynamics simulations, postulation of the dimerization mechanism. Advanced mass spectrometry led to detailed identification of the glycan structures carried by VWF. Microfluidics was used to illustrate the interplay of force and VWF function. Results from optical tweezers measurements explained mechanisms of the force-dependent functions of VWF's domains A1 and A2 and, together with thermodynamic approaches, increased our understanding of mutation-induced dysfunctions of platelet-binding. AFM-based force measurements and AFM imaging enabled exploration of intermonomer interactions and their dependence on pH and divalent cations. These advances would not have been possible by the use of biochemical methods alone and show the benefit of interdisciplinary research approaches.
Collapse
Affiliation(s)
- Achim Löf
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Jochen P Müller
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Martin Benoit
- Department of Physics and Center for NanoScience, LMU Munich, Munich, Germany
| | - Maria A Brehm
- Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
| |
Collapse
|
5
|
Sariisik E, Popov C, Müller JP, Docheva D, Clausen-Schaumann H, Benoit M. Decoding Cytoskeleton-Anchored and Non-Anchored Receptors from Single-Cell Adhesion Force Data. Biophys J 2016; 109:1330-3. [PMID: 26445433 PMCID: PMC4601042 DOI: 10.1016/j.bpj.2015.07.048] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 05/30/2015] [Accepted: 07/22/2015] [Indexed: 12/02/2022] Open
Abstract
Complementary to parameters established for cell-adhesion force curve analysis, we evaluated the slope before a force step together with the distance from the surface at which the step occurs and visualized the result in a two-dimensional density plot. This new tool allows detachment steps of long membrane tethers to be distinguished from shorter jumplike force steps, which are typical for cytoskeleton-anchored bonds. A prostate cancer cell line (PC3) immobilized on an atomic-force-microscopy sensor interacted with three different substrates: collagen-I (Col-I), bovine serum albumin, and a monolayer of bone marrow-derived stem cells (SCP1). To address PC3 cells’ predominant Col-I binding molecules, an antibody-blocking β1-integrin was used. Untreated PC3 cells on Col-I or SCP1 cells, which express Col-I, predominantly showed jumps in their force curves, while PC3 cells on bovine-serum-albumin- and antibody-treated PC3 cells showed long membrane tethers. The probability density plots thus revealed that β1-integrin-specific interactions are predominately anchored to the cytoskeleton, while the nonspecific interactions are mainly membrane-anchored. Experiments with latrunculin-A-treated PC3 cells corroborated these observations. The plots thus reveal details of the anchoring of bonds to the cell and provide a better understanding of receptor-ligand interactions.
Collapse
Affiliation(s)
- Ediz Sariisik
- Experimental Surgery and Regenerative Medicine, Department of Surgery, Ludwig-Maximilians-Universität München, Munich, Germany; Center for NanoScience, Ludwig-Maximilians-Universität München, Munich, Germany; Center for Applied Tissue Engineering and Regenerative Medicine, University of Applied Sciences, Munich, Germany
| | - Cvetan Popov
- Experimental Surgery and Regenerative Medicine, Department of Surgery, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jochen P Müller
- Center for NanoScience, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Denitsa Docheva
- Experimental Surgery and Regenerative Medicine, Department of Surgery, Ludwig-Maximilians-Universität München, Munich, Germany; Center for Applied Tissue Engineering and Regenerative Medicine, University of Applied Sciences, Munich, Germany
| | - Hauke Clausen-Schaumann
- Center for NanoScience, Ludwig-Maximilians-Universität München, Munich, Germany; Center for Applied Tissue Engineering and Regenerative Medicine, University of Applied Sciences, Munich, Germany
| | - Martin Benoit
- Center for NanoScience, Ludwig-Maximilians-Universität München, Munich, Germany; Center for Applied Tissue Engineering and Regenerative Medicine, University of Applied Sciences, Munich, Germany.
