201
|
Raiborg C, Wenzel EM, Stenmark H. ER-endosome contact sites: molecular compositions and functions. EMBO J 2015; 34:1848-58. [PMID: 26041457 DOI: 10.15252/embj.201591481] [Citation(s) in RCA: 131] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 03/31/2015] [Indexed: 01/05/2023] Open
Abstract
Recent studies have revealed the existence of numerous contact sites between the endoplasmic reticulum (ER) and endosomes in mammalian cells. Such contacts increase during endosome maturation and play key roles in cholesterol transfer, endosome positioning, receptor dephosphorylation, and endosome fission. At least 7 distinct contact sites between the ER and endosomes have been identified to date, which have diverse molecular compositions. Common to these contact sites is that they impose a close apposition between the ER and endosome membranes, which excludes membrane fusion while allowing the flow of molecular signals between the two membranes, in the form of enzymatic modifications, or ion, lipid, or protein transfer. Thus, ER-endosome contact sites ensure coordination of molecular activities between the two compartments while keeping their general compositions intact. Here, we review the molecular architectures and cellular functions of known ER-endosome contact sites and discuss their implications for human health.
Collapse
Affiliation(s)
- Camilla Raiborg
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway Department of Molecular Cell Biology, Institute for Cancer Research Oslo University Hospital, Oslo, Norway
| | - Eva M Wenzel
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway Department of Molecular Cell Biology, Institute for Cancer Research Oslo University Hospital, Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway Department of Molecular Cell Biology, Institute for Cancer Research Oslo University Hospital, Oslo, Norway Centre of Molecular Inflammation Research, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| |
Collapse
|
202
|
Zehner M, Marschall A, Bos E, Schloetel JG, Kreer C, Fehrenschild D, Limmer A, Ossendorp F, Lang T, Koster A, Dübel S, Burgdorf S. The Translocon Protein Sec61 Mediates Antigen Transport from Endosomes in the Cytosol for Cross-Presentation to CD8+ T Cells. Immunity 2015; 42:850-63. [DOI: 10.1016/j.immuni.2015.04.008] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 02/18/2015] [Accepted: 04/22/2015] [Indexed: 12/20/2022]
|
203
|
Tan X, Thapa N, Sun Y, Anderson RA. A kinase-independent role for EGF receptor in autophagy initiation. Cell 2015; 160:145-60. [PMID: 25594178 DOI: 10.1016/j.cell.2014.12.006] [Citation(s) in RCA: 179] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/21/2014] [Accepted: 11/19/2014] [Indexed: 12/30/2022]
Abstract
The epidermal growth factor receptor (EGFR) is upregulated in numerous human cancers. Inhibition of EGFR signaling induces autophagy in tumor cells. Here, we report an unanticipated role for the inactive EGFR in autophagy initiation. Inactive EGFR interacts with the oncoprotein LAPTM4B that is required for the endosomal accumulation of EGFR upon serum starvation. Inactive EGFR and LAPTM4B stabilize each other at endosomes and recruit the exocyst subcomplex containing Sec5. We show that inactive EGFR, LAPTM4B, and the Sec5 subcomplex are required for basal and starvation-induced autophagy. LAPTM4B and Sec5 promote EGFR association with the autophagy inhibitor Rubicon, which in turn disassociates Beclin 1 from Rubicon to initiate autophagy. Thus, the oncoprotein LAPTM4B facilitates the role of inactive EGFR in autophagy initiation. This pathway is positioned to control tumor metabolism and promote tumor cell survival upon serum deprivation or metabolic stress.
Collapse
Affiliation(s)
- Xiaojun Tan
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Narendra Thapa
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Yue Sun
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Richard A Anderson
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA.
| |
Collapse
|
204
|
Repeated ER–endosome contacts promote endosome translocation and neurite outgrowth. Nature 2015; 520:234-8. [DOI: 10.1038/nature14359] [Citation(s) in RCA: 283] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2014] [Accepted: 02/27/2015] [Indexed: 01/03/2023]
|
205
|
van der Goot FG, Gruenberg J. Close encounter of the third kind: the ER meets endosomes at fission sites. Dev Cell 2015; 31:673-4. [PMID: 25535914 DOI: 10.1016/j.devcel.2014.12.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The endoplasmic reticulum (ER) forms functional contacts with several cellular organelles and regulates processes such as mitochondrial fission. In a recent issue of Cell, Rowland et al. (2014) extend these findings to endosomes, showing that the ER contacts endosomes at sites containing the WASH subunit FAM21, where it forecasts fission events.
