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Small GTPases

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https://www.readbyqxmd.com/read/28524815/anchoring-high-concentrations-of-syngap-at-postsynaptic-densities-via-liquid-liquid-phase-separation
#1
Menglong Zeng, Guanhua Bai, Mingjie Zhang
SynGAP, encoded by SYNGAP1, is a Ras/Rap GTPase activator specifically expressed in the nervous systems. SynGAP is one of the most abundant proteins in the postsynaptic densities (PSDs) of excitatory synapses and acts as a critical synaptic activity brake by tuning down synaptic GTPase activities. Mutations of SYNGAP1 have been frequently linked to brain disorders including intellectual disability, autisms, and seizure. SynGAP has been shown to undergo fast dispersions from synapses in response to stimulations, a strategy that neurons use to control the specific activities of the enzyme within the tiny, semi-open compartments in dendritic spines...
May 19, 2017: Small GTPases
https://www.readbyqxmd.com/read/28524754/arf-gtpase-interplay-with-rho-gtpases-in-regulation-of-the-actin-cytoskeleton
#2
Vikash Singh, Anthony C Davidson, Peter J Hume, Daniel Humphreys, Vassilis Koronakis
The Arf and Rho subfamilies of small GTPases are nucleotide-dependent molecular switches that act as master regulators of vesicular trafficking and the actin cytoskeleton organization. Small GTPases control cell processes with high fidelity by acting through distinct repertoires of binding partners called effectors. While we understand a great deal about how these GTPases act individually, relatively little is known about how they cooperate, especially in the control of effectors. This review highlights how Arf GTPases collaborate with Rac1 to regulate actin cytoskeleton dynamics at the membrane via recruiting and activating the Wave Regulatory Complex (WRC), a Rho effector that underpins lamellipodia formation and macropinocytosis...
May 19, 2017: Small GTPases
https://www.readbyqxmd.com/read/28521592/molecular-perturbation-strategies-to-examine-spatiotemporal-features-of-rho-gef-and-rho-gtpase-activity-in-living-cells
#3
Joachim Goedhart, Jakobus van Unen
Much of our current knowledge of Rho GTPase networks and the regulation by Rho guanine exchange factors (Rho GEFs) and Rho GTPase activating proteins (Rho GAPs) is based on population-based techniques. Over the last decades, technologies that enable single cell analysis with high spatial and temporal resolution have revealed that Rho GTPase activity in cells is regulated on second timescales and at submicrometer length scales. Therefore, perturbation methods with matching spatial and temporal resolution are crucial to further our understanding of Rho GTPase signaling...
May 19, 2017: Small GTPases
https://www.readbyqxmd.com/read/28498728/a-family-affair-a-ral-exocyst-centered-network-links-ras-rac-rho-signaling-to-control-cell-migration
#4
Giulia Zago, Marco Biondini, Jacques Camonis, Maria Carla Parrini
Cell migration is central to many developmental, physiologic and pathological processes, including cancer progression. The Ral GTPases (RalA and RalB) which act down-stream the Ras oncogenes, are key players in the coordination between membrane trafficking and actin polymerization. A major direct effector of Ral, the exocyst complex, works in polarized exocytosis and is at the center of multiple protein-protein interactions that support cell migration by promoting protrusion formation, front-rear polarization, and extra-cellular matrix degradation...
May 12, 2017: Small GTPases
https://www.readbyqxmd.com/read/28489965/evidence-for-the-subsynaptic-zone-as-a-preferential-site-for-chrn-recycling-at-neuromuscular-junctions
#5
Franziska Wild, Muzamil Majid Khan, Rüdiger Rudolf
Vertebrate skeletal muscle contraction is mediated by nicotinic acetylcholine receptors (CHRN). Endocytosis and recycling of CHRN regulate their proper abundance at nerve-muscle synapses, i.e. neuromuscular junctions. Recent work showed that RAB5 is essential for CHRN endocytosis. Here, using in vivo-imaging of endocytosed CHRN and RAB-GFP fusion proteins, we deliver evidence for differential effects of RAB5-GFP, RAB4-GFP, and RAB11-GFP on CHRN endocytosis. Furthermore, while newly endocytosed CHRN colocalized with RAB5-GFP over large stretches of muscle fibers, RAB4-GFP and RAB11-GFP colocalized with endocytosed CHRN almost exclusively at neuromuscular junctions...
