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Journal of Cell Biology

Marie Anne O'Donnell
Balla investigates how phosphoinositides control trafficking and signaling.
March 16, 2018: Journal of Cell Biology
Gi Young Lee, Deok-Gyun You, Hye-Ra Lee, Sun Wook Hwang, C Justin Lee, Young Do Yoo
Reactive oxygen species (ROS) modulator 1 (Romo1) is a nuclear-encoded mitochondrial inner membrane protein known to regulate mitochondrial ROS production and to act as an essential redox sensor in mitochondrial dynamics. Although its physiological roles have been studied for a decade, the biophysical mechanisms that explain these activities of Romo1 are unclear. In this study, we report that Romo1 is a unique mitochondrial ion channel that differs from currently identified eukaryotic ion channels. Romo1 is a highly conserved protein with structural features of class II viroporins, which are virus-encoded nonselective cation channels...
March 15, 2018: Journal of Cell Biology
Natalia Papadopoulos, Johan Lennartsson, Carl-Henrik Heldin
Translocation of full-length or fragments of receptors to the nucleus has been reported for several tyrosine kinase receptors. In this paper, we show that a fraction of full-length cell surface platelet-derived growth factor (PDGF) receptor β (PDGFRβ) accumulates in the nucleus at the chromatin and the nuclear matrix after ligand stimulation. Nuclear translocation of PDGFRβ was dependent on PDGF-BB-induced receptor dimerization, clathrin-mediated endocytosis, β-importin, and intact Golgi, occurring in both normal and cancer cells...
March 15, 2018: Journal of Cell Biology
Coralie Fassier, Amélie Fréal, Laïla Gasmi, Christian Delphin, Daniel Ten Martin, Stéphanie De Gois, Monica Tambalo, Christophe Bosc, Philippe Mailly, Céline Revenu, Leticia Peris, Susanne Bolte, Sylvie Schneider-Maunoury, Corinne Houart, Fatiha Nothias, Jean-Christophe Larcher, Annie Andrieux, Jamilé Hazan
During neural circuit assembly, extrinsic signals are integrated into changes in growth cone (GC) cytoskeleton underlying axon guidance decisions. Microtubules (MTs) were shown to play an instructive role in GC steering. However, the numerous actors required for MT remodeling during axon navigation and their precise mode of action are far from being deciphered. Using loss- and gain-of-function analyses during zebrafish development, we identify in this study the meiotic clade adenosine triphosphatase Fidgetin-like 1 (Fignl1) as a key GC-enriched MT-interacting protein in motor circuit wiring and larval locomotion...
March 13, 2018: Journal of Cell Biology
Hao Sun, Frederic Lagarrigue, Alexandre R Gingras, Zhichao Fan, Klaus Ley, Mark H Ginsberg
Integrin activation regulates adhesion, extracellular matrix assembly, and cell migration, thereby playing an indispensable role in development and in many pathological processes. A proline mutation in the central integrin β3 transmembrane domain (TMD) creates a flexible kink that uncouples the topology of the inner half of the TMD from the outer half. In this study, using leukocyte integrin α4β7, which enables development of gut-associated lymphoid tissue (GALT), we examined the biological effect of such a proline mutation and report that it impairs agonist-induced talin-mediated activation of integrin α4β7, thereby inhibiting rolling lymphocyte arrest, a key step in transmigration...
March 13, 2018: Journal of Cell Biology
Zhe Sha, Helena M Schnell, Kerstin Ruoff, Alfred Goldberg
Proteasome inhibitors are used as research tools and to treat multiple myeloma, and proteasome activity is diminished in several neurodegenerative diseases. We therefore studied how cells compensate for proteasome inhibition. In 4 h, proteasome inhibitor treatment caused dramatic and selective induction of GABARAPL1 (but not other autophagy genes) and p62 , which binds ubiquitinated proteins and GABARAPL1 on autophagosomes. Knockdown of p62 or GABARAPL1 reduced cell survival upon proteasome inhibition. p62 induction requires the transcription factor nuclear factor (erythroid-derived 2)-like 1 (Nrf1), which simultaneously induces proteasome genes...
March 13, 2018: Journal of Cell Biology
Edgar E Boczek, Simon Alberti
Small heat shock proteins (sHsps) are adenosine triphosphate-independent chaperones that protect cells from misfolded proteins. In this issue, Grousl et al. (2018. J. Cell Biol. show that the yeast sHsp Hsp42 uses a prion-like intrinsically disordered domain to bind and sequester misfolded proteins in protein deposition sites.
March 9, 2018: Journal of Cell Biology
Simon Gemble, Renata Basto
In each duplication cycle, daughter centrioles grow to the same length as their mothers. Which mechanisms regulate this fidelity to maintain centriole length is not known. In this issue, Aydogan et al. (2018. J. Cell Biol. report a novel role for Polo-like kinase 4 (Plk4). They found that Plk4 functions in a homeostatic manner to balance growth rate and growth period to set the final centriole size.
