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Alf Honigmann, A Pralle
Compartmentalization of the Cell Membrane.
J Mol Biol, 428(24 Pt A) 4739-4748 (2016)
PubMed   

Many cell-membrane-associated processes require transient spatiotemporal separation of components on scales ranging from a couple of molecules to micrometers in size. Understanding these processes mechanistically involves understanding how lipids and proteins self-organize and interact with the cell cortex. Here, we review recent advances in dissecting the mechanisms of cell membrane compartmentalization. We introduce the challenges in studying cell membrane organization, the current understanding of how complex membranes self-organize to form transient domains, and the role of protein scaffolds in membrane organization. We discuss the formation of signaling domains as an important example of transient membrane compartmentalization. We conclude by pointing to the current limitations of measuring membrane organization in living cells and the steps that are required to advance the field.
@article{Honigmann6708,
author={Alf Honigmann, A Pralle},
title={Compartmentalization of the Cell Membrane.},
journal={Journal of molecular biology},
volume={428},
issue ={24 Pt A},
pages={4739--4748},
year=2016
}

Ilaria Visco, Carsten Hoege, Anthony Hyman, Petra Schwille
In vitro Reconstitution of a Membrane Switch Mechanism for the Polarity Protein LGL.
J Mol Biol, 428(24 Pt A) 4828-4842 (2016)
PubMed   

Cell polarity arises from a combination of interactions between biological molecules, such as activation, inhibition, and positive or negative feedback between specific polarity units. Activation and inhibition often take place in the form of a membrane binding switch. Lethal giant larvae (LGL), a conserved regulator of cell polarity in animals, was suggested to function as such a switch. LGL localizes to both the cytoplasm and, asymmetrically, the membrane. However, the spatial regulation mechanism of LGL membrane localization has remained unclear. For systematic elucidation, we set out to reconstitute a minimal polarity unit using a model membrane, Caenorhabditis elegans LGL (LGL-1), and atypical protein kinase C (aPKC) supposed to activate the membrane switch. We identified a membrane binding sequence (MBS) in LGL-1 by a screen in vivo, reconstituted LGL-1 membrane binding in vitro, and successfully implemented the membrane switch by aPKC phosphorylation activity, detaching LGL from membranes. Upon membrane binding, LGL-1 MBS folds into an alpha-helix in which three regions can be identified: a positively charged patch, a switch area containing the three aPKC phosphorylation sites, and a hydrophobic area probably buried in the membrane. Phosphorylation by aPKC dramatically reduces the binding affinity of the LGL-1 MBS to negatively charged model membranes, inducing its detachment. Specific residues in the MBS are critical for LGL-1 function in C. elegans.
@article{Visco6706,
author={Ilaria Visco, Carsten Hoege, Anthony Hyman, Petra Schwille},
title={In vitro Reconstitution of a Membrane Switch Mechanism for the Polarity Protein LGL.},
journal={Journal of molecular biology},
volume={428},
issue ={24 Pt A},
pages={4828--4842},
year=2016
}

Jeffrey R Vieregg, T-Y Dora Tang
Polynucleotides in cellular mimics: Coacervates and lipid vesicles
Curr Opin Colloid Interface Sci, 26 50-57 (2016)
 

@article{Vieregg6679,
author={Jeffrey R Vieregg, T-Y Dora Tang},
title={Polynucleotides in cellular mimics: Coacervates and lipid vesicles},
journal={Current Opinion in Colloid & Interface Science},
volume={26},
pages={50--57},
year=2016
}

Linda Nemetschke, Elisabeth Knust
Drosophila Crumbs prevents ectopic Notch activation in developing wings by inhibiting ligand-independent endocytosis
Development, 143 4543-4553 (2016)
 

@article{Nemetschke6711,
author={Linda Nemetschke, Elisabeth Knust},
title={Drosophila Crumbs prevents ectopic Notch activation in developing wings by inhibiting ligand-independent endocytosis},
journal={Development (Cambridge, England)},
volume={143},
pages={4543--4553},
year=2016
}

Rahul Grover, Janine Fischer, Friedrich W Schwarz, Wilhelm Walter, Petra Schwille, Stefan Diez
Transport efficiency of membrane-anchored kinesin-1 motors depends on motor density and diffusivity.
Proc Natl Acad Sci U.S.A., 113(46) 7185-7193 (2016)
PubMed   

