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Rab Endosomes

Marita Borg Distefano, Linda Hofstad Haugen, Yan Wang, Harmonie Perdreau-Dahl, Ingrid Kjos, Da Jia, Jens Preben Morth, Jacques Neefjes, Oddmund Bakke, Cinzia Progida
Rab GTPases are key regulators of intracellular trafficking, and cycle between a GTP-bound active state and a GDP-bound inactive state. This cycle is regulated by guanine-nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). Several efforts have been made in connecting the correct GEFs and GAPs to their specific Rab. Here we aimed to identify GAPs for Rab7b, the small GTPase involved in transport from late endosomes to the trans-Golgi. An siRNA screen targeting proteins containing TBC domains critical for Rab GAPs was performed and coupled to a phenotypic read-out that visualized the distribution of Rab7b...
August 15, 2018: Journal of Cell Science
Carla Brillada, Jiameng Zheng, Falco Krüger, Eliezer Rovira-Diaz, Jana Christin Askani, Karin Schumacher, Marcela Rojas-Pierce
The vacuole is an essential organelle in plant cells, and its dynamic nature is important for plant growth and development. Homotypic membrane fusion is required for vacuole biogenesis, pollen germination, stomata opening, and gravity perception. Known components of the vacuole fusion machinery in eukaryotes include SNARE proteins, Rab GTPases, phosphoinositides, and the homotypic fusion and vacuolar protein sorting (HOPS) tethering complex. HOPS function is not well characterized in plants, but roles in embryogenesis and pollen tube elongation have been reported...
August 13, 2018: Proceedings of the National Academy of Sciences of the United States of America
Noga Budick-Harmelin, Marta Miaczynska
Maintenance of physiologic cellular functions and homeostasis requires highly coordinated interactions between different cellular compartments. In this regard, the endocytic system, which plays a key role in cargo internalization and trafficking within the cell, participates in upkeep of intracellular dynamics, while communicating with multiple organelles. This chapter will discuss the function of endosomes from a standpoint of cellular integration. We will present examples of different types of interactions between endosomes and other cellular compartments, such as the endoplasmic reticulum (ER), mitochondria, the plasma membrane (PM), and the nuclear envelope...
2018: Progress in Molecular and Subcellular Biology
Maria Podinovskaia, Anne Spang
Endocytosis is a means for the cell to sample its environment for nutrients and regulate plasma membrane (PM) composition and area. Whereas the majority of internalized cargo is recycled back to the cell surface, select material is sent to the lysosome for degradation. Endosomes further play major roles in central cell activities as diverse as establishment of cell polarity and signaling, lysosomal storage and immunity. The complexity of endosomal functions is reflected by the extensive changes to endosome properties as they mature...
2018: Progress in Molecular and Subcellular Biology
Chiara Vantaggiato, Elena Panzeri, Marianna Castelli, Andrea Citterio, Alessia Arnoldi, Filippo Maria Santorelli, Rocco Liguori, Marina Scarlato, Olimpia Musumeci, Antonio Toscano, Emilio Clementi, Maria Teresa Bassi
ZFYVE26/Spastizin and SPG11/Spatacsin encode 2 large proteins that are mutated in hereditary autosomal-recessive spastic paraplegia/paraparesis (HSP) type 15 (AR-SPG15) and type 11 (AR-SPG11), respectively. We previously have reported that AR-SPG15-related ZFYVE26 mutations lead to autophagy defects with accumulation of immature autophagosomes. ZFYVE26 and SPG11 were found to be part of a complex including the AP5 (adaptor related protein complex 5) and to have a critical role in autophagic lysosomal reformation with identification of autophagic and lysosomal defects in cells with both AR-SPG15- and AR-SPG11-related mutations...
August 7, 2018: Autophagy
Gourango Pradhan, Rohini Shrivastva, Sangita Mukhopadhyay
Phagosome maturation is an important innate defense mechanism of macrophages against bacterial infections. The mycobacterial secretory protein kinase G (PknG), a serine/threonine kinase, is known to block phagosome-lysosome (P-L) fusion, and the kinase activity of PknG appears to be crucial for this. However, the detail mechanisms are not well understood. In the current study, we demonstrate that PknG of Mycobacterium sp interacts with the human Rab GTPase protein, Rab7l1, but not with other Rab proteins as well as factors like Rabaptin, Rabex5, PI3K3, Mon1a, Mon1b, early endosome autoantigen 1, and LAMP2 that are known to play crucial roles in P-L fusion...
July 23, 2018: Journal of Immunology: Official Journal of the American Association of Immunologists
Lars Langemeyer, Florian Fröhlich, Christian Ungermann
Eukaryotic cells maintain a highly organized endolysosomal system. This system regulates the protein and lipid content of the plasma membrane, it participates in the intracellular quality control machinery and is needed for the efficient removal of damaged organelles. This complex network comprises an endosomal membrane system that feeds into the lysosomes, yet also allows recycling of membrane proteins, and probably lipids. Moreover, lysosomal degradation provides the cell with macromolecules for further growth...
