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Small GTPases

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https://www.readbyqxmd.com/read/27898263/genetic-alterations-affecting-gtpases-and-t-cell-receptor-signaling-in-peripheral-t-cell-lymphomas
#1
Rebecca L Boddicker, Gina L Razidlo, Andrew L Feldman
Peripheral T-cell lymphomas (PTCLs) are rare, heterogeneous tumors with poor response to standard therapy and few targeted treatments available. The identification of mutations in the T-cell receptor (TCR) signaling pathway that either directly or indirectly affect Ras- and Rho-family GTPases is an emerging theme across PTCL subtypes. This review summarizes the role of GTPases in TCR signaling and highlights the constellation of mutations in this pathway among PTCLs. In particular, focus is given to the functional impact of the mutations and opportunities for targeted therapy...
November 29, 2016: Small GTPases
https://www.readbyqxmd.com/read/27880081/an-emerging-role-for-iqgap1-in-tight-junction-control
#2
Barbara E Tanos, Charles Yeaman, Enrique Rodriguez-Boulan
IQGAP1 is a scaffold protein involved in the assembly of adherens junctions. Our work has recently revealed a novel role for IQGAP1 in the regulation of tight junctions (TJ) through differential recruitment of claudins to the nascent TJ. Here, we discuss the potential mechanisms of this regulation, including IQGAP1 effects on CDC42, and IQGAP1 interactions with sorting/trafficking molecules (e.g. Exo70). Given the many roles of IQGAP1 and the large number of interacting partners, we focus our discussion of these functions in the context of junction formation, trafficking, growth factor signaling and cancer...
November 23, 2016: Small GTPases
https://www.readbyqxmd.com/read/27880072/oncogenic-kras-and-the-egfr-loop-in-pancreatic-carcinogenesis-a-connection-to-licensing-nodes
#3
Christian Schneeweis, Matthias Wirth, Dieter Saur, Maximilian Reichert, Günter Schneider
EGFR signaling has a critical role in oncogenic KRAS-driven tumorigenesis of the pancreas, whereas it is dispensable in other organs. The complex signaling network engaged by oncogenic KRAS and its modulation by EGFR signaling, remains incompletely understood. In order to study early signaling events activated by oncogenic KRAS in the pancreas, we recently developed a novel model system based on murine primary pancreatic epithelial cells enabling the time-specific expression of mutant Kras(G12D) from its endogenous promoter...
November 23, 2016: Small GTPases
https://www.readbyqxmd.com/read/27875100/the-small-gtpase-ral-orchestrates-mvb-biogenesis-and-exosome-secretion
#4
Vincent Hyenne, Michel Labouesse, Jacky G Goetz
Extracellular vesicles are novel mediators of cell-cell communication. They are present in all species and involved in physiological and pathological processes. One class of extracellular vesicles, the exosomes, originate from an endosomal compartment, the MultiVesicular Body (MVB), and are released from the cell upon fusion of the MVB with the plasma membrane. Although different molecular mechanisms have been associated with MVB biogenesis and exosome secretion, how they coordinate remains poorly documented...
November 22, 2016: Small GTPases
https://www.readbyqxmd.com/read/27875099/the-rhob-small-gtpase-in-physiology-and-disease
#5
Francisco M Vega, Anne J Ridley
RhoB is a Rho family GTPase that is highly similar to RhoA and RhoC, yet has distinct functions in cells. Its unique C-terminal region is subject to specific post-translational modifications that confer different localization and functions to RhoB. Apart from the common role with RhoA and RhoC in actin organization and cell migration, RhoB is also implicated in a variety of other cellular processes including membrane trafficking, cell proliferation, DNA-repair and apoptosis. RhoB is not an essential gene in mice, but it is implicated in several physiological and pathological processes...
November 22, 2016: Small GTPases
https://www.readbyqxmd.com/read/27854154/small-gtpases-in-c-elegans-metabolism
#6
Daniel Z Bar, Chayki Charar, Yosef Gruenbaum
The mechanistic target of rapamycin (mTOR) is an evolutionary conserved protein with a serine/threonine kinase activity that regulates cell growth, proliferation, motility, survival, protein synthesis, autophagy and transcription. It is embedded in 2 large protein complexes: mTORC1 and mTORC2. Regulation of specific mTOR pathway functions depends on multiple GTPases, that act either as regulators of mTOR protein complexes, coupling energy availability with mTORC1 activity, or as downstream effectors of both mTORC1 and mTORC2...