May 10, 2017: Small GTPases
https://www.readbyqxmd.com/read/28489964/specific-activation-of-plekhg2-induced-serum-response-element-dependent-gene-transcription-by-four-and-a-half-lim-domains-fhl-1-but-not-fhl2-or-fhl3
#6
Masashi Nishikawa, Katsuya Sato, Shun Nakano, Hisashi Yamakawa, Takahiro Nagase, Hiroshi Ueda
PLEKHG2 is a Gβγ- and Gαs-dependent guanine nucleotide exchange factor for Rac1 and Cdc42 small GTPases and has been shown to mediate signaling pathways such as those for actin cytoskeletal reorganization and serum response element (SRE)-dependent gene transcription. We have shown that the four-and-a-half LIM domains (FHL) 1 acts as a positive regulator of PLEKHG2. Here, we evaluated the other FHL family members and found that the FHL1A specifically regulate the PLEKHG2 activity. Moreover, FHL1A further enhanced Gβγ- and PLEKHG2-induced SRE-dependent gene transcription, whereas FHL1A partially restored the attenuated PLEKHG2-induced SRE-dependent gene transcription by Gαs...
May 10, 2017: Small GTPases
https://www.readbyqxmd.com/read/28489961/the-role-of-exo70-in-exocytosis-and-beyond
#7
Yueyao Zhu, Bin Wu, Wei Guo
The exocyst complex mediates the tethering of secretory vesicles to the plasma membrane prior to SNARE-mediated membrane fusion. Recent studies have implicated the exocyst in a wide range of cellular processes. Particularly, research on the Exo70 subunit of the complex has linked the function of the exocyst in exocytosis to cell adhesion, migration and invasion. In this review, we will discuss the recent work on how Exo70 regulates these cellular processes, and how small GTPases and kinases interact with Exo70 to orchestrate its function in exocytosis and cytoskeleton organization...
May 10, 2017: Small GTPases
https://www.readbyqxmd.com/read/28489960/swap70-is-a-universal-gef-like-adapter-for-tethering-actin-to-phagosomes
#8
Maksim V Baranov, Natalia H Revelo, Daniëlle R J Verboogen, Martin Ter Beest, Geert van den Bogaart
We recently identified a key role for SWAP70 as the tethering factor stabilizing F-actin filaments on the surface of phagosomes in human dendritic cells by interacting both with Rho-family GTPases and the lipid phosphatidylinositol (3,4)-bisphosphate. In this study, we aimed to investigate whether this role of SWAP70 was general among immune phagocytes. Our data reveal that SWAP70 is recruited to early phagosomes of macrophages and dendritic cells from both human and mouse. The putative inhibitor of SWAP70 sanguinarine blocked phagocytosis and F-actin polymerization, supporting a key role for SWAP70 in phagocytosis as demonstrated previously with knock-down...
May 10, 2017: Small GTPases
https://www.readbyqxmd.com/read/28471300/rab-gtpases-and-cell-division
#9
Paulius Gibieža, Rytis Prekeris
Cytokinesis is a complex cellular process that leads to a physical separation of two daughter cells. The key to a successful cytokinesis is a coordinated reorganization of cellular cytoskeleton and membrane trafficking pathways. Consequently, Rab GTPases recently emerged as major regulators of cellular division. Rabs belong to a superfamily of small monomeric GTPases that regulate a diverse array of cellular functions. Rabs in particular are well-established regulators of membrane transport and have been shown to mediate several membrane transport steps including vesicle formation, molecular motor-dependent vesicle transport and targeting of transport vesicles and organelles to their correct destinations...