In eukaryotic cells, membranous vesicles and organelles are transported by ensembles of motor proteins. These motors, such as kinesin-1, have been well characterized in vitro as single molecules or as ensembles rigidly attached to nonbiological substrates. However, the collective transport by membrane-anchored motors, that is, motors attached to a fluid lipid bilayer, is poorly understood. Here, we investigate the influence of motors' anchorage to a lipid bilayer on the collective transport characteristics. We reconstituted "membrane-anchored" gliding motility assays using truncated kinesin-1 motors with a streptavidin-binding peptide tag that can attach to streptavidin-loaded, supported lipid bilayers. We found that the diffusing kinesin-1 motors propelled the microtubules in the presence of ATP. Notably, we found the gliding velocity of the microtubules to be strongly dependent on the number of motors and their diffusivity in the lipid bilayer. The microtubule gliding velocity increased with increasing motor density and membrane viscosity, reaching up to the stepping velocity of single motors. This finding is in contrast to conventional gliding motility assays where the density of surface-immobilized kinesin-1 motors does not influence the microtubule velocity over a wide range. We reason that the transport efficiency of membrane-anchored motors is reduced because of their slippage in the lipid bilayer, an effect that we directly observed using single-molecule fluorescence microscopy. Our results illustrate the importance of motor-cargo coupling, which potentially provides cells with an additional means of regulating the efficiency of cargo transport.
@article{Grover6710,
author={Rahul Grover, Janine Fischer, Friedrich W Schwarz, Wilhelm Walter, Petra Schwille, Stefan Diez},
title={Transport efficiency of membrane-anchored kinesin-1 motors depends on motor density and diffusivity.},
journal={Proceedings of the National Academy of Sciences of the United States of America},
volume={113},
issue ={46},
pages={7185--7193},
year=2016
}

Cordula Reuther, Alejandra Laguillo Diego, Stefan Diez
Kinesin-1 motors can increase the lifetime of taxol-stabilized microtubules.
Nat Nanotechnol, 11(11) 914-915 (2016)
PubMed  

@article{Reuther6698,
author={Cordula Reuther, Alejandra Laguillo Diego, Stefan Diez},
title={Kinesin-1 motors can increase the lifetime of taxol-stabilized microtubules.},
journal={Nature nanotechnology},
volume={11},
issue ={11},
pages={914--915},
year=2016
}

Maksim V Baranov, Natalia H Revelo, Ilse Dingjan, Riccardo Maraspini, Martin Ter Beest, Alf Honigmann, Geert van den Bogaart
SWAP70 Organizes the Actin Cytoskeleton and Is Essential for Phagocytosis.
Cell Rep, 17(6) 1518-1531 (2016)
  PubMed   

Actin plays a critical role during the early stages of pathogenic microbe internalization by immune cells. In this study, we identified a key mechanism of actin filament tethering and stabilization to the surface of phagosomes in human dendritic cells. We found that the actin-binding protein SWAP70 is specifically recruited to nascent phagosomes by binding to the lipid phosphatidylinositol (3,4)-bisphosphate. Multi-color super-resolution stimulated emission depletion (STED) microscopy revealed that the actin cage surrounding early phagosomes is formed by multiple concentric rings containing SWAP70. SWAP70 colocalized with and stimulated activation of RAC1, a known activator of actin polymerization, on phagosomes. Genetic ablation of SWAP70 impaired actin polymerization around phagosomes and resulted in a phagocytic defect. These data show a key role for SWAP70 as a scaffold for tethering the peripheral actin cage to phagosomes.
@article{Baranov6695,
author={Maksim V Baranov, Natalia H Revelo, Ilse Dingjan, Riccardo Maraspini, Martin Ter Beest, Alf Honigmann, Geert van den Bogaart},
title={SWAP70 Organizes the Actin Cytoskeleton and Is Essential for Phagocytosis.},
journal={Cell reports},
volume={17},
issue ={6},
pages={1518--1531},
year=2016
}

Mariola R. Chacón, Petrina Delivani, Iva M Tolić
Meiotic Nuclear Oscillations Are Necessary to Avoid Excessive Chromosome Associations.
Cell Rep, 17(6) 1632-1645 (2016)
  PubMed   