Collapse
Affiliation(s)
- F Gisou van der Goot
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 19, CH-1015 Lausanne, Switzerland.
| | - Jean Gruenberg
- Department of Biochemistry, University of Geneva, 30 quai E. Ansermet, 1211-Geneva-4, Switzerland.
| |
Collapse
|
206
|
Rowland AA, Chitwood PJ, Phillips MJ, Voeltz GK. ER contact sites define the position and timing of endosome fission. Cell 2015; 159:1027-1041. [PMID: 25416943 DOI: 10.1016/j.cell.2014.10.023] [Citation(s) in RCA: 296] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 08/13/2014] [Accepted: 09/24/2014] [Indexed: 10/24/2022]
Abstract
Endocytic cargo and Rab GTPases are segregated to distinct domains of an endosome. These domains maintain their identity until they undergo fission to traffic cargo. It is not fully understood how segregation of cargo or Rab proteins is maintained along the continuous endosomal membrane or what machinery is required for fission. Endosomes form contact sites with the endoplasmic reticulum (ER) that are maintained during trafficking. Here, we show that stable contacts form between the ER and endosome at constricted sorting domains, and free diffusion of cargo is limited at these positions. We demonstrate that the site of constriction and fission for early and late endosomes is spatially and temporally linked to contact sites with the ER. Lastly, we show that altering ER structure and dynamics reduces the efficiency of endosome fission. Together, these data reveal a surprising role for ER contact in defining the timing and position of endosome fission.
Collapse
Affiliation(s)
- Ashley A Rowland
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Patrick J Chitwood
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Melissa J Phillips
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Gia K Voeltz
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
| |
Collapse
|
207
|
Penny CJ, Kilpatrick BS, Eden ER, Patel S. Coupling acidic organelles with the ER through Ca²⁺ microdomains at membrane contact sites. Cell Calcium 2015; 58:387-96. [PMID: 25866010 DOI: 10.1016/j.ceca.2015.03.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 03/13/2015] [Accepted: 03/14/2015] [Indexed: 10/23/2022]
Abstract
Acidic organelles such as lysosomes serve as non-canonical Ca(2+) stores. The Ca(2+) mobilising messenger NAADP is thought to trigger local Ca(2+) release from such stores. These events are then amplified by Ca(2+) channels on canonical ER Ca(2+) stores to generate physiologically relevant global Ca(2+) signals. Coupling likely occurs at microdomains formed at membrane contact sites between acidic organelles and the ER. Molecular analyses and computational modelling suggest heterogeneity in the composition of these contacts and predicted Ca(2+) microdomain behaviour. Conversely, acidic organelles might also locally amplify and temper ER-evoked Ca(2+) signals. Ca(2+) microdomains between distinct Ca(2+) stores are thus likely to be integral to the genesis of complex Ca(2+) signals.
Collapse
Affiliation(s)
- Christopher J Penny
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Bethan S Kilpatrick
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Emily R Eden
- Department of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
| |
Collapse
|
208
|
Fluorescence methods for analysis of interactions between Ca(2+) signaling, lysosomes, and endoplasmic reticulum. Methods Cell Biol 2015. [PMID: 25665449 DOI: 10.1016/bs.mcb.2014.10.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The endoplasmic reticulum (ER) is both the major source of intracellular Ca(2+) for cell signaling and the organelle that forms the most extensive contacts with the plasma membrane and other organelles. Lysosomes fulfill important roles in degrading cellular materials and in cholesterol handling, but they also contribute to Ca(2+) signaling by both releasing and sequestering Ca(2+). Interactions between ER and other Ca(2+)-transporting membranes, notably mitochondria and the plasma membrane, often occur at sites where the two membranes are closely apposed, allowing local Ca(2+) signaling between them. These interactions are often facilitated by scaffold proteins. Recent evidence suggests similar local interactions between ER and lysosomes. We describe simple fluorescence-based methods that allow the interplay between Ca(2+) signals, the ER, and lysosomes to be examined.