| |
Collapse
|
6
|
Jayavelu AK, Müller JP, Bauer R, Böhmer SA, Lässig J, Cerny-Reiterer S, Sperr WR, Valent P, Maurer B, Moriggl R, Schröder K, Shah AM, Fischer M, Scholl S, Barth J, Oellerich T, Berg T, Serve H, Frey S, Fischer T, Heidel FH, Böhmer FD. NOX4-driven ROS formation mediates PTP inactivation and cell transformation in FLT3ITD-positive AML cells. Leukemia 2015; 30:473-83. [DOI: 10.1038/leu.2015.234] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 08/04/2015] [Accepted: 08/14/2015] [Indexed: 12/21/2022]
|
7
|
Beckmann A, Xiao S, Müller JP, Mercadante D, Nüchter T, Kröger N, Langhojer F, Petrich W, Holstein TW, Benoit M, Gräter F, Özbek S. A fast recoiling silk-like elastomer facilitates nanosecond nematocyst discharge. BMC Biol 2015; 13:3. [PMID: 25592740 PMCID: PMC4321713 DOI: 10.1186/s12915-014-0113-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 12/24/2014] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND The discharge of the Cnidarian stinging organelle, the nematocyst, is one of the fastest processes in biology and involves volume changes of the highly pressurised (150 bar) capsule of up to 50%. Hitherto, the molecular basis for the unusual biomechanical properties of nematocysts has been elusive, as their structure was mainly defined as a stress-resistant collagenous matrix. RESULTS Here, we characterise Cnidoin, a novel elastic protein identified as a structural component of Hydra nematocysts. Cnidoin is expressed in nematocytes of all types and immunostainings revealed incorporation into capsule walls and tubules concomitant with minicollagens. Similar to spider silk proteins, to which it is related at sequence level, Cnidoin possesses high elasticity and fast coiling propensity as predicted by molecular dynamics simulations and quantified by force spectroscopy. Recombinant Cnidoin showed a high tendency for spontaneous aggregation to bundles of fibrillar structures. CONCLUSIONS Cnidoin represents the molecular factor involved in kinetic energy storage and release during the ultra-fast nematocyst discharge. Furthermore, it implies an early evolutionary origin of protein elastomers in basal metazoans.
Collapse
Affiliation(s)
- Anna Beckmann
- Department of Molecular Evolution and Genomics, University of Heidelberg, Centre for Organismal Studies, Im Neuenheimer Feld 329, 69120, Heidelberg, Germany.
| | - Senbo Xiao
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany.
| | - Jochen P Müller
- Applied Physics and Center for NanoScience, Ludwig Maximilian University, Amalienstr. 54, 80799, München, Germany.
| | - Davide Mercadante
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany.
| | - Timm Nüchter
- Department of Molecular Evolution and Genomics, University of Heidelberg, Centre for Organismal Studies, Im Neuenheimer Feld 329, 69120, Heidelberg, Germany.
| | - Niels Kröger
- Kirchhoff Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69210, Heidelberg, Germany.
| | | | - Wolfgang Petrich
- Kirchhoff Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69210, Heidelberg, Germany.
| | - Thomas W Holstein
- Department of Molecular Evolution and Genomics, University of Heidelberg, Centre for Organismal Studies, Im Neuenheimer Feld 329, 69120, Heidelberg, Germany.
| | - Martin Benoit
- Applied Physics and Center for NanoScience, Ludwig Maximilian University, Amalienstr. 54, 80799, München, Germany.
| | - Frauke Gräter
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany.
| | - Suat Özbek
- Department of Molecular Evolution and Genomics, University of Heidelberg, Centre for Organismal Studies, Im Neuenheimer Feld 329, 69120, Heidelberg, Germany.