May 4, 2017: Small GTPases
https://www.readbyqxmd.com/read/28471261/rab17-mediates-intermixing-of-phagocytosed-apoptotic-cells-with-recycling-endosomes
#10
Charles Yin, Dean Argintaru, Bryan Heit
Efferocytosis-the phagocytic removal of apoptotic cells-is required for preventing the presentation of apoptotic cell-derived antigens. This process is regulated by Rab17-dependent sorting of efferocytosed cargos from the phagolysosome to recycling endosomes. In this study we demonstrate that Rab17 is rapidly recruited to efferosomes, followed by migration of the efferosome to the cell center where it intermixes with lysosomes and undergoes Rab17-dependent vesiculation. These efferosome-derived vesicles then traffic in a Rab17-dependent manner to the cell periphery, where they transfer cargo to recycling endosomes...
May 4, 2017: Small GTPases
https://www.readbyqxmd.com/read/28471257/ras-ling-with-new-therapeutic-targets-for-metastasis
#11
Joshua A Mason, Zachary T Schafer
Successful cancer metastasis relies on the ability of cancer cells to survive independently of attachment to the extracellular matrix (ECM) and to overcome ECM-detachment-induced death programs. This can be accomplished through activating mutations in cellular oncogenes that subsequently lead to the inhibition of anoikis and to alterations in productive metabolism. One example of such an oncogene is Ras which is found to be mutated and hyperactivated in a variety of distinct cancers. Despite numerous studies on Ras, the precise molecular mechanisms that facilitate survival during ECM-detachment remain poorly understood...
May 4, 2017: Small GTPases
https://www.readbyqxmd.com/read/28463591/rab-gtpases-regulate-the-trafficking-of-channels-and-transporters-a-focus-on-cystic-fibrosis
#12
Carlos M Farinha, Paulo Matos
The amount of ion channels and transporters present at the plasma membrane is a crucial component of the overall regulation of ion transport. The number of channels present result from an intricate network of proteins that controls the late events of channel trafficking, such as endocytosis, recycling and targeting to lysosomal degradation. Small GTPases of the Rab family are key players in these processes thus contributing to regulation of fluid secretion and ion homeostasis. In epithelia, this involves mainly the balance between the chloride channel CFTR and the sodium channel ENaC, whose misfunction is a hallmark of cystic fibrosis - the commonest recessive disorder in Caucasians...
May 2, 2017: Small GTPases
https://www.readbyqxmd.com/read/28463543/roles-for-rab24-in-autophagy-and-disease
#13
Päivi Ylä-Anttila, Eeva-Liisa Eskelinen
Autophagy is an evolutionarily conserved degradation pathway for cells to maintain homeostasis, produce energy, degrade misfolded proteins and damaged organelles, and fight against intracellular pathogens. The process of autophagy entails the isolation of cytoplasmic cargo into double membrane bound autophagosomes that undergo maturation by fusion with endosomes and lysosomes in order to obtain degradation capacity. RAB proteins regulate intracellular vesicle trafficking events including autophagy. RAB24 is an atypical RAB protein that is required for the clearance of late autophagic vacuoles under basal conditions...
May 2, 2017: Small GTPases
https://www.readbyqxmd.com/read/28448737/involvement-of-arhgef10-gef-for-rhoa-in-rab6-rab8-mediating-membrane-traffic
#14
Satoshi Shibata, Yui Teshima, Kenta Niimi, Shinobu Inagaki
Small GTPases play crucial roles in the maintenance of a homeostatic environment and appropriate movements of the cell. In these processes, the direct or indirect interaction between distinct small GTPases could be required for regulating mutual signaling pathways. In our recent study, ARHGEF10, known as a guanine nucleotide exchange factor (GEF) for RhoA, was indicated to interact with Rab6A and Rab8A, which are known to function in the exocytotic pathway, and colocalized with these Rabs at exocytotic vesicles...
April 27, 2017: Small GTPases
https://www.readbyqxmd.com/read/28430047/arf-gaps-and-molecular-motors
#15
Ruibai Luo, Christine E Reed, Jeffrey A Sload, Linda Wordeman, Paul A Randazzo, Pei-Wen Chen
Arf GTPase-activating proteins (Arf GAPs) were first identified as regulators of the small GTP-binding proteins ADP-ribosylation factors (Arfs). The Arf GAPs are a large family of proteins in metazoans, outnumbering the Arfs that they regulate. The members of the Arf GAP family have complex domain structures and some have been implicated in particular cellular functions, such as cell migration, or with particular pathologies, such as tumor invasion and metastasis. The specific effects of Arfs sometimes depend on the Arf GAP involved in their regulation...