Pairing of homologous chromosomes is a crucial step in meiosis, which in fission yeast depends on nuclear oscillations. However, how nuclear oscillations help pairing is unknown. Here, we show that homologous loci typically pair when the spindle pole body is at the cell pole and the nucleus is elongated, whereas they unpair when the spindle pole body is in the cell center and the nucleus is round. Inhibition of oscillations demonstrated that movement is required for initial pairing and that prolonged association of loci leads to mis-segregation. The double-strand break marker Rec25 accumulates in elongated nuclei, indicating that prolonged chromosome stretching triggers recombinatory pathways leading to mis-segregation. Mis-segregation is rescued by overexpression of the Holliday junction resolvase Mus81, suggesting that prolonged pairing results in irresolvable recombination intermediates. We conclude that nuclear oscillations exhibit a dual role, promoting initial pairing and restricting the time of chromosome associations to ensure proper segregation.
@article{Chacón6696,
author={Mariola R. Chacón, Petrina Delivani, Iva M Tolić},
title={Meiotic Nuclear Oscillations Are Necessary to Avoid Excessive Chromosome Associations.},
journal={Cell reports},
volume={17},
issue ={6},
pages={1632--1645},
year=2016
}

Peter Horvath, Nathalie Aulner, Marc Bickle, Anthony M Davies, Elaine Del Nery, Daniel Ebner, Maria Montoya, Päivi Östling, Vilja Pietiäinen, Leo S Price, Spencer L Shorte, Gerardo Turcatti, Carina von Schantz, Neil O Carragher
Screening out irrelevant cell-based models of disease.
Nat Rev Drug Discov, 15(11) 751-769 (2016)
PubMed   

The common and persistent failures to translate promising preclinical drug candidates into clinical success highlight the limited effectiveness of disease models currently used in drug discovery. An apparent reluctance to explore and adopt alternative cell- and tissue-based model systems, coupled with a detachment from clinical practice during assay validation, contributes to ineffective translational research. To help address these issues and stimulate debate, here we propose a set of principles to facilitate the definition and development of disease-relevant assays, and we discuss new opportunities for exploiting the latest advances in cell-based assay technologies in drug discovery, including induced pluripotent stem cells, three-dimensional (3D) co-culture and organ-on-a-chip systems, complemented by advances in single-cell imaging and gene editing technologies. Funding to support precompetitive, multidisciplinary collaborations to develop novel preclinical models and cell-based screening technologies could have a key role in improving their clinical relevance, and ultimately increase clinical success rates.
@article{Horvath6692,
author={Peter Horvath, Nathalie Aulner, Marc Bickle, Anthony M Davies, Elaine Del Nery, Daniel Ebner, Maria Montoya, Päivi Östling, Vilja Pietiäinen, Leo S Price, Spencer L Shorte, Gerardo Turcatti, Carina von Schantz, Neil O Carragher},
title={Screening out irrelevant cell-based models of disease.},
journal={Nature reviews. Drug discovery},
volume={15},
issue ={11},
pages={751--769},
year=2016
}

Loic Royer, William Lemon, Raghav K Chhetri, Yinan Wan, Michael Coleman, Eugene W Myers, Patrick Keller
Adaptive light-sheet microscopy for long-term, high-resolution imaging in living organisms.
Nat Biotechnol, Art. No. doi:10.1038/nbt.3708 (2016)
PubMed   

Optimal image quality in light-sheet microscopy requires a perfect overlap between the illuminating light sheet and the focal plane of the detection objective. However, mismatches between the light-sheet and detection planes are common owing to the spatiotemporally varying optical properties of living specimens. Here we present the AutoPilot framework, an automated method for spatiotemporally adaptive imaging that integrates (i) a multi-view light-sheet microscope capable of digitally translating and rotating light-sheet and detection planes in three dimensions and (ii) a computational method that continuously optimizes spatial resolution across the specimen volume in real time. We demonstrate long-term adaptive imaging of entire developing zebrafish (Danio rerio) and Drosophila melanogaster embryos and perform adaptive whole-brain functional imaging in larval zebrafish. Our method improves spatial resolution and signal strength two to five-fold, recovers cellular and sub-cellular structures in many regions that are not resolved by non-adaptive imaging, adapts to spatiotemporal dynamics of genetically encoded fluorescent markers and robustly optimizes imaging performance during large-scale morphogenetic changes in living organisms.
@article{Royer6701,
author={Loic Royer, William Lemon, Raghav K Chhetri, Yinan Wan, Michael Coleman, Eugene W Myers, Patrick Keller},
title={Adaptive light-sheet microscopy for long-term, high-resolution imaging in living organisms.},
journal={Nature biotechnology},
volume={},
pages={null--null},
year=2016
}