| |
Collapse
|
8
|
Müller JP, Zhavoronkov N, Hertel IV, Schulz CP. Time-resolved excited state energetics of the solvated electron in sodium-doped water clusters. J Phys Chem A 2014; 118:8517-24. [PMID: 24936724 DOI: 10.1021/jp502238c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The energetics and dynamics of the first electronically excited state of solvated electron in sodium-doped water clusters has been studied, by means of time-resolved electron spectra created in a pump-probe fs-laser experiment. The Na ··· (H2O)n clusters were excited by pulses at a wavelength of 795 nm, while ionization was achieved at a wavelength of 398 nm, and the overall cross-correlation fwhm was about 50 fs. Mass-resolved electron spectra were taken using photoelectron-photoion coincidence (PEPICO) spectroscopy for cluster sizes ranging from n = 1 up to 22. The electron spectra give new insights into the dynamics of the excited state of solvated electrons in Na ··· (H2O)n clusters. These dynamics are compared to known results for water cluster anions. In both cases, the observed dynamics are a combination of solvent rearrangement and internal energy conversion.
Collapse
Affiliation(s)
- J P Müller
- Max-Born-Institute , Max-Born-Strasse 2a, 12489 Berlin, Germany
| | | | | | | |
Collapse
|
9
|
Lippok S, Obser T, Müller JP, Stierle VK, Benoit M, Budde U, Schneppenheim R, Rädler JO. Exponential size distribution of von Willebrand factor. Biophys J 2014; 105:1208-16. [PMID: 24010664 DOI: 10.1016/j.bpj.2013.07.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 07/03/2013] [Accepted: 07/24/2013] [Indexed: 12/13/2022] Open
Abstract
Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications.
Collapse
Affiliation(s)
- Svenja Lippok
- Faculty of Physics and Center for NanoScience, Ludwig Maximilian University, Munich, Germany
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Caldarelli A, Müller JP, Paskowski-Rogacz M, Herrmann K, Bauer R, Koch S, Heninger AK, Krastev D, Ding L, Kasper S, Fischer T, Brodhun M, Böhmer FD, Buchholz F. A genome-wide RNAi screen identifies proteins modulating aberrant FLT3-ITD signaling. Leukemia 2013; 27:2301-10. [PMID: 23508117 PMCID: PMC3865536 DOI: 10.1038/leu.2013.83] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 02/25/2013] [Accepted: 03/06/2013] [Indexed: 12/22/2022]
Abstract
Fms-like tyrosine kinase-3 is a commonly mutated gene in acute myeloid leukemia, with about one-third of patients carrying an internal-tandem duplication of the juxtamembrane domain in the receptor (FLT3-ITD). FLT3-ITD exhibits altered signaling quality, including aberrant activation of STAT5. To identify genes affecting FLT3-ITD-mediated STAT5 signaling, we performed an esiRNA-based RNAi screen utilizing a STAT5-driven reporter assay. Knockdowns that caused reduced FLT3-ITD-mediated STAT5 signaling were enriched for genes encoding proteins involved in protein secretion and intracellular protein transport, indicating that modulation of protein transport processes could potentially be used to reduce constitutive STAT5 signaling in FLT3-ITD-positive cells. The relevance of KDELR1, a component involved in the Golgi-ER retrograde transport, was further analyzed. In FLT3-ITD-expressing leukemic MV4-11 cells, downregulation of KDELR1 resulted in reduced STAT5 activation, proliferation and colony-forming capacity. Stable shRNA-mediated depletion of KDELR1 in FLT3-ITD-expressing 32D cells likewise resulted in reduced STAT5 signaling and cell proliferation. Importantly, these cells also showed a reduced capacity to generate a leukemia-like disease in syngeneic C3H/HeJ mice. Together our data suggest intracellular protein transport as a potential target for FLT3-ITD driven leukemias, with KDELR1 emerging as a positive modulator of oncogenic FLT3-ITD activity.