Collapse
|
209
|
Burgoyne T, Patel S, Eden ER. Calcium signaling at ER membrane contact sites. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2012-7. [PMID: 25662816 DOI: 10.1016/j.bbamcr.2015.01.022] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 01/26/2015] [Accepted: 01/28/2015] [Indexed: 11/27/2022]
Abstract
Communication between organelles is a necessary consequence of intracellular compartmentalization. Membrane contact sites (MCSs) are regions where the membranes of two organelles come into close apposition allowing exchange of small molecules and ions including Ca²⁺. The ER, the cell's major Ca²⁺ store, forms an extensive and dynamic network of contacts with multiple organelles. Here we review established and emerging roles of ER contacts as platforms for Ca²⁺ exchange and further consider a potential role for Ca²⁺ in the regulation of MCS formation. We additionally discuss the challenges associated with the study of MCS biology and highlight advances in microscopy-based solutions. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.
Collapse
Affiliation(s)
| | - Sandip Patel
- Department of Cell and Developmental Biology, UCL, London, UK
| | | |
Collapse
|
210
|
Westrate LM, Lee JE, Prinz WA, Voeltz GK. Form follows function: the importance of endoplasmic reticulum shape. Annu Rev Biochem 2015; 84:791-811. [PMID: 25580528 DOI: 10.1146/annurev-biochem-072711-163501] [Citation(s) in RCA: 266] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The endoplasmic reticulum (ER) has a remarkably complex structure, composed of a single bilayer that forms the nuclear envelope, along with a network of sheets and dynamic tubules. Our understanding of the biological significance of the complex architecture of the ER has improved dramatically in the last few years. The identification of proteins and forces required for maintaining ER shape, as well as more advanced imaging techniques, has allowed the relationship between ER shape and function to come into focus. These studies have also revealed unexpected new functions of the ER and novel ER domains regulating alterations in ER dynamics. The importance of ER structure has become evident as recent research has identified diseases linked to mutations in ER-shaping proteins. In this review, we discuss what is known about the maintenance of ER architecture, the relationship between ER structure and function, and diseases associated with defects in ER structure.
Collapse
Affiliation(s)
- L M Westrate
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80303;
| | | | | | | |
Collapse
|
211
|
Membrane contact sites, gateways for lipid homeostasis. Curr Opin Cell Biol 2015; 33:82-87. [PMID: 25569848 DOI: 10.1016/j.ceb.2014.12.004] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 12/08/2014] [Accepted: 12/15/2014] [Indexed: 12/21/2022]
Abstract
Maintaining the proper lipid composition of cellular membranes is critical for numerous cellular processes but mechanisms of membrane lipid homeostasis are not well understood. There is growing evidence that membrane contact sites (MCSs), regions where two organelles come in close proximity to one another, play major roles in the regulation of intracellular lipid composition and distribution. MCSs are thought to mediate the exchange of lipids and signals between organelles. In this review, we discuss how lipid exchange occurs at MCSs and evidence for roles of MCSs in regulating lipid synthesis and degradation. We also discuss how networks of organelles connected by MCSs may modulate cellular lipid homeostasis and help determine organelle lipid composition.
Collapse
|
212
|
Sorting nexin 6 enhances lamin a synthesis and incorporation into the nuclear envelope. PLoS One 2014; 9:e115571. [PMID: 25535984 PMCID: PMC4275242 DOI: 10.1371/journal.pone.0115571] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 10/21/2014] [Indexed: 01/20/2023] Open
Abstract
Nuclear lamins are important structural and functional proteins in mammalian cells, but little is known about the mechanisms and cofactors that regulate their traffic into the nucleus. Here, we demonstrate that trafficking of lamin A, but not lamin B1, and its assembly into the nuclear envelope are regulated by sorting nexin 6 (SNX6), a major component of the retromer that targets proteins and other molecules to specific subcellular locations. SNX6 interacts with lamin A in vitro and in vivo and links it to the outer surface of the endoplasmic reticulum in human and mouse cells. SNX6 transports its lamin A cargo to the nuclear envelope in a process that takes several hours. Lamin A protein levels in the nucleus augment or decrease, respectively, upon gain or loss of SNX6 function. We further show that SNX6-dependent lamin A nuclear import occurs across the nuclear pore complex via a RAN-GTP-dependent mechanism. These results identify SNX6 as a key regulator of lamin A synthesis and incorporation into the nuclear envelope.
