10 results on '"Robin W. Klemm"'
Search Results
2. Adipocyte-like signature in ovarian cancer minimal residual disease identifies metabolic vulnerabilities of tumor initiating cells
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P N Pathiraja, Nina Wietek, Robin W. Klemm, Matteo Morotti, Kay Chong, Christer S. Ejsing, S Nicum, Fergus V. Gleeson, Christos E. Zois, Zhimin Lu, Robert C. Bast, Kenta Masuda, Stephen Damato, P C Rauher, Christopher Yau, Alexandros Laios, Zhiyuan Hu, Abdulkhaliq Alsaadi, Garry Mallett, L Santana Gonzalez, Takeshi Motohara, Salma El-Sahhar, Leticia Campo, Sunanda Dhar, Adrian L. Harris, Mohammad KaramiNejadRanjbar, Ahmed Ashour Ahmed, Ashwag Albukhari, Sarah P. Blagden, Tatjana Sauka-Spengler, and Mara Artibani
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0301 basic medicine ,Epithelial-Mesenchymal Transition ,Neoplasm, Residual ,Paclitaxel ,medicine.medical_treatment ,Obstetrics/gynecology ,Carcinoma, Ovarian Epithelial ,Carboplatin ,Transcriptome ,03 medical and health sciences ,0302 clinical medicine ,Cell Line, Tumor ,hemic and lymphatic diseases ,Antineoplastic Combined Chemotherapy Protocols ,Gene expression ,Adipocytes ,medicine ,Humans ,Cytotoxicity ,Aged ,Aged, 80 and over ,Ovarian Neoplasms ,Chemotherapy ,business.industry ,Fatty Acids ,Cytoreduction Surgical Procedures ,General Medicine ,Middle Aged ,medicine.disease ,Phenotype ,Minimal residual disease ,Neoadjuvant Therapy ,body regions ,030104 developmental biology ,Oncology ,Cell culture ,Fatty acid oxidation ,030220 oncology & carcinogenesis ,Neoplastic Stem Cells ,Cancer research ,Female ,Ovarian cancer ,business ,Oxidation-Reduction ,Research Article - Abstract
Similar to tumor-initiating cells (TICs), minimal residual disease (MRD) is capable of reinitiating tumors and causing recurrence. However, the molecular characteristics of solid tumor MRD cells and drivers of their survival have remained elusive. Here we performed dense multiregion transcriptomics analysis of paired biopsies from 17 ovarian cancer patients before and after chemotherapy. We reveal that while MRD cells share important molecular signatures with TICs, they are also characterized by an adipocyte-like gene expression signature and a portion of them had undergone epithelial-mesenchymal transition (EMT). In a cell culture MRD model, MRD-mimic cells showed the same phenotype and were dependent on fatty acid oxidation (FAO) for survival and resistance to cytotoxic agents. These findings identify EMT and FAO as attractive targets to eradicate MRD in ovarian cancer and make a compelling case for the further testing of FAO inhibitors in treating MRD.