Collapse
Affiliation(s)
- A Caldarelli
- Department of Medical Systems Biology, University Hospital and Medical Faculty Carl Gustav Carus, University of Technology Dresden, Dresden, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Schmidt C, Schneble N, Müller JP, Bauer R, Perino A, Marone R, Rybalkin SD, Wymann MP, Hirsch E, Wetzker R. Phosphoinositide 3-kinase γ mediates microglial phagocytosis via lipid kinase-independent control of cAMP. Neuroscience 2012; 233:44-53. [PMID: 23276671 DOI: 10.1016/j.neuroscience.2012.12.036] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 12/18/2012] [Accepted: 12/19/2012] [Indexed: 02/08/2023]
Abstract
Microglial phagocytosis plays a key role in neuroprotective and neurodegenerative responses of the innate immune system in the brain. Here we investigated the regulatory function of phosphoinositide 3-kinase γ (PI3Kγ) in phagocytosis of bacteria and Zymosan particles by mouse brain microglia in vitro and in vivo. Using genetic and pharmacological approaches our data revealed PI3Kγ as an essential mediator of microglial phagocytosis. Unexpectedly, microglia expressing lipid kinase deficient mutant PI3Kγ exhibited similar phagocytosis as wild-type cells. These data suggest kinase-independent stimulation of cAMP phosphodiesterase activity by PI3Kγ as a crucial mediator of phagocytosis. In sum our findings indicate PI3Kγ-dependent suppression of cAMP signaling as a critical regulatory element of microglial phagocytosis.
Collapse
Affiliation(s)
- C Schmidt
- Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Jena University Hospital, 07745 Jena, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Döppner T, Müller JP, Przystawik A, Göde S, Tiggesbäumker J, Meiwes-Broer KH, Varin C, Ramunno L, Brabec T, Fennel T. Steplike intensity threshold behavior of extreme ionization in laser-driven xenon clusters. Phys Rev Lett 2010; 105:053401. [PMID: 20867915 DOI: 10.1103/physrevlett.105.053401] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Indexed: 05/29/2023]
Abstract
The generation of highly charged Xe(q+) ions up to q=24 is observed in Xe clusters embedded in helium nanodroplets and exposed to intense femtosecond laser pulses (λ=800 nm). Laser intensity resolved measurements show that the high-q ion generation starts at an unexpectedly low threshold intensity of about 10(14) W/cm2. Above threshold, the Xe ion charge spectrum saturates quickly and changes only weakly for higher laser intensities. Good agreement between these observations and a molecular dynamics analysis allows us to identify the mechanisms responsible for the highly charged ion production and the surprising intensity threshold behavior of the ionization process.
Collapse
Affiliation(s)
- T Döppner
- Institut für Physik, Universität Rostock, 18051 Rostock, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Müller JP, Schönherr C, Markova B, Bauer R, Stocking C, Böhmer FD. Role of SHP2 for FLT3-dependent proliferation and transformation in 32D cells. Leukemia 2008; 22:1945-8. [PMID: 18368066 DOI: 10.1038/leu.2008.73] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
14
|
Gautschi B, Müller JP, Schmid B, Shykoff JA. Effective number of breeders and maintenance of genetic diversity in the captive bearded vulture population. Heredity (Edinb) 2003; 91:9-16. [PMID: 12815448 DOI: 10.1038/sj.hdy.6800278] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We combined pedigree data with data derived from 14 microsatellite loci to investigate genetic diversity and its maintenance in the captive source population for the reintroduction of the bearded vulture into the Alps. We found the captive population to be genetically more variable than the largest natural population in Europe, both in terms of mean number of alleles per locus and mean observed and expected heterozygosity. Allelic diversity of the captive population was higher than, and mean heterozygosity measurements were comparable with the ones found in two large, extinct populations from Sardinia and the Alps represented by museum specimens. The amount of genetic variability recruited with the founders was still present in the captive population of the year 2000, mainly because the carriers of rare alleles were still alive. However, the decline in expected heterozygosity and the loss of alleles over generations in captivity was significant. Point estimates of effective population size, N(e), based on pedigree data and estimates of effective number of breeders, N(b), based on allele frequency changes, ranged from 20 to 30 and were significantly smaller than the census size. The results demonstrate that the amount of genetic variability in the captive bearded vulture population is comparable or even larger than the amount present in natural populations. However, the population is in danger to lose genetic variability over time because of genetic drift. Management strategies should therefore aim at preserving genetic variability by minimising kinship, and at increasing N(e) by recruiting additional founders and enhancing gene flow between the released, the captive and natural populations.
