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Tobias baumgart

Samantha E Wilner, Qi Xiao, Zachary Tobias Graber, Samuel E Sherman, Virgil Percec, Tobias Baumgart
Lamellar to non-lamellar membrane shape transitions play essential roles in key cellular processes, such as membrane fusion and fission, and occur in response to external stimuli, including drug treatment and heat. A subset of these transitions can be modeled by means of thermally inducible amphiphile assemblies. We previously reported on mixtures of hydrogenated, fluorinated, and hybrid Janus dendrimers (JDs) that self-assemble into complex dendrimersomes (DMSs), including dumbbells, and serve as promising models for understanding the complexity of biological membranes...
April 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Chun Liu, Sanghamitra Deb, Vinicius S Ferreira, Eric Xu, Tobias Baumgart
Phosphatidylinositides play important roles in cellular signaling and migration. Phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) is an important phosphatidylinositide because it acts as a secondary messenger to trigger cell movement and proliferation. A high level of PI(3,4,5)P3 at the plasma membrane is known to contribute to tumorigenesis. One key enzyme that regulates PI(3,4,5)P3 levels at the plasma membrane is phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which dephosphorylates PI(3,4,5)P3 through hydrolysis to form phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2)...
2018: PloS One
Katarzyna I Jankowska, Edward K Williamson, Nathan H Roy, Daniel Blumenthal, Vidhi Chandra, Tobias Baumgart, Janis K Burkhardt
Full T cell activation requires coordination of signals from multiple receptor-ligand pairs that interact in parallel at a specialized cell-cell contact site termed the immunological synapse (IS). Signaling at the IS is intimately associated with actin dynamics; T cell receptor (TCR) engagement induces centripetal flow of the T cell actin network, which in turn enhances the function of ligand-bound integrins by promoting conformational change. Here, we have investigated the effects of integrin engagement on actin flow, and on associated signaling events downstream of the TCR...
2018: Frontiers in Immunology
Ramakrishnan Natesan, K K Sreeja, Arpita Roychoudhuri, David M Eckmann, Portonovo S Ayyaswamy, Tobias Baumgart, Thomas Pucadyil, Shivprasad Vitthal Patil, Valerie M Weaver, Ravi Radhakrishnan
Thermal fluctuations in cell membranes manifest as an excess area (Aex) which governs a multitude of physical process at the sub-micron scale. We present a theoretical framework, based on an in silico tether pulling method, which may be used to reliably estimate Aex in live cells. We perform our simulations in two different thermodynamic ensembles: (i) the constant projected area and (ii) the constant frame tension ensembles and show the equivalence of our results in the two. The tether forces estimated from our simulations compare well with our experimental measurements for tethers extracted from ruptured GUVs and HeLa cells...
November 8, 2017: Physical Biology
Frank Bicker, Verica Vasic, Guilherme Horta, Felipe Ortega, Hendrik Nolte, Atria Kavyanifar, Stefanie Keller, Nevenka Dudvarski Stankovic, Patrick N Harter, Rui Benedito, Beat Lutz, Tobias Bäuerle, Jens Hartwig, Jan Baumgart, Marcus Krüger, Konstantin Radyushkin, Lavinia Alberi, Benedikt Berninger, Mirko H H Schmidt
Adult neural stem cells reside in a specialized niche in the subventricular zone (SVZ). Throughout life they give rise to adult-born neurons in the olfactory bulb (OB), thus contributing to neural plasticity and pattern discrimination. Here, we show that the neurovascular protein EGFL7 is secreted by endothelial cells and neural stem cells (NSCs) of the SVZ to shape the vascular stem-cell niche. Loss of EGFL7 causes an accumulation of activated NSCs, which display enhanced activity and re-entry into the cell cycle...
June 28, 2017: Nature Communications
Vijith Vijayan, Tumpara Srinu, Srikanth Karnati, Vannuruswamy Garikapati, Monika Linke, Lilit Kamalyan, Srihari Reddy Mali, Kritika Sudan, Andreas Kollas, Tobias Schmid, Sabine Schulz, Bernhard Spengler, Thomas Weichhart, Stephan Immenschuh, Eveline Baumgart-Vogt
Peroxisomes are proposed to play an important role in the regulation of systemic inflammation; however, the functional role of these organelles in inflammatory responses of myeloid immune cells is largely unknown. In this article, we demonstrate that the nonclassical peroxisome proliferator 4-phenyl butyric acid is an efficient inducer of peroxisomes in various models of murine macrophages, such as primary alveolar and peritoneal macrophages and the macrophage cell line RAW264.7, but not in primary bone marrow-derived macrophages...