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- 2021
3. MIGA2 Links Mitochondria, the ER, and Lipid Droplets and Promotes De Novo Lipogenesis in Adipocytes
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Robin W. Klemm, Christophe A.C. Freyre, Christer S. Ejsing, Pascal C. Rauher, University of Zurich, and Klemm, Robin W
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Cell type ,Vesicular Transport Proteins ,Mitochondrion ,Biology ,Endoplasmic Reticulum ,Energy homeostasis ,1307 Cell Biology ,Mitochondrial Proteins ,03 medical and health sciences ,Mice ,0302 clinical medicine ,Lipid droplet ,Organelle ,Chlorocebus aethiops ,1312 Molecular Biology ,Adipocytes ,Animals ,Humans ,Molecular Biology ,adipocyte differentiation ,Triglycerides ,030304 developmental biology ,0303 health sciences ,Endoplasmic reticulum ,Lipogenesis ,mass spectrometry lipidomics ,Membrane Proteins ,Cell Differentiation ,lipid droplet expansion ,Cell Biology ,3T3 Cells ,Lipid Droplets ,10124 Institute of Molecular Life Sciences ,Cell biology ,Mitochondria ,HEK293 Cells ,organelle contact sites ,Membrane protein ,COS Cells ,transcriptomics of adipocyte differentiation ,570 Life sciences ,biology ,030217 neurology & neurosurgery - Abstract
Physical contact between organelles is vital to the function of eukaryotic cells. Lipid droplets (LDs) are dynamic organelles specialized in lipid storage that interact physically with mitochondria in several cell types. The mechanisms coupling these organelles are, however, poorly understood, and the cell-biological function of their interaction remains largely unknown. Here, we discover in adipocytes that the outer mitochondrial membrane protein MIGA2 links mitochondria to LDs. We identify an amphipathic LD-targeting motif and reveal that MIGA2 binds to the membrane proteins VAP-A or VAP-B in the endoplasmic reticulum (ER). We find that in adipocytes MIGA2 is involved in promoting triglyceride (TAG) synthesis from non-lipid precursors. Our data indicate that MIGA2 links reactions of de novo lipogenesis in mitochondria to TAG production in the ER, thereby facilitating efficient lipid storage in LDs. Based on its presence in many tissues, MIGA2 is likely critical for lipid and energy homeostasis in a wide spectrum of cell types.
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- 2019
4. ER remodeling by the large GTPase atlastin promotes vacuolar growth of
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Bernhard, Steiner, Anna Leoni, Swart, Amanda, Welin, Stephen, Weber, Nicolas, Personnic, Andres, Kaech, Christophe, Freyre, Urs, Ziegler, Robin W, Klemm, and Hubert, Hilbi
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Proteomics ,Type IV Secretion Systems ,A549 Cells ,GTP-Binding Proteins ,Macrophages ,Nogo Proteins ,Vacuoles ,Humans ,Membrane Proteins ,Dictyostelium ,Articles ,Endoplasmic Reticulum ,Legionella pneumophila - Abstract
The pathogenic bacterium Legionella pneumophila replicates in host cells within a distinct ER‐associated compartment termed the Legionella‐containing vacuole (LCV). How the dynamic ER network contributes to pathogen proliferation within the nascent LCV remains elusive. A proteomic analysis of purified LCVs identified the ER tubule‐resident large GTPase atlastin3 (Atl3, yeast Sey1p) and the reticulon protein Rtn4 as conserved LCV host components. Here, we report that Sey1/Atl3 and Rtn4 localize to early LCVs and are critical for pathogen vacuole formation. Sey1 overproduction promotes intracellular growth of L. pneumophila, whereas a catalytically inactive, dominant‐negative GTPase mutant protein, or Atl3 depletion, restricts pathogen replication and impairs LCV maturation. Sey1 is not required for initial recruitment of ER to PtdIns(4)P‐positive LCVs but for subsequent pathogen vacuole expansion. GTP (but not GDP) catalyzes the Sey1‐dependent aggregation of purified, ER‐positive LCVs in vitro. Thus, Sey1/Atl3‐dependent ER remodeling contributes to LCV maturation and intracellular replication of L. pneumophila.
