GTP-tubulin loves microtubule plus ends but marries the minus ends
Microtubule minus ends are inherently more stable than plus ends despite the fact that free tubulin associates more avidly to the plus end. In this issue, Strothman et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201905019) measure, for the first time, the off-rate for GTP-tubulin and find that it is different for the two ends, suggesting that this parameter may control the transition to disassembly at microtubule ends. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Wordeman, L. Tags: Cytoskeleton, Cell Cycle and Division, Biochemistry, Cancer Spotlight Source Type: research
Early Career Advisory Board: Q&A on career and publishing
We interviewed our Early Career Advisory Board to learn about their experiences finding their academic position and managing a new laboratory, and their views on peer review and scientific publishing. An excerpted version is presented here and all other responses are found in the supplemental material. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Marat, A. Tags: People & amp;amp; Ideas Source Type: research
Suzanne Eaton (1959-2019): A pioneer in quantitative tissue morphogenesis
Multa novit vulpes, verum echinus unum magnum ("A fox knows many things, but a hedgehog one important thing"). This proverb was written on a poster plastered to the door of Suzanne Eaton’s laboratory, together with a drawing she made... (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Knust, E., Simons, K. Tags: In Memoriam Source Type: research
High-throughput ultrastructure screening using electron microscopy and fluorescent barcoding
Genetic screens using high-throughput fluorescent microscopes have generated large datasets, contributing many cell biological insights. Such approaches cannot tackle questions requiring knowledge of ultrastructure below the resolution limit of fluorescent microscopy. Electron microscopy (EM) reveals detailed cellular ultrastructure but requires time-consuming sample preparation, limiting throughput. Here we describe a robust method for screening by high-throughput EM. Our approach uses combinations of fluorophores as barcodes to uniquely mark each cell type in mixed populations and correlative light and EM (CLEM) to read ...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Bykov, Y. S., Cohen, N., Gabrielli, N., Manenschijn, H., Welsch, S., Chlanda, P., Kukulski, W., Patil, K. R., Schuldiner, M., Briggs, J. A. G. Tags: Organelles, Membrane and Lipid Biology, Biophysics, Technology Tools Source Type: research
Quantitative glycoproteomics reveals new classes of STT3A- and STT3B-dependent N-glycosylation sites
Human cells express two oligosaccharyltransferase complexes (STT3A and STT3B) with partially overlapping functions. The STT3A complex interacts directly with the protein translocation channel to mediate cotranslational glycosylation, while the STT3B complex can catalyze posttranslocational glycosylation. We used a quantitative glycoproteomics procedure to compare glycosylation of roughly 1,000 acceptor sites in wild type and mutant cells. Analysis of site occupancy data disclosed several new classes of STT3A-dependent acceptor sites including those with suboptimal flanking sequences and sites located within cysteine-rich p...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Cherepanova, N. A., Venev, S. V., Leszyk, J. D., Shaffer, S. A., Gilmore, R. Tags: Protein Homeostasis, Biochemistry Tools Source Type: research
Yorkie controls tube length and apical barrier integrity during airway development
Epithelial organ size and shape depend on cell shape changes, cell–matrix communication, and apical membrane growth. The Drosophila melanogaster embryonic tracheal network is an excellent model to study these processes. Here, we show that the transcriptional coactivator of the Hippo pathway, Yorkie (YAP/TAZ in vertebrates), plays distinct roles in the developing Drosophila airways. Yorkie exerts a cytoplasmic function by binding Drosophila Twinstar, the orthologue of the vertebrate actin-severing protein Cofilin, to regulate F-actin levels and apical cell membrane size, which are required for proper tracheal tube elo...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Skouloudaki, K., Christodoulou, I., Khalili, D., Tsarouhas, V., Samakovlis, C., Tomancak, P., Knust, E., Papadopoulos, D. K. Tags: Cytoskeleton, Polarity, Biophysics, Development Articles Source Type: research