March 15, 2017: Journal of Immunology: Official Journal of the American Association of Immunologists
Conor M Haney, Christina L Cleveland, Rebecca F Wissner, Lily Owei, Jaclyn Robustelli, Malcolm J Daniels, Merve Canyurt, Priscilla Rodriguez, Harry Ischiropoulos, Tobias Baumgart, E James Petersson
Fibrillar aggregates of the protein α-synuclein (αS) are one of the hallmarks of Parkinson's disease. Here, we show that measuring the fluorescence polarization (FP) of labels at several sites on αS allows one to monitor changes in the local dynamics of the protein after binding to micelles or vesicles, and during fibril formation. Most significantly, these site-specific FP measurements provide insight into structural remodeling of αS fibrils by small molecules and have the potential for use in moderate-throughput screens to identify small molecules that could be used to treat Parkinson's disease...
February 7, 2017: Biochemistry
Ningwei Li, Nima Sharifi-Mood, Fuquan Tu, Daeyeon Lee, Ravi Radhakrishnan, Tobias Baumgart, Kathleen J Stebe
Inspired by proteins that generate membrane curvature, sense the underlying membrane geometry, and migrate driven by curvature gradients, we explore the question: Can colloids, adhered to lipid bilayers, also sense and respond to membrane geometry? We report the migration of Janus microparticles adhered to giant unilamellar vesicles elongated to present spatially varying curvatures. In our experiments, colloids migrate only when the membranes are tense, suggesting that they migrate to minimize membrane area...
January 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Zhiming Chen, Ehsan Atefi, Tobias Baumgart
Peripheral proteins can bend membranes through several different mechanisms, including scaffolding, wedging, oligomerization, and crowding. The crowding effect in particular has received considerable attention recently, in part because it is a colligative mechanism-implying that it could, in principle, be explored by any peripheral protein. Here we sought to clarify to what extent this mechanism is exploited by endocytic accessory proteins. We quantitatively investigate membrane curvature generation by means of a GUV shape stability assay...
November 1, 2016: Biophysical Journal
Zhiming Chen, Chen Zhu, Curtis J Kuo, Jaclyn Robustelli, Tobias Baumgart
N-BAR proteins such as endophilin are thought to bend lipid membranes via scaffolding (the molding of membranes through the crescent protein shape) and membrane insertion (also called wedging) of amphipathic helices. However, the contributions from these distinct mechanisms to membrane curvature generation and sensing have remained controversial. Here we quantitatively demonstrate that the amphipathic N-terminal H0 helix of endophilin is important for recruiting this protein to the membrane, but does not contribute significantly to its intrinsic membrane curvature generation capacity...
November 9, 2016: Journal of the American Chemical Society
Qi Xiao, Jack D Rubien, Zhichun Wang, Ellen H Reed, Daniel A Hammer, Dipankar Sahoo, Paul A Heiney, Srujana S Yadavalli, Mark Goulian, Samantha E Wilner, Tobias Baumgart, Sergei A Vinogradov, Michael L Klein, Virgil Percec
The modular synthesis of a library containing seven self-assembling amphiphilic Janus dendrimers is reported. Three of these molecules contain environmentally friendly chiral-racemic fluorinated dendrons in their hydrophobic part (RF), one contains achiral hydrogenated dendrons (RH), while one denoted hybrid Janus dendrimer, contains a combination of chiral-racemic fluorinated and achiral hydrogenated dendrons (RHF) in its hydrophobic part. Two Janus dendrimers contain either chiral-racemic fluorinated dendrons and a green fluorescent dye conjugated to its hydrophilic part (RF-NBD) or achiral hydrogenated and a red fluorescent dye in its hydrophilic part (RH-RhB)...
September 28, 2016: Journal of the American Chemical Society
Xingfeng Liu, Jisen Huai, Heiko Endle, Leslie Schlüter, Wei Fan, Yunbo Li, Sebastian Richers, Hajime Yurugi, Krishnaraj Rajalingam, Haichao Ji, Hong Cheng, Benjamin Rister, Guilherme Horta, Jan Baumgart, Hendrik Berger, Gregor Laube, Ulrich Schmitt, Michael J Schmeisser, Tobias M Boeckers, Stefan Tenzer, Andreas Vlachos, Thomas Deller, Robert Nitsch, Johannes Vogt
Alterations in dendritic spine numbers are linked to deficits in learning and memory. While we previously revealed that postsynaptic plasticity-related gene 1 (PRG-1) controls lysophosphatidic acid (LPA) signaling at glutamatergic synapses via presynaptic LPA receptors, we now show that PRG-1 also affects spine density and synaptic plasticity in a cell-autonomous fashion via protein phosphatase 2A (PP2A)/β1-integrin activation. PRG-1 deficiency reduces spine numbers and β1-integrin activation, alters long-term potentiation (LTP), and impairs spatial memory...