Collapse
|
213
|
Abstract
Endosomes are known to undergo budding and fission reactions that separate regions destined for lysosomal degradation from carriers to be recycled to the plasma membrane. A recent paper (Rowland et al, 2014) shows that contact sites between endosomes and the endoplasmic reticulum (ER) define the position and timing for fission. This uncovers an unanticipated role for the ER in controlling endosomal sorting and maturation.
Collapse
Affiliation(s)
- Camilla Raiborg
- Centre for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, Montebello Oslo, Norway Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, Montebello Oslo, Norway Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello Oslo, Norway
| |
Collapse
|
214
|
Jongsma MLM, Berlin I, Neefjes J. On the move: organelle dynamics during mitosis. Trends Cell Biol 2014; 25:112-24. [PMID: 25466831 DOI: 10.1016/j.tcb.2014.10.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 10/23/2014] [Accepted: 10/28/2014] [Indexed: 10/24/2022]
Abstract
A cell constitutes the minimal self-replicating unit of all organisms, programmed to propagate its genome as it proceeds through mitotic cell division. The molecular processes entrusted with ensuring high fidelity of DNA replication and subsequent segregation of chromosomes between daughter cells have therefore been studied extensively. However, to process the information encoded in its genome a cell must also pass on its non-genomic identity to future generations. To achieve productive sharing of intracellular organelles, cells have evolved complex mechanisms of organelle inheritance. Many membranous compartments undergo vast spatiotemporal rearrangements throughout mitosis. These controlled organizational changes are crucial to enabling completion of the division cycle and ensuring successful progeny. Herein we review current understanding of intracellular organelle segregation during mitotic division in mammalian cells, with a focus on compartment organization and integrity throughout the inheritance process.
Collapse
Affiliation(s)
- Marlieke L M Jongsma
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Ilana Berlin
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Jacques Neefjes
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
| |
Collapse
|
215
|
Wandinger-Ness A, Zerial M. Rab proteins and the compartmentalization of the endosomal system. Cold Spring Harb Perspect Biol 2014; 6:a022616. [PMID: 25341920 PMCID: PMC4413231 DOI: 10.1101/cshperspect.a022616;] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Of the approximately 70 human Rab GTPases, nearly three-quarters are involved in endocytic trafficking. Significant plasticity in endosomal membrane transport pathways is closely coupled to receptor signaling and Rab GTPase-regulated scaffolds. Here we review current literature pertaining to endocytic Rab GTPase localizations, functions, and coordination with regulatory proteins and effectors. The roles of Rab GTPases in (1) compartmentalization of the endocytic pathway into early, recycling, late, and lysosomal routes; (2) coordination of individual transport steps from vesicle budding to fusion; (3) effector interactomes; and (4) integration of GTPase and signaling cascades are discussed.
Collapse
Affiliation(s)
- Angela Wandinger-Ness
- Department of Pathology MSC08 4640, University of New Mexico HSC, Albuquerque, New Mexico 87131
| | - Marino Zerial
- Max Planck Institute of Molecular and Cell Biology and Genetics, 01307 Dresden, Germany
| |
Collapse
|
216
|
Wandinger-Ness A, Zerial M. Rab proteins and the compartmentalization of the endosomal system. Cold Spring Harb Perspect Biol 2014; 6:a022616. [PMID: 25341920 DOI: 10.1101/cshperspect.a022616] [Citation(s) in RCA: 414] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Of the approximately 70 human Rab GTPases, nearly three-quarters are involved in endocytic trafficking. Significant plasticity in endosomal membrane transport pathways is closely coupled to receptor signaling and Rab GTPase-regulated scaffolds. Here we review current literature pertaining to endocytic Rab GTPase localizations, functions, and coordination with regulatory proteins and effectors. The roles of Rab GTPases in (1) compartmentalization of the endocytic pathway into early, recycling, late, and lysosomal routes; (2) coordination of individual transport steps from vesicle budding to fusion; (3) effector interactomes; and (4) integration of GTPase and signaling cascades are discussed.