Cross-linker-mediated regulation of actin network organization controls tissue morphogenesis
Contraction of cortical actomyosin networks driven by myosin activation controls cell shape changes and tissue morphogenesis during animal development. In vitro studies suggest that contractility also depends on the geometrical organization of actin filaments. Here we analyze the function of actomyosin network topology in vivo using optogenetic stimulation of myosin-II in Drosophila embryos. We show that early during cellularization, hexagonally arrayed actomyosin fibers are resilient to myosin-II activation. Actomyosin fibers then acquire a ring-like conformation and become contractile and sensitive to myosin-II. This tra...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Krueger, D., Quinkler, T., Mortensen, S. A., Sachse, C., De Renzis, S. Tags: Cytoskeleton, Development Articles Source Type: research
Microtubules promote intercellular contractile force transmission during tissue folding
During development, forces transmitted between cells are critical for sculpting epithelial tissues. Actomyosin contractility in the middle of the cell apex (medioapical) can change cell shape (e.g., apical constriction) but can also result in force transmission between cells via attachments to adherens junctions. How actomyosin networks maintain attachments to adherens junctions under tension is poorly understood. Here, we discovered that microtubules promote actomyosin intercellular attachments in epithelia during Drosophila melanogaster mesoderm invagination. First, we used live imaging to show a novel arrangement of the...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Ko, C. S., Tserunyan, V., Martin, A. C. Tags: Cytoskeleton, Polarity, Development Articles Source Type: research
SGEF forms a complex with Scribble and Dlg1 and regulates epithelial junctions and contractility
The canonical Scribble polarity complex is implicated in regulation of epithelial junctions and apical polarity. Here, we show that SGEF, a RhoG-specific GEF, forms a ternary complex with Scribble and Dlg1, two members of the Scribble complex. SGEF targets to apical junctions in a Scribble-dependent fashion and functions in the regulation of actomyosin-based contractility and barrier function at tight junctions as well as E-cadherin–mediated formation of adherens junctions. Surprisingly, SGEF does not control the establishment of polarity. However, in 3D cysts, SGEF regulates the formation of a single open lumen. Int...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Awadia, S., Huq, F., Arnold, T. R., Goicoechea, S. M., Sun, Y. J., Hou, T., Kreider-Letterman, G., Massimi, P., Banks, L., Fuentes, E. J., Miller, A. L., Garcia-Mata, R. Tags: Adhesion, Polarity, Biochemistry Articles Source Type: research
Synaptic neurexin-1 assembles into dynamically regulated active zone nanoclusters
Neurexins are well-characterized presynaptic cell adhesion molecules that engage multifarious postsynaptic ligands and organize diverse synapse properties. However, the precise synaptic localization of neurexins remains enigmatic. Using super-resolution microscopy, we demonstrate that neurexin-1 forms discrete nanoclusters at excitatory synapses, revealing a novel organizational feature of synaptic architecture. Synapses generally contain a single nanocluster that comprises more than four neurexin-1 molecules and that also includes neurexin-2 and/or neurexin-3 isoforms. Moreover, we find that neurexin-1 is physiologically ...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Trotter, J. H., Hao, J., Maxeiner, S., Tsetsenis, T., Liu, Z., Zhuang, X., Südhof, T. C. Tags: Adhesion, Trafficking, Neuroscience Articles Source Type: research
Developmentally regulated GTP-binding protein 1 modulates ciliogenesis via an interaction with Dishevelled