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- 2017
5. A model for the generation and interconversion of ER morphologies
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Joshua C. Vaughan, Michael M. Kozlov, Tom A. Rapoport, Shengyin Wang, Tom Shemesh, Xiaowei Zhuang, Hanna Tukachinsky, Fabian B. Romano, and Robin W. Klemm
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Time Factors ,Peripheral endoplasmic reticulum ,Protein Conformation ,Biology ,Endoplasmic Reticulum ,Models, Biological ,Xenopus laevis ,Protein structure ,Imaging, Three-Dimensional ,Chlorocebus aethiops ,Animals ,Humans ,Homeodomain Proteins ,Multidisciplinary ,Endoplasmic reticulum ,Membrane Proteins ,Elasticity ,Cell biology ,Membrane ,HEK293 Cells ,Membrane protein ,Microscopy, Fluorescence ,PNAS Plus ,Membrane curvature ,Reticulon ,COS Cells ,Biophysics ,RNA Interference - Abstract
The peripheral endoplasmic reticulum (ER) forms different morphologies composed of tubules and sheets. Proteins such as the reticulons shape the ER by stabilizing the high membrane curvature in cross-sections of tubules and sheet edges. Here, we show that membrane curvature along the edge lines is also critical for ER shaping. We describe a theoretical model that explains virtually all observed ER morphologies. The model is based on two types of curvature-stabilizing proteins that generate either straight or negatively curved edge lines (R- and S-type proteins). Dependent on the concentrations of R- and S-type proteins, membrane morphologies can be generated that consist of tubules, sheets, sheet fenestrations, and sheet stacks with helicoidal connections. We propose that reticulons 4a/b are representatives of R-type proteins that favor tubules and outer edges of sheets. Lunapark is an example of S-type proteins that promote junctions between tubules and sheets. In a tubular ER network, lunapark stabilizes three-way junctions, i.e., small triangular sheets with concave edges. The model agrees with experimental observations and explains how curvature-stabilizing proteins determine ER morphology.
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- 2014
6. A conserved role for atlastin GTPases in regulating lipid droplet size
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Tina Y. Liu, Liying Li, Seong H. Park, Justin P. Norton, Matthew M. Crane, Chen S. Li, Craig Blackstone, Tom A. Rapoport, Alexandra Boye-Doe, Hang Lu, Robin W. Klemm, Diana Jin, Robert V. Farese, Yoko Shibata, Ho Yi Mak, Ronald A. Cole, and Yi Guo
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Atlastin ,GTPase ,Biology ,Endoplasmic Reticulum ,General Biochemistry, Genetics and Molecular Biology ,Article ,GTP Phosphohydrolases ,03 medical and health sciences ,0302 clinical medicine ,GTP-binding protein regulators ,GTP-Binding Proteins ,Lipid droplet ,Organelle ,Chlorocebus aethiops ,Animals ,Humans ,RNA, Small Interfering ,Caenorhabditis elegans ,Caenorhabditis elegans Proteins ,lcsh:QH301-705.5 ,030304 developmental biology ,0303 health sciences ,Endoplasmic reticulum ,Cytoplasmic Vesicles ,Lipid bilayer fusion ,Membrane Proteins ,Membrane Transport Proteins ,Cell biology ,lcsh:Biology (General) ,Membrane protein ,COS Cells ,Mutation ,Drosophila ,RNA Interference ,030217 neurology & neurosurgery - Abstract
SummaryLipid droplets (LDs) are the major fat storage organelles in eukaryotic cells, but how their size is regulated is unknown. Using genetic screens in C. elegans for LD morphology defects in intestinal cells, we found that mutations in atlastin, a GTPase required for homotypic fusion of endoplasmic reticulum (ER) membranes, cause not only ER morphology defects, but also a reduction in LD size. Similar results were obtained after depletion of atlastin or expression of a dominant-negative mutant, whereas overexpression of atlastin had the opposite effect. Atlastin depletion in Drosophila fat bodies also reduced LD size and decreased triglycerides in whole animals, sensitizing them to starvation. In mammalian cells, co-overexpression of atlastin-1 and REEP1, a paralog of the ER tubule-shaping protein DP1/REEP5, generates large LDs. The effect of atlastin-1 on LD size correlates with its activity to promote membrane fusion in vitro. Our results indicate that atlastin-mediated fusion of ER membranes is important for LD size regulation.