November 17, 2016: Small GTPases
https://www.readbyqxmd.com/read/27849131/spatial-rho-regulation-molecular-mechanisms-controlling-the-gap-protein-dlc3
#7
Janina Hendrick, Monilola A Olayioye
The spatial regulation of cellular Rho signaling by GEF and GAP proteins and the molecular mechanisms controlling the Rho regulators themselves are still incompletely understood. We previously reported that the poorly characterized RhoGAP protein DLC3 localizes to cell-cell adhesions and Rab8-positive membrane tubules. However, it was unclear how DLC3 is targeted to these subcellular sites to execute its functions. In our recent work, protein partners of DLC3 were identified by mass spectrometry, identifying the basolateral polarity protein Scribble as a scaffold for DLC3 at cell-cell contacts...
November 16, 2016: Small GTPases
https://www.readbyqxmd.com/read/27768524/c9orf72-plays-a-central-role-in-rab-gtpase-dependent-regulation-of-autophagy
#8
Christopher P Webster, Emma F Smith, Andrew J Grierson, Kurt J De Vos
A GGGGCC hexanucleotide repeat expansion in the first intron of the C9orf72 gene is the most common genetic defect associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (C9ALS/FTD). Haploinsufficiency and a resulting loss of C9orf72 protein function has been suggested as a possible pathogenic mechanism in C9ALS/FTD. C9ALS/FTD patients exhibit specific ubiquitin and p62/sequestosome-1 positive but TDP-43 negative inclusions in the cerebellum and hippocampus, indicating possible autophagy deficits in these patients...
October 21, 2016: Small GTPases
https://www.readbyqxmd.com/read/27768516/rho-gtpases-in-mammalian-spinal-neural-tube-closure
#9
Ana Rolo, Sarah Escuin, Nicholas D E Greene, Andrew J Copp
Neural tube closure is an important morphogenetic event that involves dramatic reshaping of both neural and non-neural tissues. Rho GTPases are key cytoskeletal regulators involved in cell motility and in several developmental processes, and are thus expected to play pivotal roles in neurulation. Here, we discuss 2 recent studies that shed light on the roles of distinct Rho GTPases in different tissues during neurulation. RhoA plays an essential role in regulating actomyosin dynamics in the neural epithelium of the elevating neural folds, while Rac1 is required for the formation of cell protrusions in the non-neural surface ectoderm during neural fold fusion...
October 21, 2016: Small GTPases
https://www.readbyqxmd.com/read/27763815/diverted-recycling-shigella-subversion-of-rabs
#10
Noelia Lopez Montero, Jost Enninga
Small GTPases of the Rab protein family control intracellular vesicular trafficking to allow their communication and maintenance. It is a common strategy for intracellular bacteria to exploit these pathways to shape their respective niches for survival. The subversion of Rabs for the generation of an intracellular environment favoring the pathogen has been described almost exclusively for intracellular bacteria that reside within bacterial containing vacuoles (BCVs). However, less is known about Rab subversion for bacteria that rupture the BCV to reach the host cytoplasm...
October 20, 2016: Small GTPases
https://www.readbyqxmd.com/read/27763811/small-gtpase-proteins-in-macroautophagy
#11
Shu Yang, Anne Rosenwald
Macroautophagy, a highly conserved process in eukaryotic cells, is initiated in response to stress, especially nutrient starvation. Macroautophagy helps cells survive by engulfing proteins and organelles into an unusual double-membraned structure called the autophagosome, which then fuses with the lysosome. Upon degradation of the engulfed contents, the building blocks are recycled for synthesis of new macromolecules. Recent work has demonstrated that construction of the autophagosome requires a variety of small GTPases in variations of their normal roles in membrane traffic...
October 20, 2016: Small GTPases
https://www.readbyqxmd.com/read/27754752/rhoa-controls-retinoid-signaling-by-rock-dependent-regulation-of-retinol-metabolism
#12
Alberto García-Mariscal, Karine Peyrollier, Astrid Basse, Esben Pedersen, Ralph Rühl, Jolanda van Hengel, Cord Brakebusch
The ubiquitously expressed small GTPase RhoA is essential for embryonic development and mutated in different cancers. Functionally, it is well described as a regulator of the actin cytoskeleton, but its role in gene regulation is less understood. Using primary mouse keratinocytes with a deletion of the RhoA gene, we have now been exploring how the loss of RhoA affects gene expression. Performing transcription factor reporter assays, we found a significantly decreased activity of a RAR luciferase reporter in RhoA-null keratinocytes...