March 8, 2018: Journal of Cell Biology
Tânia Catarina Medeiros, Ryan Lee Thomas, Ruben Ghillebert, Martin Graef
Mitochondria contain tens to thousands of copies of their own genome (mitochondrial DNA [mtDNA]), creating genetic redundancy capable of buffering mutations in mitochondrial genes essential for cellular function. However, the mechanisms regulating mtDNA copy number have been elusive. Here we found that DNA synthesis and degradation by mtDNA polymerase γ (POLG) dynamically controlled mtDNA copy number in starving yeast cells dependent on metabolic homeostasis provided by autophagy. Specifically, the continuous mtDNA synthesis by POLG in starving wild-type cells was inhibited by nucleotide insufficiency and elevated mitochondria-derived reactive oxygen species in the presence of autophagy dysfunction...
March 8, 2018: Journal of Cell Biology
Corey A H Allard, Hannah E Opalko, Ko-Wei Liu, Uche Medoh, James B Moseley
Cell size control requires mechanisms that link cell growth with Cdk1 activity. In fission yeast, the protein kinase Cdr2 forms cortical nodes that include the Cdk1 inhibitor Wee1 along with the Wee1-inhibitory kinase Cdr1. We investigated how nodes inhibit Wee1 during cell growth. Biochemical fractionation revealed that Cdr2 nodes were megadalton structures enriched for activated Cdr2, which increases in level during interphase growth. In live-cell total internal reflection fluorescence microscopy videos, Cdr2 and Cdr1 remained constant at nodes over time, but Wee1 localized to nodes in short bursts...
March 7, 2018: Journal of Cell Biology
Tomoaki Sobajima, Shin-Ichiro Yoshimura, Tomomi Maeda, Haruhiko Miyata, Eiji Miyoshi, Akihiro Harada
Cholesterol, which is endocytosed to the late endosome (LE)/lysosome, is delivered to other organelles through vesicular and nonvesicular transport mechanisms. In this study, we discuss a novel mechanism of cholesterol transport from recycling endosomes (REs) to the trans-Golgi network (TGN) through RELCH/KIAA1468, which is newly identified in this study as a Rab11-GTP- and OSBP-binding protein. After treating cells with 25-hydroxycholesterol to induce OSBP relocation from the cytoplasm to the TGN, REs accumulated around the TGN area, but this accumulation was diminished in RELCH- or OSBP-depleted cells...
March 7, 2018: Journal of Cell Biology
Sun K Kim, Siwei Zhang, Michael E Werner, Eva J Brotslaw, Jennifer W Mitchell, Mohamed M Altabbaa, Brian J Mitchell
Most epithelial cells polarize along the axis of the tissue, a feature known as planar cell polarity (PCP). The initiation of PCP requires cell-cell signaling via the noncanonical Wnt/PCP pathway. Additionally, changes in the cytoskeleton both facilitate and reflect this polarity. We have identified CLAMP/Spef1 as a novel regulator of PCP signaling. In addition to decorating microtubules (MTs) and the ciliary rootlet, a pool of CLAMP localizes at the apical cell cortex. Depletion of CLAMP leads to the loss of PCP protein asymmetry, defects in cilia polarity, and defects in the angle of cell division...
March 7, 2018: Journal of Cell Biology
Chih-Hang Anthony Tang, Shiun Chang, Adrienne W Paton, James C Paton, Dmitry I Gabrilovich, Hidde L Ploegh, Juan R Del Valle, Chih-Chi Andrew Hu
To relieve endoplasmic reticulum (ER) stress, IRE1 splices XBP1 messenger RNA (mRNA) or engages regulated IRE1-dependent decay (RIDD) of other mRNAs. Upon XBP1 deficiency, IRE1 switches to perform RIDD. We examined IRE1 in XBP1-deficient B cells and discovered that IRE1 undergoes phosphorylation at S729. We generated an anti-phospho-S729 antibody to investigate such phosphorylation. Compared with pharmacological ER stress inducers or Toll-like receptor ligands, the bacterial subtilase cytotoxin has an unusual capability in causing rapid and strong phosphorylation at S729 and triggering B cells to express spliced XBP1...
March 6, 2018: Journal of Cell Biology
Sho W Suzuki, Scott D Emr
The lysosome (or vacuole in yeast) is the central organelle responsible for cellular degradation and nutrient storage. Lysosomes receive cargo from the secretory, endocytic, and autophagy pathways. Many of these proteins and lipids are delivered to the lysosome membrane, and some are degraded in the lysosome lumen, whereas others appear to be recycled through unknown pathways. In this study, we identify the transmembrane autophagy protein Atg27 as a physiological cargo recycled from the vacuole. We reveal that Atg27 is delivered to the vacuole membrane and then recycled using a two-step recycling process...