April 21, 2017: Small GTPases
https://www.readbyqxmd.com/read/28410007/key-roles-of-arf-small-g-proteins-and-biosynthetic-trafficking-for-animal-development
#16
Francisco F Rodrigues, Tony J C Harris
Although biosynthetic trafficking can function constitutively, it also functions specifically for certain developmental processes. These processes require either a large increase to biosynthesis or the biosynthesis and targeted trafficking of specific players. We review the conserved molecular mechanisms that direct biosynthetic trafficking, and discuss how their genetic disruption affects animal development. Specifically, we consider Arf small G proteins, such as Arf1 and Sar1, and their coat effectors, COPI and COPII, and how these proteins promote biosynthetic trafficking for cleavage of the Drosophila embryo, the growth of neuronal dendrites and synapses, extracellular matrix secretion for bone development, lumen development in epithelial tubes, notochord and neural tube development, and ciliogenesis...
April 14, 2017: Small GTPases
https://www.readbyqxmd.com/read/28394692/exploring-the-iceberg-prospects-of-coordinated-myosin-v-and-actin-assembly-functions-in-transport-processes
#17
Tobias Welz, Eugen Kerkhoff
Spir actin nucleators and myosin V motor proteins were recently discovered to coexist in a protein complex. The direct interaction allows the coordinated activation of actin motor proteins and actin filament track generation at vesicle membranes. By now the cooperation of myosin V (MyoV) motors and Spir actin nucleation function has only been shown in the exocytic transport of Rab11 vesicles in metaphase mouse oocytes. Next to Rab11, myosin V motors however interact with a variety of Rab GTPases including Rab3, Rab8 and Rab10...
April 10, 2017: Small GTPases
https://www.readbyqxmd.com/read/28362242/arf-gaps-a-family-of-proteins-with-disparate-functions-that-converge-on-a-common-structure-the-integrin-adhesion-complex
#18
Teresa Vitali, Sofia Girald-Berlingeri, Paul A Randazzo, Pei-Wen Chen
ADP-ribosylation factors (Arfs) are members of the Ras GTPase superfamily. The function of Arfs is dependent on GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs), which allow Arfs to cycle between the GDP-bound and GTP-bound forms. Arf GAPs have been shown to be present in integrin adhesion complexes, which include focal adhesions. Integrin adhesion complexes are composed of integrins, scaffolding proteins and signaling proteins and regulate cell proliferation, survival, differentiation and migration...
March 31, 2017: Small GTPases
https://www.readbyqxmd.com/read/28350208/polarity-establishment-by-cdc42-key-roles-for-positive-feedback-and-differential-mobility
#19
Benjamin Woods, Daniel J Lew
Cell polarity is fundamental to the function of most cells. The evolutionarily conserved molecular machinery that controls cell polarity is centered on a family of GTPases related to Cdc42. Cdc42 becomes activated and concentrated at polarity sites, but studies in yeast model systems led to controversy on the mechanisms of polarization. Here we review recent studies that have clarified how Cdc42 becomes polarized in yeast. On one hand, findings that appeared to support a key role for the actin cytoskeleton and vesicle traffic in polarity establishment now appear to reflect the action of stress response pathways induced by cytoskeletal perturbations...
March 28, 2017: Small GTPases
https://www.readbyqxmd.com/read/28328290/cross-talk-between-rho-gtpases-and-pi3k-in-the-neutrophil
#20
Barry McCormick, Julia Y Chu, Sonja Vermeren
Neutrophils are short-lived, abundant peripheral blood leukocytes that provide a first line of defense against bacterial and fungal infections while also being a key part of the inflammatory response. Chemokines induce neutrophil recruitment to inflammatory sites, where neutrophils perform several diverse functions that are aimed at fighting infections. Neutrophil effector functions are tightly regulated processes that are governed by an array of intracellular signaling pathways and initiated by receptor-ligand binding events...
March 22, 2017: Small GTPases
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