Human keratin 1/10-1B tetramer structures reveal a knob-pocket mechanism in intermediate filament assembly
To characterize keratin intermediate filament assembly mechanisms at atomic resolution, we determined the crystal structure of wild-type human keratin-1/keratin-10 helix 1B heterotetramer at 3.0 Å resolution. It revealed biochemical determinants for the A11 mode of axial alignment in keratin filaments. Four regions on a hydrophobic face of the K1/K10-1B heterodimer dictated tetramer assembly: the N-terminal hydrophobic pocket (defined by L227K1, Y230K1, F231K1, and F234K1), the K10 hydrophobic stripe, K1 interaction residues, and the C-terminal anchoring knob (formed by F314K1 and L318K1). Mutation of both knob ...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Eldirany, S. A., Ho, M., Hinbest, A. J., Lomakin, I. B., Bunick, C. G. Tags: Cell Adhesion, Polarity & Cytoskeleton, Structural Biology Articles Source Type: research
Slx5/Slx8-dependent ubiquitin hotspots on chromatin contribute to stress tolerance
Chromatin is a highly regulated environment, and protein association with chromatin is often controlled by post-translational modifications and the corresponding enzymatic machinery. Specifically, SUMO-targeted ubiquitin ligases (STUbLs) have emerged as key players in nuclear quality control, genome maintenance, and transcription. However, how STUbLs select specific substrates among myriads of SUMOylated proteins on chromatin remains unclear. Here, we reveal a remarkable co-localization of the budding yeast STUbL Slx5/Slx8 and ubiquitin at seven genomic loci that we term "ubiquitin hotspots". Ubiquitylation at these sites ...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Höpfler, M., Kern, M. J., Straub, T., Prytuliak, R., Habermann, B. H., Pfander, B., Jentsch, S. Tags: Chromatin, Epigenetics, Genomics & Functional Genomics, Post-translational Modifications, Proteolysis & Proteomics Articles Source Type: research
Triggering MSR1 promotes JNK-mediated inflammation in IL-4-activated macrophages
Alternatively activated M2 macrophages play an important role in maintenance of tissue homeostasis by scavenging dead cells, cell debris and lipoprotein aggregates via phagocytosis. Using proteomics, we investigated how alternative activation, driven by IL-4, modulated the phagosomal proteome to control macrophage function. Our data indicate that alternative activation enhances homeostatic functions such as proteolysis, lipolysis and nutrient transport. Intriguingly, we identified the enhanced recruitment of the TAK1/MKK7/JNK signalling complex to phagosomes of IL-4-activated macrophages. The recruitment of this signalling...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Guo, M., Härtlova, A., Gierlinski, M., Prescott, A., Castellvi, J., Losa, J. H., Petersen, S. K., Wenzel, U. A., Dill, B. D., Emmerich, C. H., Ramon Y Cajal, S., Russell, D. G., Trost, M. Tags: Immunology, Post-translational Modifications, Proteolysis & Proteomics, Signal Transduction Articles Source Type: research
Pten controls B-cell responsiveness and germinal center reaction by regulating the expression of IgD BCR
In contrast to other B-cell antigen receptor (BCR) classes, the function of IgD BCR on mature B cells remains largely elusive as mature B cells co-express IgM, which is sufficient for development, survival, and activation of B cells. Here, we show that IgD expression is regulated by the forkhead box transcription factor FoxO1, thereby shifting the responsiveness of mature B cells towards recognition of multivalent antigen. FoxO1 is repressed by phosphoinositide 3-kinase (PI3K) signaling and requires the lipid phosphatase Pten for its activation. Consequently, Pten-deficient B cells expressing knock-ins for BCR heavy and li...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Setz, C. S., Khadour, A., Renna, V., Iype, J., Gentner, E., He, X., Datta, M., Young, M., Nitschke, L., Wienands, J., Maity, P. C., Reth, M., Jumaa, H. Tags: Immunology, Signal Transduction Articles Source Type: research
Cancer cells induce immune escape via glycocalyx changes controlled by the telomeric protein TRF2
In this study, we describe a mechanism by which cancer cells control MDSCs in human cancers by upregulating TRF2, a protein required for telomere stability. Specifically, we showed that the TRF2 upregulation in cancer cells has extratelomeric roles in activating the expression of a network of genes involved in the biosynthesis of heparan sulfate proteoglycan, leading to profound changes in glycocalyx length and stiffness, as revealed by atomic force microscopy. This TRF2-dependent regulation facilitated the recruitment of MDSCs, their activation via the TLR2/MyD88/IL-6/STAT3 pathway leading to the inhibition of natural kil...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Cherfils-Vicini, J., Iltis, C., Cervera, L., Pisano, S., Croce, O., Sadouni, N., Gyorffy, B., Collet, R., Renault, V. M., Rey-Millet, M., Leonetti, C., Zizza, P., Allain, F., Ghiringhelli, F., Soubeiran, N., Shkreli, M., Vivier, E., Biroccio, A., Gilson, Tags: Cancer, Cell Adhesion, Polarity & Cytoskeleton, Immunology Articles Source Type: research