Collapse
Affiliation(s)
- Angela Wandinger-Ness
- Department of Pathology MSC08 4640, University of New Mexico HSC, Albuquerque, New Mexico 87131
| | - Marino Zerial
- Max Planck Institute of Molecular and Cell Biology and Genetics, 01307 Dresden, Germany
| |
Collapse
|
217
|
Grimm C, Holdt LM, Chen CC, Hassan S, Müller C, Jörs S, Cuny H, Kissing S, Schröder B, Butz E, Northoff B, Castonguay J, Luber CA, Moser M, Spahn S, Lüllmann-Rauch R, Fendel C, Klugbauer N, Griesbeck O, Haas A, Mann M, Bracher F, Teupser D, Saftig P, Biel M, Wahl-Schott C. High susceptibility to fatty liver disease in two-pore channel 2-deficient mice. Nat Commun 2014; 5:4699. [DOI: 10.1038/ncomms5699] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 07/10/2014] [Indexed: 12/15/2022] Open
|
218
|
Daniele T, Schiaffino MV. Organelle biogenesis and interorganellar connections: Better in contact than in isolation. Commun Integr Biol 2014; 7:e29587. [PMID: 25346798 PMCID: PMC4203768 DOI: 10.4161/cib.29587] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 06/15/2014] [Indexed: 12/22/2022] Open
Abstract
Membrane contact sites (MCSs) allow the exchange of molecules and information between organelles, even when their membranes cannot fuse directly. In recent years, a number of functions have been attributed to these contacts, highlighting their critical role in cell homeostasis. Although inter-organellar connections typically involve the endoplasmic reticulum (ER), we recently reported the presence of a novel MCSs between melanosomes and mitochondria. Melanosome-mitochondrion contacts appear mediated by fibrillar bridges resembling the protein tethers linking mitochondria and the ER, both for their ultrastructural features and the involvement of Mitofusin 2. The frequency of these connections correlates spatially and timely with melanosome biogenesis, suggesting a functional link between the 2 processes and in general that organelle biogenesis in the secretory pathway requires interorganellar crosstalks at multiple steps. Here, we summarize the different functions attributed to MCSs, and discuss their possible relevance for the newly identified melanosome-mitochondrion liaison.
Collapse
Affiliation(s)
- Tiziana Daniele
- San Raffaele Scientific Institute; Experimental Imaging Center; Milan, Italy ; University of Genoa; Department of Experimental Medicine; Genoa, Italy
| | | |
Collapse
|
219
|
Fu MM, Holzbaur ELF. Integrated regulation of motor-driven organelle transport by scaffolding proteins. Trends Cell Biol 2014; 24:564-74. [PMID: 24953741 DOI: 10.1016/j.tcb.2014.05.002] [Citation(s) in RCA: 205] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 05/06/2014] [Accepted: 05/08/2014] [Indexed: 12/25/2022]
Abstract
Intracellular trafficking pathways, including endocytosis, autophagy, and secretion, rely on directed organelle transport driven by the opposing microtubule motor proteins kinesin and dynein. Precise spatial and temporal targeting of vesicles and organelles requires the integrated regulation of these opposing motors, which are often bound simultaneously to the same cargo. Recent progress demonstrates that organelle-associated scaffolding proteins, including Milton/TRAKs (trafficking kinesin-binding protein), JIP1, JIP3 (JNK-interacting proteins), huntingtin, and Hook1, interact with molecular motors to coordinate activity and sustain unidirectional transport. Scaffolding proteins also bind to upstream regulatory proteins, including kinases and GTPases, to modulate transport in the cell. This integration of regulatory control with motor activity allows for cargo-specific changes in the transport or targeting of organelles in response to cues from the complex cellular environment.
Collapse
Affiliation(s)
- Meng-meng Fu
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
| |
Collapse
|
220
|
Abstract
Live-cell imaging reveals the endolysosomal system as a complex and highly dynamic network of interacting compartments. Distinct types of endosomes are discerned by kinetic, molecular, and morphological criteria. Although none of these criteria, or combinations thereof, can capture the full complexity of the endolysosomal system, they are extremely useful for experimental purposes. Some membrane domain specializations and specific morphological characteristics can only be seen by ultrastructural analysis after preparation for electron microscopy (EM). Immuno-EM allows a further discrimination of seemingly identical compartments by their molecular makeup. In this review we provide an overview of the ultrastructural characteristics and membrane organization of endosomal compartments, along with their organizing machineries.