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- 2012
7. A genomic toolkit to investigate kinesin and myosin motor function in cells
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Andrej Shevchenko, Andreas Ettinger, Anthony A. Hyman, Yusuke Toyoda, Andrej Vasilj, Magno Junqueira, Ina Poser, Elaine Guhr, Itziar Ibarlucea-Benitez, Wieland B. Huttner, Ezio Bonifacio, Felipe Mora-Bermúdez, Robin W. Klemm, and Zoltan Maliga
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Chromosomes, Artificial, Bacterial ,Fluorescent Antibody Technique ,Kinesins ,Microtubules ,Chromatography, Affinity ,Mice ,Neuroblastoma ,0302 clinical medicine ,Cell Movement ,Myosin ,Transgenes ,Phylogeny ,Oligonucleotide Array Sequence Analysis ,Neurons ,0303 health sciences ,Reverse Transcriptase Polymerase Chain Reaction ,Stem Cells ,Transfection ,Genomics ,Cell biology ,Kinesin ,Microtubule-Associated Proteins ,Blotting, Western ,Green Fluorescent Proteins ,Mitosis ,Mice, Transgenic ,Biology ,Myosins ,Real-Time Polymerase Chain Reaction ,Motor protein ,03 medical and health sciences ,Microtubule ,Animals ,Humans ,Immunoprecipitation ,RNA, Messenger ,Embryonic Stem Cells ,030304 developmental biology ,Centrosome ,Gene Expression Profiling ,Biological Transport ,Cell Biology ,Phosphoproteins ,Cell culture ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Protein Multimerization ,030217 neurology & neurosurgery ,Biomarkers ,HeLa Cells - Abstract
Coordination of multiple kinesin and myosin motors is required for intracellular transport, cell motility and mitosis. However, comprehensive resources that allow systems analysis of the localization and interplay between motors in living cells do not exist. Here, we generated a library of 243 amino- and carboxy-terminally tagged mouse and human bacterial artificial chromosome transgenes to establish 227 stably transfected HeLa cell lines, 15 mouse embryonic stem cell lines and 1 transgenic mouse line. The cells were characterized by expression and localization analyses and further investigated by affinity-purification mass spectrometry, identifying 191 candidate protein-protein interactions. We illustrate the power of this resource in two ways. First, by characterizing a network of interactions that targets CEP170 to centrosomes, and second, by showing that kinesin light-chain heterodimers bind conventional kinesin in cells. Our work provides a set of validated resources and candidate molecular pathways to investigate motor protein function across cell lineages.
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- 2012
8. Lipid interaction of the C terminus and association of the transmembrane segments facilitate atlastin-mediated homotypic endoplasmic reticulum fusion
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Robin W. Klemm, Tina Y. Liu, Sha Sun, Tom A. Rapoport, Xin Bian, Junjie Hu, William A. Prinz, and Xiaoyu Hu
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Models, Molecular ,Atlastin ,Vesicle fusion ,Molecular Sequence Data ,GTPase ,Biology ,Endoplasmic Reticulum ,Membrane Fusion ,GTP Phosphohydrolases ,Species Specificity ,Yeasts ,Escherichia coli ,Fluorescence Resonance Energy Transfer ,Animals ,Drosophila Proteins ,Humans ,Immunoprecipitation ,Amino Acid Sequence ,Lipid bilayer ,Multidisciplinary ,Circular Dichroism ,C-terminus ,Endoplasmic reticulum ,Lipid bilayer fusion ,Fluoresceins ,Lipid Metabolism ,Transmembrane protein ,Cell biology ,Drosophila melanogaster ,Gene Components ,PNAS Plus ,Microscopy, Fluorescence ,Biochemistry ,Liposomes ,Electrophoresis, Polyacrylamide Gel - Abstract
The homotypic fusion of endoplasmic reticulum (ER) membranes is mediated by atlastin (ATL), which consists of an N-terminal cytosolic domain containing a GTPase module and a three-helix bundle followed by two transmembrane (TM) segments and a C-terminal tail (CT). Fusion depends on a GTP hydrolysis-induced conformational change in the cytosolic domain. Here, we show that the CT and TM segments also are required for efficient fusion and provide insight into their mechanistic roles. The essential feature of the CT is a conserved amphipathic helix. A synthetic peptide corresponding to the helix, but not to unrelated amphipathic helices, can act in trans to restore the fusion activity of tailless ATL. The CT promotes vesicle fusion by interacting directly with and perturbing the lipid bilayer without causing significant lysis. The TM segments do not serve as mere membrane anchors for the cytosolic domain but rather mediate the formation of ATL oligomers. Point mutations in either the C-terminal helix or the TMs impair ATL’s ability to generate and maintain ER morphology in vivo. Our results suggest that protein–lipid and protein–protein interactions within the membrane cooperate with the conformational change of the cytosolic domain to achieve homotypic ER membrane fusion.