Collapse
Affiliation(s)
- B Gautschi
- Institute of Environmental Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | | | | | | |
Collapse
|
15
|
Abstract
In Escherichia coli, SecA is a critical component of the protein transport machinery which powers the translocation process by hydrolyzing ATP and recognizing signal peptides which are the earmark of secretory proteins. In contrast, SecB is utilized by only a subset of preproteins to prevent their premature folding and chaperone them to membrane-bound SecA. Using purified components and synthetic signal peptides, we have studied the interaction of SecB with SecA and with SecA-signal peptide complexes in vitro. Using a chemical cross-linking approach, we find that the formation of SecA-SecB complexes is accompanied by a decrease in the level of cross-linking of SecA dimers, suggesting that SecB induces a conformational change in SecA. Furthermore, functional signal peptides, but not dysfunctional ones, promote the formation of SecA-SecB complexes. SecB is also shown to directly enhance the ATPase activity of SecA in a concentration-dependent and saturable manner. To determine the biological consequence of this finding, the influence of SecB on the signal peptide-stimulated SecA/lipid ATPase was studied using synthetic peptides of varying hydrophobicity. Interestingly, the presence of SecB can sufficiently boost the response of signal peptides with moderate hydrophobicity such that it is comparable to the activity generated by a more hydrophobic peptide in the absence of SecB. The results suggest that SecB directly enhances the activity of SecA and provide a biochemical basis for the enhanced transport efficiency of preproteins in the presence of SecB in vivo.
Collapse
Affiliation(s)
- J Kim
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
| | | | | | | | | |
Collapse
|
16
|
Gautschi B, Tenzer I, Müller JP, Schmid B. Isolation and characterization of microsatellite loci in the bearded vulture (Gypaetus barbatus) and cross-amplification in three old world vulture species. Mol Ecol 2000; 9:2193-5. [PMID: 11123649 DOI: 10.1046/j.1365-294x.2000.105321.x] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- B Gautschi
- Institut für Umweltwissenschaften, Universität Zürich-Irchel, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | | | | | | |
Collapse
|
17
|
Müller JP, Ozegowski J, Vettermann S, Swaving J, Van Wely KH, Driessen AJ. Interaction of Bacillus subtilis CsaA with SecA and precursor proteins. Biochem J 2000; 348 Pt 2:367-73. [PMID: 10816431 PMCID: PMC1221075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
CsaA from the Gram-positive bacterium Bacillus subtilis has been identified previously as a suppressor of the growth and protein-export defect of Escherichia coli secA(Ts) mutants. CsaA has chaperone-like activities in vivo and in vitro. To examine the role of CsaA in protein export in B. subtilis, expression of the csaA gene was repressed. While export of most proteins remained unaffected, export of at least two proteins was significantly reduced upon CsaA depletion. CsaA co-immunoprecipitates and co-purifies with the SecA proteins of E. coli and B. subtilis, and binds the B. subtilis preprotein prePhoB. Purified CsaA stimulates the translocation of prePhoB into E. coli membrane vesicles bearing the B. subtilis translocase, whereas it interferes with the SecB-mediated translocation of proOmpA into membrane vesicles of E. coli. The specific interaction with the SecA translocation ATPase and preproteins suggests that CsaA acts as a chaperone that promotes the export of a subset of preproteins in B. subtilis.
Collapse
Affiliation(s)
- J P Müller
- Institute for Molecular Biology, Jena University, Winzerlaer Strasse 10, D-07745 Jena, Germany.
| | | | | | | | | | | |
Collapse
|
18
|
Abstract
The localisation of phosphate-starvation-induced phosphodiesterase PhoD from Bacillus subtilis was studied by analysing processing, release and immunogold labelling of the sections. Although the processing of the pre-protein was extremely slow, the major fraction of PhoD could be detected at the surface of the cell wall. The results indicate that inefficient processing of the translocated pre-protein keeps PhoD in a cell wall-associated location. The uncleaved signal peptide might function as a membrane anchor.