July 16, 2018: Trends in Cell Biology
Xinli Ma, Kai Liu, Jian Li, Huanhuan Li, Jun Li, Yingfang Liu, Chonglin Yang, Huanhuan Liang
Endosomal transport represents the primary mode for intracellular trafficking and signaling transduction, and thus has to be tightly controlled. The molecular processes controlling the endosomal positioning utilizeseveral large protein complexes, one of which contains the small GTPase Rab7, Rab interacting lysosomal protein (RILP) and oxysterol binding protein related protein 1 (ORP1L). Rab7 is known to interact with RILP through a canonical binding site termed theeffector-interacting switch region, but it is not clear how Rab7 interacts with ORP1L, limiting our understanding of the overall process...
July 16, 2018: Journal of Biological Chemistry
Viktor Karlovich Lund, Kenneth Lindegaard Madsen, Ole Kjaerulff
Rab2 is a conserved Rab GTPase with a well-established role in secretory pathway function and phagocytosis. Here we demonstrate that Drosophila Rab2 is recruited to late endosomal membranes, where it controls the fusion of LAMP-containing biosynthetic carriers and lysosomes to late endosomes. In contrast, the lysosomal GTPase Gie/Arl8 is only required for late endosome-lysosome fusion, but not for the delivery of LAMP to the endocytic pathway. We also find that Rab2 is required for the fusion of autophagosomes to the endolysosomal pathway, but not for the biogenesis of lysosome-related organelles...
June 25, 2018: Autophagy
Azure Yarbrough, Katherine Maringer, Entsar J Saheb, Sanaa Jawed, John Bush
Rab GTPases are essential regulators of many cellular processes and play an important role in downstream signaling vital to proper cell function. We sought to elucidate the role of novel D. discoideum GTPase RabS. Cell lines over-expressing DdRabS and expressing DdRabS N137I (dominant negative (DN)) proteins were generated, and it was determined that DdRabS localized to endosomes, ER-Golgi membranes, and the contractile vacuole system. It appeared to function in vesicular trafficking, and the secretion of lysosomal enzymes...
May 28, 2018: Biology
Keith Ireton, Hoan Van Ngo, Manmeet Bhalla
Many microbial pathogens co-opt or perturb host membrane trafficking pathways. This review covers recent examples in which microbes interact with host exocytosis, the fusion of intracellular vesicles with the plasma membrane. The bacterial pathogens Listeria monocytogenes and Staphylococcus aureus subvert recycling endosomal pathways of exocytosis in order to induce their entry into human cells. By contrast, entry of the protozoan pathogen Trypanosoma cruzi or the virus adenovirus into host cells involves exploitation of lysosomal exocytosis...
August 2018: Cellular Microbiology
Yun-Na Zhang, Ya-Yun Liu, Fu-Chuan Xiao, Chun-Chun Liu, Xiao-Dong Liang, Jing Chen, Jing Zhou, Abdul Sattar Baloch, Lin Kan, Bin Zhou, Hua-Ji Qiu
The members of Flaviviridae utilize several endocytic pathways to enter a variety of host cells. Our previous work showed that classical swine fever virus (CSFV) enters porcine kidney (PK-15) cells through a clathrin-dependent pathway that requires Rab5 and Rab7. The entry mechanism for CSFV into other cell lines remains unclear, for instance, porcine alveolar macrophages (3D4/21 cells). More importantly, the trafficking of CSFV within endosomes controlled by Rab GTPases is unknown in 3D4/21 cells. In this study, entry and postinternalization of CSFV were analyzed using chemical inhibitors, RNA interference, and dominant-negative (DN) mutants...
August 1, 2018: Journal of Virology
Emi Ito, Kazuo Ebine, Seung-Won Choi, Sakura Ichinose, Tomohiro Uemura, Akihiko Nakano, Takashi Ueda
RAB5 is a key regulator of endosomal functions in eukaryotic cells. Plants possess two different RAB5 groups, canonical and plant-unique types, which act via unknown counteracting mechanisms. Here, we identified an effector molecule of the plant-unique RAB5 in Arabidopsis thaliana , ARA6, which we designated PLANT-UNIQUE RAB5 EFFECTOR 2 (PUF2). Preferential colocalization with canonical RAB5 on endosomes and genetic interaction analysis indicated that PUF2 coordinates vacuolar transport with canonical RAB5, although PUF2 was identified as an effector of ARA6...