Local actin nucleation tunes centrosomal microtubule nucleation during passage through mitosis
Cells going through mitosis undergo precisely timed changes in cell shape and organisation, which serve to ensure the fair partitioning of cellular components into the two daughter cells. These structural changes are driven by changes in actin filament and microtubule dynamics and organisation. While most evidence suggests that the two cytoskeletal systems are remodelled in parallel during mitosis, recent work in interphase cells has implicated the centrosome in both microtubule and actin nucleation, suggesting the potential for regulatory crosstalk between the two systems. Here, by using both in vitro and in viv...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Farina, F., Ramkumar, N., Brown, L., Samandar Eweis, D., Anstatt, J., Waring, T., Bithell, J., Scita, G., Thery, M., Blanchoin, L., Zech, T., Baum, B. Tags: Cell Adhesion, Polarity & Cytoskeleton, Cell Cycle Articles Source Type: research
Actin filaments regulate microtubule growth at the centrosome
The centrosome is the main microtubule-organizing centre. It also organizes a local network of actin filaments. However, the precise function of the actin network at the centrosome is not well understood. Here, we show that increasing densities of actin filaments at the centrosome of lymphocytes are correlated with reduced amounts of microtubules. Furthermore, lymphocyte activation resulted in disassembly of centrosomal actin and an increase in microtubule number. To further investigate the direct crosstalk between actin and microtubules at the centrosome, we performed in vitro reconstitution assays based on (i) purif...
Source: EMBO Journal - June 2, 2019 Category: Molecular Biology Authors: Inoue, D., Obino, D., Pineau, J., Farina, F., Gaillard, J., Guerin, C., Blanchoin, L., Lennon-Dumenil, A.-M., Thery, M. Tags: Cell Adhesion, Polarity & Cytoskeleton, Immunology Articles Source Type: research
Chopping GSDMD: caspase-8 has joined the team of pyroptosis-mediating caspases
nflammatory and apoptotic caspases mediate two distinct forms of cell death: pyroptosis and apoptosis, respectively. Three independent studies have now demonstrated that the "apoptotic" caspase-8 can cleave gasdermin D (GSDMD) leading to pyroptosis-like cell death and IL-1β release in murine macrophages (Orning et al, 2018; Sarhan et al, 2018; Chen et al, 2019). Orning et al and Chen/Demarco et al also show that the NLRP3 inflammasome is activated downstream of active caspase-8, but they attribute this inflammasome activation to different pore-forming proteins, GSDMD and pannexin-1, respective...
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Gram, A. M., Booty, L. M., Bryant, C. E. Tags: Autophagy & Cell Death, Immunology News [amp ] Views Source Type: research
Helping daughters succeed: asymmetric distribution of glucose transporter mRNA
Rapidly proliferating cells growing by glucose fermentation must first transport glucose into the cell. Both budding yeast and human tumor cells utilize members of a conserved family of glucose transporters. In this issue of The EMBO Journal, Stahl et al (2019) reveal that budding yeast cells confer a growth advantage to their daughters using a novel mechanism, the asymmetric distribution to the daughter cell of the mRNA for a specific glucose transporter. (Source: EMBO Journal)
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: O'Donnell, A. F., Schmidt, M. C. Tags: Cell Cycle, Membrane & Intracellular Transport, Metabolism News [amp ] Views Source Type: research
Reactive oxygen species are essential for autophagy and specifically regulate the activity of Atg4
(Source: EMBO Journal)
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Scherz-Shouval, R., Shvets, E., Fass, E., Shorer, H., Gil, L., Elazar, Z. Tags: Corrigendum Source Type: research
Extrinsic and intrinsic apoptosis activate pannexin-1 to drive NLRP3 inflammasome assembly
Pyroptosis is a form of lytic inflammatory cell death driven by inflammatory caspase-1, caspase-4, caspase-5 and caspase-11. These caspases cleave and activate the pore-forming protein gasdermin D (GSDMD) to induce membrane damage. By contrast, apoptosis is driven by apoptotic caspase-8 or caspase-9 and has traditionally been classified as an immunologically silent form of cell death. Emerging evidence suggests that therapeutics designed for cancer chemotherapy or inflammatory disorders such as SMAC mimetics, TAK1 inhibitors and BH3 mimetics promote caspase-8 or caspase-9-dependent inflammatory cell death and NLRP3 inflamm...