Collapse
Affiliation(s)
- Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Graça Raposo
- Institut Curie, Centre de Recherche, Paris F-75248, France Structure and Membrane Compartments CNRS UMR144, Paris F-75248, France
| |
Collapse
|
221
|
Lobingier BT, Nickerson DP, Lo SY, Merz AJ. SM proteins Sly1 and Vps33 co-assemble with Sec17 and SNARE complexes to oppose SNARE disassembly by Sec18. eLife 2014; 3:e02272. [PMID: 24837546 PMCID: PMC4060006 DOI: 10.7554/elife.02272] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Secretory and endolysosomal fusion events are driven by SNAREs and cofactors, including Sec17/α-SNAP, Sec18/NSF, and Sec1/Munc18 (SM) proteins. SMs are essential for fusion in vivo, but the basis of this requirement is enigmatic. We now report that, in addition to their established roles as fusion accelerators, SM proteins Sly1 and Vps33 directly shield SNARE complexes from Sec17- and Sec18-mediated disassembly. In vivo, wild-type Sly1 and Vps33 function are required to withstand overproduction of Sec17. In vitro, Sly1 and Vps33 impede SNARE complex disassembly by Sec18 and ATP. Unexpectedly, Sec17 directly promotes selective loading of Sly1 and Vps33 onto cognate SNARE complexes. A large thermodynamic barrier limits SM binding, implying that significant conformational rearrangements are involved. In a working model, Sec17 and SMs accelerate fusion mediated by cognate SNARE complexes and protect them from NSF-mediated disassembly, while mis-assembled or non-cognate SNARE complexes are eliminated through kinetic proofreading by Sec18. DOI:http://dx.doi.org/10.7554/eLife.02272.001 Eukaryotic organisms, from single-celled yeast to humans, divide their cells into membrane-bound compartments (organelles) of distinct function. To move from one compartment to another, or to enter or exit a cell, large molecules like proteins are packaged into small membrane sacs called vesicles. To release its cargo, the membrane of a vesicle must fuse with the membrane of the correct destination compartment. The SNARE family of proteins plays a key role in this fusion process. As the membranes of a vesicle and target compartment come close, SNARE proteins located on each membrane form a SNARE complex that tethers the vesicle in place and causes the two membranes fuse. SNARE proteins do not act alone in this process: the SM family of proteins also plays an essential role in SNARE-mediated membrane fusion. However, it is still not clear exactly why the SM proteins are needed. Lobingier et al. used the yeast model organism and biochemical studies with purified proteins to show that SM proteins help SNARE complexes form at the right time by regulating the delicate balance between SNARE complex formation and disassembly. This is achieved through the interplay of SM proteins and two other proteins (Sec17 and Sec18). Sec17 is known to load Sec18 onto SNARE complexes to break them apart. Lobingier et al. showed that Sec17 can also load SM proteins on SNARE complexes. This hinders Sec18 action, and so helps to keep the SNARE complexes intact. Because each SM protein tested only binds to the SNARE complex that should function at the membrane where the SM protein resides, these findings suggest SM proteins perform quality control at potential sites of membrane fusion. DOI:http://dx.doi.org/10.7554/eLife.02272.002
Collapse
Affiliation(s)
- Braden T Lobingier
- Department of Biochemistry, University of Washington School of Medicine, Seattle, United States
| | - Daniel P Nickerson
- Department of Biochemistry, University of Washington School of Medicine, Seattle, United States
| | - Sheng-Ying Lo
- Department of Biochemistry, University of Washington School of Medicine, Seattle, United States
| | - Alexey J Merz
- Department of Biochemistry, University of Washington School of Medicine, Seattle, United States Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, United States
| |
Collapse
|
222
|
Wu J, Bakerink KJ, Evangelista ME, Thomas GH. Cytoplasmic capes are nuclear envelope intrusions that are enriched in endosomal proteins and depend upon βH-spectrin and Annexin B9. PLoS One 2014; 9:e93680. [PMID: 24705398 PMCID: PMC3976414 DOI: 10.1371/journal.pone.0093680] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 03/07/2014] [Indexed: 11/18/2022] Open
Abstract
It is increasingly recognized that non-erythroid spectrins have roles remote from the plasma membrane, notably in endomembrane trafficking. The large spectrin isoform, βH, partners with Annexin B9 to modulate endosomal processing of internalized proteins. This modulation is focused on the early endosome through multivesicular body steps of endocytic processing and loss of either protein appears to cause a traffic jam before removal of ubiquitin at the multivesicular body. We previously reported that βH/Annexin B9 influenced EGF receptor signaling. While investigating this effect we noticed that mSptiz, the membrane bound precursor of the secreted EGF receptor ligand sSpitz, is located in striking intrusions of the nuclear membrane. Here we characterize these structures and identify them as ‘cytoplasmic capes’, which were previously identified in old ultrastructural studies and probably coincide with recently recognized sites of non-nuclear-pore RNA export. We show that cytoplasmic capes contain multiple endosomal markers and that their existence is dependent upon βH and Annexin B9. Diminution of these structures does not lead to a change in mSpitz processing. These results extend the endosomal influence of βH and its partner Annexin B9 to this unusual compartment at the nuclear envelope.