May 11, 2018: ELife
Samual C Allgood, M Ramona Neunuebel
Bacterial pathogens have developed a wide range of strategies to survive within human cells. A number of pathogens multiply in a vacuolar compartment, whereas others can rupture the vacuole and replicate in the host cytosol. A common theme among many bacterial pathogens is the use of specialised secretion systems to deliver effector proteins into the host cell. These effectors can manipulate the host's membrane trafficking pathways to remodel the vacuole into a replication-permissive niche and prevent degradation...
July 2018: Cellular Microbiology
Emily K Herman, Moazzam Ali, Mark C Field, Joel B Dacks
Endocytosis is a crucial process in eukaryotic cells. The GTPases Rab 5, 21 and 22 that mediate endocytosis are ancient eukaryotic features and all available evidence suggests retained conserved function. In animals and fungi, these GTPases are regulated in part by proteins possessing Vps9 domains. However, the diversity, evolution and functions of Vps9 proteins beyond animals or fungi are poorly explored. Here we report a comprehensive analysis of the Vps9 family of GTPase regulators, combining molecular evolutionary data with functional characterization in the non-opisthokont model organism Trypanosoma brucei...
July 2018: Traffic
Noémie Scheidel, Julie Kennedy, Oliver E Blacque
Primary cilium structure and function relies on control of ciliary membrane homeostasis, regulated by membrane trafficking processes that deliver and retrieve ciliary components at the periciliary membrane. However, the molecular mechanisms controlling ciliary membrane establishment and maintenance, especially in relation to endocytosis, remain poorly understood. Here, using Caenorhabditis elegans , we describe closely linked functions for early endosome (EE) maturation factors RABS-5 (Rabenosyn-5) and VPS-45 (VPS45) in regulating cilium length and morphology, ciliary and periciliary membrane volume, and ciliary signalling-related sensory behaviour...
May 2, 2018: EMBO Journal
Lorena Pizarro, Meirav Leibman-Markus, Silvia Schuster, Maya Bar, Tal Meltz, Adi Avni
Plants recognize microbial/pathogen associated molecular patterns (MAMP/PAMP) through pattern recognition receptors (PRRs) triggering an immune response against pathogen progression. MAMP/PAMP triggered immune response requires PRR endocytosis and trafficking for proper deployment. LeEIX2 is a well-known Solanum lycopersicum RLP-PRR, able to recognize and respond to the fungal MAMP/PAMP ethylene-inducing xylanase (EIX), and its function is highly dependent on intracellular trafficking. Identifying protein machinery components regulating LeEIX2 intracellular trafficking is crucial to our understanding of LeEIX2 mediated immune responses...
2018: Frontiers in Plant Science
Kodai Takemoto, Kazuo Ebine, Jana Christin Askani, Falco Krüger, Zaida Andrés Gonzalez, Emi Ito, Tatsuaki Goh, Karin Schumacher, Akihiko Nakano, Takashi Ueda
Membrane trafficking plays pivotal roles in various cellular activities and higher-order functions of eukaryotes and requires tethering factors to mediate contact between transport intermediates and target membranes. Two evolutionarily conserved tethering complexes, homotypic fusion and protein sorting (HOPS) and class C core vacuole/endosome tethering (CORVET), are known to act in endosomal/vacuolar transport in yeast and animals. Both complexes share a core subcomplex consisting of Vps11, Vps18, Vps16, and Vps33, and in addition to this core, HOPS contains Vps39 and Vps41, whereas CORVET contains Vps3 and Vps8...
March 6, 2018: Proceedings of the National Academy of Sciences of the United States of America
Naoki Minamino, Takehiko Kanazawa, Atsuko Era, Kazuo Ebine, Akihiko Nakano, Takashi Ueda
The RAB GTPase is an evolutionarily conserved machinery component of membrane trafficking, which is the fundamental system for cell viability and higher order biological functions. The composition of RAB GTPases in each organism is closely related to the complexity and organization of the membrane trafficking pathway, which has been developed uniquely to realize the organism-specific membrane trafficking system. Comparative genomics has suggested that terrestrialization and/or multicellularization were associated with the expansion of membrane trafficking pathways in green plants, which has yet to be validated in basal land plant lineages...
April 1, 2018: Plant & Cell Physiology
Natalie Kofler, Federico Corti, Felix Rivera-Molina, Yong Deng, Derek Toomre, Michael Simons
As a master regulator of endothelial cell function, vascular endothelial growth factor receptor-2 (VEGFR2) activates multiple downstream signaling pathways that are critical for vascular development and normal vessel function. VEGFR2 trafficking through various endosomal compartments modulates its signaling output. Accordingly, proteins that regulate the speed and direction by which VEGFR2 traffics through endosomes have been demonstrated to be particularly important for arteriogenesis. However, little is known about how these proteins control VEGFR2 trafficking and about the implications of this control for endothelial cell function...
March 30, 2018: Journal of Biological Chemistry
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