March 6, 2018: Journal of Cell Biology
Nadia Efimova, Tatyana M Svitkina
Adherens junctions (AJs) are mechanosensitive cadherin-based intercellular adhesions that interact with the actin cytoskeleton and carry most of the mechanical load at cell-cell junctions. Both Arp2/3 complex-dependent actin polymerization generating pushing force and nonmuscle myosin II (NMII)-dependent contraction producing pulling force are necessary for AJ morphogenesis. Which actin system directly interacts with AJs is unknown. Using platinum replica electron microscopy of endothelial cells, we show that vascular endothelial (VE)-cadherin colocalizes with Arp2/3 complex-positive actin networks at different AJ types and is positioned at the interface between two oppositely oriented branched networks from adjacent cells...
March 5, 2018: Journal of Cell Biology
Hebatullah Laban, Andreas Weigert, Joana Zink, Amro Elgheznawy, Christoph Schürmann, Lea Günther, Randa Abdel Malik, Sabrina Bothur, Susanne Wingert, Rolf Bremer, Michael A Rieger, Bernhard Brüne, Ralf P Brandes, Ingrid Fleming, Peter M Benz
In ischemic vascular diseases, leukocyte recruitment and polarization are crucial for revascularization and tissue repair. We investigated the role of vasodilator-stimulated phosphoprotein (VASP) in vascular repair. After hindlimb ischemia induction, blood flow recovery, angiogenesis, arteriogenesis, and leukocyte infiltration into ischemic muscles in VASP-/- mice were accelerated. VASP deficiency also elevated the polarization of the macrophages through increased signal transducer and activator of transcription (STAT) signaling, which augmented the release of chemokines, cytokines, and growth factors to promote leukocyte recruitment and vascular repair...
March 5, 2018: Journal of Cell Biology
Yuichi Tsuchiya, Michiko Saito, Hiroshi Kadokura, Jun-Ichi Miyazaki, Fumi Tashiro, Yusuke Imagawa, Takao Iwawaki, Kenji Kohno
In mammalian pancreatic β cells, the IRE1α-XBP1 pathway is constitutively and highly activated under physiological conditions. To elucidate the precise role of this pathway, we constructed β cell-specific Ire1α conditional knockout (CKO) mice and established insulinoma cell lines in which Ire1α was deleted using the Cre-loxP system. Ire1α CKO mice showed the typical diabetic phenotype including impaired glycemic control and defects in insulin biosynthesis postnatally at 4-20 weeks. Ire1α deletion in pancreatic β cells in mice and insulinoma cells resulted in decreased insulin secretion, decreased insulin and proinsulin contents in cells, and decreased oxidative folding of proinsulin along with decreased expression of five protein disulfide isomerases (PDIs): PDI, PDIR, P5, ERp44, and ERp46...
March 5, 2018: Journal of Cell Biology
Anne-Clémence Vion, Silvanus Alt, Alexandra Klaus-Bergmann, Anna Szymborska, Tuyu Zheng, Tijana Perovic, Adel Hammoutene, Marta Bastos Oliveira, Eireen Bartels-Klein, Irene Hollfinger, Pierre-Emmanuel Rautou, Miguel O Bernabeu, Holger Gerhardt
Blood flow shapes vascular networks by orchestrating endothelial cell behavior and function. How endothelial cells read and interpret flow-derived signals is poorly understood. Here, we show that endothelial cells in the developing mouse retina form and use luminal primary cilia to stabilize vessel connections selectively in parts of the remodeling vascular plexus experiencing low and intermediate shear stress. Inducible genetic deletion of the essential cilia component intraflagellar transport protein 88 (IFT88) in endothelial cells caused premature and random vessel regression without affecting proliferation, cell cycle progression, or apoptosis...
March 2, 2018: Journal of Cell Biology
Mustafa G Aydogan, Alan Wainman, Saroj Saurya, Thomas L Steinacker, Anna Caballe, Zsofia A Novak, Janina Baumbach, Nadine Muschalik, Jordan W Raff
Centrioles are highly structured organelles whose size is remarkably consistent within any given cell type. New centrioles are born when Polo-like kinase 4 (Plk4) recruits Ana2/STIL and Sas-6 to the side of an existing "mother" centriole. These two proteins then assemble into a cartwheel, which grows outwards to form the structural core of a new daughter. Here, we show that in early Drosophila melanogaster embryos, daughter centrioles grow at a linear rate during early S-phase and abruptly stop growing when they reach their correct size in mid- to late S-phase...
March 2, 2018: Journal of Cell Biology
Juliette J Lee, Alvaro Sanchez-Martinez, Aitor Martinez Zarate, Cristiane Benincá, Ugo Mayor, Michael J Clague, Alexander J Whitworth
The Parkinson's disease factors PINK1 and parkin are strongly implicated in stress-induced mitophagy in vitro, but little is known about their impact on basal mitophagy in vivo. We generated transgenic Drosophila melanogaster expressing fluorescent mitophagy reporters to evaluate the impact of Pink1/parkin mutations on basal mitophagy under physiological conditions. We find that mitophagy is readily detectable and abundant in many tissues, including Parkinson's disease-relevant dopaminergic neurons. However, we did not detect mitolysosomes in flight muscle...
March 2, 2018: Journal of Cell Biology
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