Collapse
Affiliation(s)
- Juan Wu
- Departments of Biology and of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- School of Public Health, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Katelyn J. Bakerink
- Departments of Biology and of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Meagan E. Evangelista
- Departments of Biology and of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Graham H. Thomas
- Departments of Biology and of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
| |
Collapse
|
223
|
Joensuu M, Belevich I, Rämö O, Nevzorov I, Vihinen H, Puhka M, Witkos TM, Lowe M, Vartiainen MK, Jokitalo E. ER sheet persistence is coupled to myosin 1c-regulated dynamic actin filament arrays. Mol Biol Cell 2014; 25:1111-26. [PMID: 24523293 PMCID: PMC3967974 DOI: 10.1091/mbc.e13-12-0712] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/17/2014] [Accepted: 01/28/2014] [Indexed: 11/11/2022] Open
Abstract
The endoplasmic reticulum (ER) comprises a dynamic three-dimensional (3D) network with diverse structural and functional domains. Proper ER operation requires an intricate balance within and between dynamics, morphology, and functions, but how these processes are coupled in cells has been unclear. Using live-cell imaging and 3D electron microscopy, we identify a specific subset of actin filaments localizing to polygons defined by ER sheets and tubules and describe a role for these actin arrays in ER sheet persistence and, thereby, in maintenance of the characteristic network architecture by showing that actin depolymerization leads to increased sheet fluctuation and transformations and results in small and less abundant sheet remnants and a defective ER network distribution. Furthermore, we identify myosin 1c localizing to the ER-associated actin filament arrays and reveal a novel role for myosin 1c in regulating these actin structures, as myosin 1c manipulations lead to loss of the actin filaments and to similar ER phenotype as observed after actin depolymerization. We propose that ER-associated actin filaments have a role in ER sheet persistence regulation and thus support the maintenance of sheets as a stationary subdomain of the dynamic ER network.
Collapse
Affiliation(s)
- Merja Joensuu
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Ilya Belevich
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
- Electron Microscopy Unit, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Olli Rämö
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Ilya Nevzorov
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
- Electron Microscopy Unit, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Maija Puhka
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Tomasz M. Witkos
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Martin Lowe
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Maria K. Vartiainen
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
- Electron Microscopy Unit, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| |
Collapse
|
224
|
van der Kant R, Neefjes J. Small regulators, major consequences - Ca²⁺ and cholesterol at the endosome-ER interface. J Cell Sci 2014; 127:929-38. [PMID: 24554437 DOI: 10.1242/jcs.137539] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The ER is the largest cellular compartment and a major storage site for lipids and ions. In recent years, much attention has focused on contacts between the ER and other organelles, and one particularly intimate relationship is that between the ER and the endosomal system. ER-endosome contacts intensify when endosomes mature, and the ER participates in endosomal processes, such as the termination of surface receptor signaling, multi-vesicular body formation, and transport and fusion events. Cholesterol and Ca(2+) are transferred between the ER and endosomes, possibly acting as messengers for ER-endosome crosstalk. Here, we summarize different types of ER-endosomal communication and discuss membrane contact sites that might facilitate this crosstalk. We review the protein pairs that interact at the ER-endosome interface and find that many of these have a role in cholesterol exchange. We also summarize Ca(2+) exchange between the ER and endosomes, and hypothesize that ER-endosome contacts integrate several cellular functions to guide endosomal maturation. We post the hypothesis that failure in ER-endosome contacts is an unrecognized but important contributor to diseases, such as Niemann-Pick type C disease, Alzheimer's disease and amyotrophic lateral sclerosis.