Cilia are critical for proper embryonic development and maintaining homeostasis. Although extensively studied, there are still significant gaps regarding the proteins involved in regulating ciliogenesis. Using the Xenopus laevis embryo, we show that Dishevelled (Dvl), a key Wnt signaling scaffold that is critical to proper ciliogenesis, interacts with Drg1 (developmentally regulated GTP-binding protein 1). The loss of Drg1 or disruption of the interaction with Dvl reduces the length and number of cilia and displays defects in basal body migration and docking to the apical surface of multiciliated cells (MCCs). Moreover, Dr...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Lee, M., Hwang, Y.-S., Yoon, J., Sun, J., Harned, A., Nagashima, K., Daar, I. O. Tags: Cilia, Development Articles Source Type: research
Maize defective kernel5 is a bacterial TamB homologue required for chloroplast envelope biogenesis
Chloroplasts are of prokaryotic origin with a double-membrane envelope separating plastid metabolism from the cytosol. Envelope membrane proteins integrate chloroplasts with the cell, but envelope biogenesis mechanisms remain elusive. We show that maize defective kernel5 (dek5) is critical for envelope biogenesis. Amyloplasts and chloroplasts are larger and reduced in number in dek5 with multiple ultrastructural defects. The DEK5 protein is homologous to rice SSG4, Arabidopsis thaliana EMB2410/TIC236, and Escherichia coli tamB. TamB functions in bacterial outer membrane biogenesis. DEK5 is localized to the envelope with a ...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Zhang, J., Wu, S., Boehlein, S. K., McCarty, D. R., Song, G., Walley, J. W., Myers, A., Settles, A. M. Tags: Organelles, Membrane and Lipid Biology, Genetics, Plant Biology Articles Source Type: research
The amino acid transporter SLC-36.1 cooperates with PtdIns3P 5-kinase to control phagocytic lysosome reformation
Phagocytic removal of apoptotic cells involves formation, maturation, and digestion of cell corpse–containing phagosomes. The retrieval of lysosomal components following phagolysosomal digestion of cell corpses remains poorly understood. Here we reveal that the amino acid transporter SLC-36.1 is essential for lysosome reformation during cell corpse clearance in Caenorhabditis elegans embryos. Loss of slc-36.1 leads to formation of phagolysosomal vacuoles arising from cell corpse–containing phagosomes. In the absence of slc-36.1, phagosome maturation is not affected, but the retrieval of lysosomal components is ...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Gan, Q., Wang, X., Zhang, Q., Yin, Q., Jian, Y., Liu, Y., Xuan, N., Li, J., Zhou, J., Liu, K., Jing, Y., Wang, X., Yang, C. Tags: Organelles, Cell Death and Autophagy, Development Articles Source Type: research
Higher-order assembly of Sorting Nexin 16 controls tubulation and distribution of neuronal endosomes
The activities of neuronal signaling receptors depend heavily on the maturation state of the endosomal compartments in which they reside. However, it remains unclear how the distribution of these compartments within the uniquely complex morphology of neurons is regulated and how this distribution itself affects signaling. Here, we identified mechanisms by which Sorting Nexin 16 (SNX16) controls neuronal endosomal maturation and distribution. We found that higher-order assembly of SNX16 via its coiled-coil (CC) domain drives membrane tubulation in vitro and endosome association in cells. In Drosophila melanogaster motor neu...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Wang, S., Zhao, Z., Rodal, A. A. Tags: Membrane and Lipid Biology, Trafficking, Neuroscience Articles Source Type: research
Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III
Lipid droplets (LDs) are neutral lipid storage organelles that transfer lipids to various organelles including peroxisomes. Here, we show that the hereditary spastic paraplegia protein M1 Spastin, a membrane-bound AAA ATPase found on LDs, coordinates fatty acid (FA) trafficking from LDs to peroxisomes through two interrelated mechanisms. First, M1 Spastin forms a tethering complex with peroxisomal ABCD1 to promote LD–peroxisome contact formation. Second, M1 Spastin recruits the membrane-shaping ESCRT-III proteins IST1 and CHMP1B to LDs via its MIT domain to facilitate LD-to-peroxisome FA trafficking, possibly through...
Source: Journal of Cell Biology - August 4, 2019 Category: Cytology Authors: Chang, C.-L., Weigel, A. V., Ioannou, M. S., Pasolli, H. A., Xu, C. S., Peale, D. R., Shtengel, G., Freeman, M., Hess, H. F., Blackstone, C., Lippincott-Schwartz, J. Tags: Disease, Organelles, Membrane and Lipid Biology, Metabolism Articles Source Type: research