Collapse
Affiliation(s)
- J P Müller
- Institute of Molecular Biology, Jena University, Winzerlaer Str. 10, D-07745, Jena, Germany.
| | | |
Collapse
|
19
|
Abstract
Protein translocation through the cytoplasmic membrane of Escherichia coli involves cytosolic chaperones. The export-dedicated chaperone SecB mediates targeting of a subset of pre-proteins. In this report, synthesis of SecB in response to plasmid-mediated overexpression of pre-proteins was studied. Overexpression of SecB-dependent pre-proteins stimulated synthesis of SecB under conditions where the cellular export capacity was saturated or uncomplexed SecB was trapped. On the contrary, overexpression of SecB-independent pre-beta-lactamase reduced the promoter activity of secB. The results suggest that uncomplexed SecB can be sequestered by synthesis of SecB-dependent pre-proteins. Furthermore, these data demonstrate the distinct action of the SecB- and signal recognition particle-dependent protein targeting pathways.
Collapse
Affiliation(s)
- J P Müller
- Institute for Molecular Biology, Jena University, Germany.
| |
Collapse
|
20
|
Abstract
The secretion of proteins from Bacillus subtilis was studied under physiologically well-defined conditions in continuous cultures at a range of specific growth rates. The kinetics of secretion was analysed by using pulse-chase and immunoprecipitation techniques that allowed both processing and release to be monitored. Growth conditions were selected that were known to lead to significant changes in the anionic polymer composition of the cell wall. Under magnesium limitation only low levels of native proteins were released into the growth medium. In contrast, much higher amounts of released protein were observed under phosphate limitation. Although synthesis of native secretory proteins appeared to be highly regulated, only minor changes in the secretion of heterologous proteins were detected. Comparable kinetics of protein release of cells grown under different conditions indicated similar cell wall permeabilities. The large changes in the amounts of released proteins were not reflected in the production of chaperones and components required fro protein secretion. The data suggest that the capacity of the secretion machinery is not a major limiting step in the export of native secretory proteins.
Collapse
Affiliation(s)
- J P Müller
- Institut für Molekularbiologie, Friedrich-Schiller-Universität, Jena, Germany.
| | | |
Collapse
|
21
|
Abstract
The efficient export of proteins through the cytoplasmic membrane of Escherichia coli requires chaperones to maintain protein precursors in a translocation-competent conformation. In addition to SecB, the major chaperone facilitating export of particular precursors, heat shock-induced chaperones DnaK-DnaJ and GroEL-GroES are also involved in this process. By use of secB'-lacZ gene fusions and immunoprecipitation experiments, SecB production was studied in E. coli strains containing conditional lethal mutations in chaperone or sec genes. While the loss of heat shock chaperones resulted in an increased production of SecB, mutations in sec genes showed only minor effects on SecB synthesis. Neither the plasmid-mediated overexpression of precursors of exoproteins nor the overexpression of secB altered the synthesis of SecB. These results suggest that under conditions where chaperones become depleted, E. coli responds by raising the expression of secB. These data confirm the supposed synergy of different chaperones involved in protein export.
Collapse
Affiliation(s)
- J P Müller
- Institute for Molecular Biology, Friedrich Schiller University, Jena, Germany.