Collapse
Affiliation(s)
- Rik van der Kant
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | | |
Collapse
|
225
|
Sensory neuropathy with bone destruction due to a mutation in the membrane-shaping atlastin GTPase 3. Brain 2014; 137:683-92. [DOI: 10.1093/brain/awt357] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
|
226
|
Hönscher C, Ungermann C. A close-up view of membrane contact sites between the endoplasmic reticulum and the endolysosomal system: from yeast to man. Crit Rev Biochem Mol Biol 2014; 49:262-8. [PMID: 24382115 DOI: 10.3109/10409238.2013.875512] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Maintenance of organelle identity is crucial for the functionality of eukaryotic cells. Hence, transfer reactions between different compartments must be highly efficient and tightly regulated at the same time. Membrane contact sites (MCSs) represent an important route for inter-organelle transport and communication independent of vesicular trafficking. Due to extensive research, the mechanistic understanding of these sites increases constantly. However, how the formation and the versatile functions of MCSs are regulated is mainly unclear. Within this review, we focus on one well-known MCS, the nucleus-vacuole junction in yeast and discuss its analogy to endoplasmic reticulum-late endosome contacts in metazoan. Formation of the junction in yeast requires Vac8, a protein that is involved in various cellular processes at the yeast vacuole and a target of multiple posttranslational modifications. We discuss the possibility that dual functionality of proteins involved in contact formation is a common principle to coordinate inter-organelle transfer with organellar biogenesis.
Collapse
Affiliation(s)
- Carina Hönscher
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück , Osnabrück , Germany
| | | |
Collapse
|
227
|
Profiling of the mammalian mitotic spindle proteome reveals an ER protein, OSTD-1, as being necessary for cell division and ER morphology. PLoS One 2013; 8:e77051. [PMID: 24130834 PMCID: PMC3794981 DOI: 10.1371/journal.pone.0077051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 08/28/2013] [Indexed: 11/19/2022] Open
Abstract
Cell division is important for many cellular processes including cell growth, reproduction, wound healing and stem cell renewal. Failures in cell division can often lead to tumors and birth defects. To identify factors necessary for this process, we implemented a comparative profiling strategy of the published mitotic spindle proteome from our laboratory. Of the candidate mammalian proteins, we determined that 77% had orthologs in Caenorhabditis elegans and 18% were associated with human disease. Of the C. elegans candidates (n=146), we determined that 34 genes functioned in embryonic development and 56% of these were predicted to be membrane trafficking proteins. A secondary, visual screen to detect distinct defects in cell division revealed 21 genes that were necessary for cytokinesis. One of these candidates, OSTD-1, an ER resident protein, was further characterized due to the aberrant cleavage furrow placement and failures in division. We determined that OSTD-1 plays a role in maintaining the dynamic morphology of the ER during the cell cycle. In addition, 65% of all ostd-1 RNAi-treated embryos failed to correctly position cleavage furrows, suggesting that proper ER morphology plays a necessary function during animal cell division.
Collapse
|
228
|
Alpy F, Rousseau A, Schwab Y, Legueux F, Stoll I, Wendling C, Spiegelhalter C, Kessler P, Mathelin C, Rio MC, Levine TP, Tomasetto C. STARD3 or STARD3NL and VAP form a novel molecular tether between late endosomes and the ER. J Cell Sci 2013; 126:5500-12. [PMID: 24105263 DOI: 10.1242/jcs.139295] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inter-organelle membrane contacts sites (MCSs) are specific subcellular regions favoring the exchange of metabolites and information. We investigated the potential role of the late-endosomal membrane-anchored proteins StAR related lipid transfer domain-3 (STARD3) and STARD3 N-terminal like (STARD3NL) in the formation of MCSs involving late-endosomes (LEs). We demonstrate that both STARD3 and STARD3NL create MCSs between LEs and the endoplasmic reticulum (ER). STARD3 and STARD3NL use a conserved two phenylalanines in an acidic tract (FFAT)-motif to interact with ER-anchored VAP proteins. Together, they form an LE-ER tethering complex allowing heterologous membrane apposition. This LE-ER tethering complex affects organelle dynamics by altering the formation of endosomal tubules. An in situ proximity ligation assay between STARD3, STARD3NL and VAP proteins identified endogenous LE-ER MCS. Thus, we report here the identification of proteins involved in inter-organellar interaction.
Collapse
Affiliation(s)
- Fabien Alpy
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Functional Genomics and Cancer Department, 1 rue Laurent Fries, Illkirch, 67404, France
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|