August 8, 2016: Developmental Cell
Qingjie Luo, Zheng Shi, Yitao Zhang, Xi-Jun Chen, Seo-Yeon Han, Tobias Baumgart, David M Chenoweth, So-Jung Park
Here, we report DNA-induced polymer segregation and DNA island formation in binary block copolymer assemblies. A DNA diblock copolymer of polymethyl acrylate-block-DNA (PMA-b-DNA) and a triblock copolymer of poly(butadiene)-block-poly(ethylene oxide)-block-DNA (PBD-b-PEO-b-DNA) were synthesized, and each was coassembled with a prototypical amphiphilic polymer of poly(butadiene)-block-poly(ethylene oxide) (PBD-b-PEO). The binary self-assembly of PMA-b-DNA and PBD-b-PEO resulted in giant polymersomes with DNA uniformly distributed in the hydrophilic PEO shell...
August 17, 2016: Journal of the American Chemical Society
Richard W Tourdot, N Ramakrishnan, Tobias Baumgart, Ravi Radhakrishnan
This corrects the article DOI: 10.1103/PhysRevE.92.042715.
May 2016: Physical Review. E
Richard W Tourdot, N Ramakrishnan, Tobias Baumgart, Ravi Radhakrishnan
We investigate the phenomenon of protein-induced tubulation of lipid bilayer membranes within a continuum framework using Monte Carlo simulations coupled with the Widom insertion technique to compute excess chemical potentials. Tubular morphologies are spontaneously formed when the density and the curvature-field strength of the membrane-bound proteins exceed their respective thresholds and this transition is marked by a sharp drop in the excess chemical potential. We find that the planar to tubular transition can be described by a micellar model and that the corresponding free-energy barrier increases with an increase in the curvature-field strength (i...
October 2015: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
Zhiming Chen, Zheng Shi, Tobias Baumgart
I-BAR proteins are well-known actin-cytoskeleton adaptors and have been observed to be involved in the formation of plasma membrane protrusions (filopodia). I-BAR proteins contain an all-helical, crescent-shaped IRSp53-MIM domain (IMD) dimer that is believed to be able to couple with a membrane shape. This coupling could involve the sensing and even the generation of negative plasma membrane curvature. Indeed, the in vitro studies have shown that IMDs can induce inward tubulation of liposomes. While N-BAR domains, which generate positive membrane curvature, have received a considerable amount of attention from both theory and experiments, the mechanisms of curvature coupling through IMDs are comparatively less studied and understood...
July 21, 2015: Biophysical Journal
Zheng Shi, Jonathan N Sachs, Elizabeth Rhoades, Tobias Baumgart
α-Synuclein is an intrinsically disordered protein whose aggregation is a hallmark of Parkinson's disease. In neurons, α-synuclein is thought to play important roles in mediating both endo- and exocytosis of synaptic vesicles through interactions with either the lipid bilayer or other proteins. Upon membrane binding, the N-terminus of α-synuclein forms a helical structure and inserts into the hydrophobic region of the outer membrane leaflet. However, membrane structural changes induced by α-synuclein are still largely unclear...
June 28, 2015: Physical Chemistry Chemical Physics: PCCP
Zheng Shi, Tobias Baumgart
Endocytosis is a ubiquitous eukaryotic membrane budding, vesiculation and internalization process fulfilling numerous roles including compensation of membrane area increase after bursts of exocytosis. The mechanism of the coupling between these two processes to enable homeostasis is not well understood. Recently, an ultrafast endocytosis (UFE) pathway was revealed with a speed significantly exceeding classical clathrin-mediated endocytosis (CME). Membrane tension reduction is a potential mechanism by which endocytosis can be rapidly activated at remote sites...
2015: Nature Communications
Roland L Knorr, Hitoshi Nakatogawa, Yoshinori Ohsumi, Reinhard Lipowsky, Tobias Baumgart, Rumiana Dimova
Autophagy is a cellular degradation pathway involving the shape transformation of lipid bilayers. During the onset of autophagy, the water-soluble protein Atg8 binds covalently to phosphatdylethanolamines (PEs) in the membrane in an ubiquitin-like reaction coupled to ATP hydrolysis. We reconstituted the Atg8 conjugation system in giant and nm-sized vesicles with a minimal set of enzymes and observed that formation of Atg8-PE on giant vesicles can cause substantial tubulation of membranes even in the absence of Atg12-Atg5-Atg16...
2014: PloS One
Ute Distler, Michael J Schmeisser, Assunta Pelosi, Dominik Reim, Jörg Kuharev, Roland Weiczner, Jan Baumgart, Tobias M Boeckers, Robert Nitsch, Johannes Vogt, Stefan Tenzer
Located at neuronal terminals, the postsynaptic density (PSD) is a highly complex network of cytoskeletal scaffolding and signaling proteins responsible for the transduction and modulation of glutamatergic signaling between neurons. Using ion-mobility enhanced data-independent label-free LC-MS/MS, we established a reference proteome of crude synaptosomes, synaptic junctions, and PSD derived from mouse hippocampus including TOP3-based absolute quantification values for identified proteins. The final dataset across all fractions comprised 49 491 peptides corresponding to 4558 protein groups...
November 2014: Proteomics
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