| |
Collapse
|
22
|
Abstract
Toxic damage of brain cells by aluminium (Al) is discussed as a possible factor in the development of neurodegenerative disorders in humans. To investigate neurotoxic effects of Al, serum-free cultures of mechanically dissociated embryonic chick (stage 28-29) forebrain, brain stem and optic tectum, and for comparison meningeal cells, were treated with Al (0-1000 microM) for 7 days. Effects of Al on cell viability (lysosomal and mitochondrial activity) and differentiation (synthesis of cell-specific proteins) were found to the brain area specific with the highest sensitivity observed in optic tectum. No inhibiting effects on cell viability could be observed in cultures of forebrain and meninges in the concentration range tested. In all three brain tissue cultures, threshold levels for the reduction of cell differentiation parameters were found at lower concentrations [concentration resulting in a 50% decrease (IC50) > 180 microM] than for the inhibition of cell viability (IC50 > 280 microM), indicating a specific toxic potential of Al for cytoskeletal alterations. The culture levels of nerve cell-specific markers microtubule-associated protein type 2 (the most sensitive parameter) and the 68-kDa neurofilament were inhibited at lower concentrations (IC50 180-630 microM) than the astrocyte-specific glial fibrillary acidic protein (IC50 700-approximately 1000 microM), demonstrating a particularly high sensitivity of neurons in comparison to astrocytes. Based on these differences in Al sensitivity observed for different cell markers in the various brain tissue cultures, the in vitro system used in the present study proved to be a suitable model to assess brain area and cell type-specific neurotoxic effects of Al.
Collapse
Affiliation(s)
- J P Müller
- Institute of Toxicology, ETH and University of Zürich, Switzerland
| | | |
Collapse
|
23
|
Müller JP, Steinegger A, Schlatter C. Contribution of aluminum from packaging materials and cooking utensils to the daily aluminum intake. Z Lebensm Unters Forsch 1993; 197:332-41. [PMID: 8249476 DOI: 10.1007/bf01242057] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Migration of aluminum (Al) from packaging materials and cooking utensils into foods and beverages was determined at intervals during cooking or during storage by graphite furnace atomic absorption spectroscopy. High amounts of Al migrated into acidic products such as mashed tomatoes during normal processing in normal, non-coated Al pans. After 60 min cooking an Al content of 10-15 mg/kg was measured in tomato sauce. Surprisingly, the Al concentration was also increased up to 2.6 mg/L after boiling tap water for 15 min in Al pans. Storage of Coca-Cola in internally lacquered Al cans resulted in Al levels below 0.25 mg/L. In contrast, non-coated Al camping bottles containing lime blossom tea acidified with lemon juice released up to 7 mg Al/L within 5 days. The Al concentration in coffee was lower than that of the tap water used in its preparation, even if prepared in Al heaters. In Switzerland, where most pans nowadays are made of stainless steel or teflon-coated Al, the average contribution for the use of Al utensils to the daily Al intake of 2-5 mg from the diet is estimated to be less than 0.1 mg.
Collapse
Affiliation(s)
- J P Müller
- Institute of Toxicology, Swiss Federal Institute of Technology, University of Zürich
| | | | | |
Collapse
|
24
|
Müller JP, Koch P. [Peri-articular ossification in total hip prostheses]. Orthopade 1989; 18:511-6. [PMID: 2514402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The frequency and predisposing factors of ectopic bone formation (EBF) after total hip arthroplasty (THA) are analyzed in 6026 primary THA documented at the M.E. Mueller Foundation in Berne. Series from two clinics [the Lindenhof Clinic in Berne (n = 816) and the Wilhelm Schulthess Clinic in Zürich (n = 612)] are analyzed separately and the results compared with those in the literature. Overall EBF was found in 38.3% of the patients; in 8.6%, it was clinically obvious (grades III and IV according to the classification of Brooker et al.) and is analyzed in this study. EBF was found in 13.4% of the men compared with 4.2% of the women. The frequency of EBF was found to be particularly low in patients with rheumatoid arthritis (4.4%), and EBF was found in 11.4% of patients with post-traumatic osteoarthritis and in 11.1% with idiopathic necrosis of the femoral head. Severe preoperatively limited hip movement did not significantly increase the risk of EBF (11.9%), nor did previous hip surgery, such as intertrochanteric osteotomy (11.3%). Postoperative hematoma that led to puncture or even evacuation was responsible in 14.4%. The therapeutic and prophylactic possibilities are compared with those in the literature, and our personal observations are discussed.
Collapse
|
25
|
Munzinger U, Baumgartner H, Müller JP. [Rehabilitation of the knee joint]. Ther Umsch 1984; 41:67-74. [PMID: 6701817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|