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Chen, K. W., Demarco, B., Heilig, R., Shkarina, K., Boettcher, A., Farady, C. J., Pelczar, P., Broz, P. Tags: Autophagy & Cell Death, Immunology Articles Source Type: research
Single-cell damage elicits regional, nematode-restricting ethylene responses in roots
Plants are exposed to cellular damage by mechanical stresses, herbivore feeding, or invading microbes. Primary wound responses are communicated to neighboring and distal tissues by mobile signals. In leaves, crushing of large cell populations activates a long-distance signal, causing jasmonate production in distal organs. This is mediated by a cation channel-mediated depolarization wave and is associated with cytosolic Ca2+ transient currents. Here, we report that much more restricted, single-cell wounding in roots by laser ablation elicits non-systemic, regional surface potential changes, calcium waves, and reactive oxyge...
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Marhavy, P., Kurenda, A., Siddique, S., Denervaud Tendon, V., Zhou, F., Holbein, J., Hasan, M. S., Grundler, F. M., Farmer, E. E., Geldner, N. Tags: Plant Biology, Signal Transduction Articles Source Type: research
OTUB1 inhibits CNS autoimmunity by preventing IFN-{gamma}-induced hyperactivation of astrocytes
Astrocytes are critical regulators of neuroinflammation in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). Growing evidence indicates that ubiquitination of signaling molecules is an important cell-intrinsic mechanism governing astrocyte function during MS and EAE. Here, we identified an upregulation of the deubiquitinase OTU domain, ubiquitin aldehyde binding 1 (OTUB1) in astrocytes during MS and EAE. Mice with astrocyte-specific OTUB1 ablation developed more severe EAE due to increased leukocyte accumulation, proinflammatory gene transcription, and demyelination in the spinal...
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Wang, X., Mulas, F., Yi, W., Brunn, A., Nishanth, G., Just, S., Waisman, A., Brück, W., Deckert, M., Schlüter, D. Tags: Immunology, Neuroscience Articles Source Type: research
In situ and high-resolution cryo-EM structure of a bacterial type VI secretion system membrane complex
Bacteria have evolved macromolecular machineries that secrete effectors and toxins to survive and thrive in diverse environments. The type VI secretion system (T6SS) is a contractile machine that is related to Myoviridae phages. It is composed of a phage tail-like structure inserted in the bacterial cell envelope by a membrane complex (MC) comprising the TssJ, TssL and TssM proteins. We previously reported the low-resolution negative-stain electron microscopy structure of the enteroaggregative Escherichia coli MC and proposed a rotational 5-fold symmetry with a TssJ:TssL:TssM stoichiometry of 2:2:2. Here, cryo-electron tom...
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Rapisarda, C., Cherrak, Y., Kooger, R., Schmidt, V., Pellarin, R., Logger, L., Cascales, E., Pilhofer, M., Durand, E., Fronzes, R. Tags: Microbiology, Virology & Host Pathogen Interaction, Structural Biology Articles Source Type: research
The yeast mitochondrial pyruvate carrier is a hetero-dimer in its functional state
The mitochondrial pyruvate carrier (MPC) is critical for cellular homeostasis, as it is required in central metabolism for transporting pyruvate from the cytosol into the mitochondrial matrix. MPC has been implicated in many diseases and is being investigated as a drug target. A few years ago, small membrane proteins, called MPC1 and MPC2 in mammals and Mpc1, Mpc2 and Mpc3 in yeast, were proposed to form large protein complexes responsible for this function. However, the MPC complexes have never been isolated and their composition, oligomeric state and functional properties have not been defined. Here, we identify the func...
Source: EMBO Journal - May 14, 2019 Category: Molecular Biology Authors: Tavoulari, S., Thangaratnarajah, C., Mavridou, V., Harbour, M. E., Martinou, J.-C., Kunji, E. R. Tags: Membrane & Intracellular Transport Articles Source Type: research