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- 2012
9. Molecular Convergence of Bacterial and Eukaryotic Surface Order*
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Daniel Lingwood, Chris Meisinger, Kai Simons, Michal A. Surma, Michał Grzybek, Sandrine Da Cruz, Florian Mayer, Ilya Levental, Robin W. Klemm, Volker Müller, and Hermann Josef Kaiser
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Membrane lipids ,Lipid Bilayers ,Molecular Sequence Data ,Biology ,Biochemistry ,Cell membrane ,Bacterial Proteins ,medicine ,Animals ,Humans ,Amino Acid Sequence ,Lipid bilayer ,Molecular Biology ,Bacteria ,Cell Membrane ,Eukaryota ,Membrane Proteins ,Biological membrane ,Cell Biology ,Transmembrane protein ,Peptide Fragments ,Rats ,Membrane ,medicine.anatomical_structure ,Membrane biogenesis ,lipids (amino acids, peptides, and proteins) ,Membrane biophysics ,Molecular Biophysics - Abstract
The conservation of fluidity is a theme common to all cell membranes. In this study, an analysis of lipid packing was conducted via C-laurdan spectroscopy of cell surface membranes prepared from representative species of Bacteria and Eukarya. We found that despite their radical differences in composition (namely the presence and absence of membrane-rigidifying sterol) the membrane order of all taxa converges on a remarkably similar level. To understand how this similarity is constructed, we reconstituted membranes with either bacterial or eukaryotic components. We found that transmembrane segments of proteins have an important role in buffering lipid-mediated packing. This buffering ensures that sterol-free and sterol-containing membranes exhibit similar barrier properties.
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- 2011
10. Structures of the atlastin GTPase provide insight into homotypic fusion of endoplasmic reticulum membranes
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Sha Sun, Xinqi Liu, Xin Bian, Xuewu Sui, Robin W. Klemm, Miao Zhang, Junjie Hu, Tom A. Rapoport, and Tina Y. Liu
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Atlastin ,Models, Molecular ,Multidisciplinary ,Protein Conformation ,Endoplasmic reticulum ,Hydrolysis ,Lipid bilayer fusion ,Membrane Proteins ,GTPase ,Biology ,Biological Sciences ,Endoplasmic Reticulum ,Membrane Fusion ,Transmembrane protein ,Cell biology ,GTP Phosphohydrolases ,GTP-binding protein regulators ,Membrane protein ,GTP-Binding Proteins ,Mutation ,Humans ,Guanosine Triphosphate ,Dimerization ,Fusion mechanism - Abstract
The generation of the tubular network of the endoplasmic reticulum (ER) requires homotypic membrane fusion that is mediated by the dynamin-like, membrane-bound GTPase atlastin (ATL). Here, we have determined crystal structures of the cytosolic segment of human ATL1, which give insight into the mechanism of membrane fusion. The structures reveal a GTPase domain and athree-helix bundle, connected by a linker region. One structure corresponds to a prefusion state, in which ATL molecules in apposing membranes interact through their GTPase domains to form a dimer with the nucleotides bound at the interface. The other structure corresponds to a postfusion state generated after GTP hydrolysis and phosphate release. Compared with the prefusion structure, the three-helix bundles of the two ATL molecules undergo a major conformational change relative to the GTPase domains, which could pull the membranes together. The proposed fusion mechanism is supported by biochemical experiments and fusion assays with wild-type and mutant full-length Drosophila ATL. These experiments also show that membrane fusion is facilitated by the C-terminal cytosolic tails following the two transmembrane segments. Finally, our results show that mutations in ATL1 causing hereditary spastic paraplegia compromise homotypic ER fusion.
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- 2011
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