October 18, 2016: Small GTPases
https://www.readbyqxmd.com/read/27754746/the-distinct-traits-of-extracellular-vesicles-generated-by-transformed-cells
#13
Marc A Antonyak, Richard A Cerione
Intercellular communication mediated by extracellular vesicles (EVs), membrane-enclosed packages released by cells, plays important roles in several physiological and pathological settings. Moreover, EVs have been shown to contain molecular signatures that reflect their cell of origin, raising the possibility that EV cargo could potentially be used to diagnose disease. However, for this to occur, a better understanding of the differences between EVs generated by normal and diseased cells is needed. We recently discovered that the content and function of one major class of EVs, microvesicles (MVs), changes upon the induction of oncogenic transformation...
October 18, 2016: Small GTPases
https://www.readbyqxmd.com/read/27754741/arf6-and-its-zeb1-epb41l5-mesenchymal-axis-are-required-for-both-mesenchymal-and-amoeboid-type-invasion-of-cancer-cells
#14
Haruka Handa, Ari Hashimoto, Shigeru Hashimoto, Hisataka Sabe
Modes of cancer invasion interchange between the mesenchymal type and amoeboid type in response to the microenvironment, in which RhoA and Rac1 are selectively required to perform different modes of actin-cytoskeletal remodeling. Membrane remodeling is another integral part of invasion. Arf6 regulates the recycling of molecules at the cell periphery, and is often overexpressed in malignant cancers together with its effector AMAP1/ASAP1/DDEF1. This pathway promotes mesenchymal-type invasion when AMAP1 binds to EPB41L5, a mesenchymal-specific protein induced by ZEB1...
October 18, 2016: Small GTPases
https://www.readbyqxmd.com/read/27715492/connecting-g-protein-signaling-to-chemoattractant-mediated-cell-polarity-and-cytoskeletal-reorganization
#15
Youtao Liu, Jesus Lacal, Richard A Firtel, Arjan Kortholt
The directional movement towards extracellular chemical gradients, a process called chemotaxis, is an important property of cells. Central to eukaryotic chemotaxis is the molecular mechanism by which chemoattractant-mediated activation of G-protein coupled receptors (GPCRs) induces symmetry breaking in the activated downstream signaling pathways. Studies with mainly Dictyostelium and mammalian neutrophils as experimental systems have shown that chemotaxis is mediated by a complex network of signaling pathways...
October 7, 2016: Small GTPases
https://www.readbyqxmd.com/read/27690729/endothelin-1-receptor-drives-invadopodia-exploiting-how-%C3%AE-arrestin-1-guides-the-way
#16
Anna Bagnato, Laura Rosanò
Metastatization is a complex multistep process requiring fine-tuned regulated cytoskeleton re-modeling, mediated by the cross-talk of actin with interacting partners, such as the Rho GTPases. Our expanding knowledge of invadopodia, small invasive membrane protrusions composed of a core of F-actin, actin regulators and actin-binding proteins, and hotspots for secretion of extracellular matrix (ECM) proteinases, contributes to clarify critical steps of the metastatic program. Growth factor receptors and their intermediate signaling molecules, along with matrix adhesion and rigidity, pH and hypoxia, act as drivers of cytoskeleton changes and invadopodia formation...
October 3, 2016: Small GTPases
https://www.readbyqxmd.com/read/27687567/nuf-and-rip11-requirement-for-polarity-determinant-recycling-during-drosophila-development
#17
Francisco J Calero-Cuenca, Sol Sotillos
A tight relationship between apico-basal polarity and trafficking is essential for epithelial physiology and tissue homeostasis. Recent studies have described how some Rab GTPases, key components of the intracellular traffic machinery, contribute to the establishment of cell polarity in vertebrates. We have demonstrated a novel connection between cell polarity and trafficking: in Drosophila epithelia, the apical determinant aPKC is recycled via Rab11-Nuf-recycling endosomes to maintain cell polarity. Furthermore, the phosphorylation of Nuf by aPKC allows aPKC to control the sub-cellular localization of Nuf and its own membrane accumulation...
September 29, 2016: Small GTPases
https://www.readbyqxmd.com/read/27687479/rab3a-and-rab10-are-regulators-of-lysosome-exocytosis-and-plasma-membrane-repair
#18
Otilia V Vieira
Disruption of the cell plasma membrane can occur due to mechanical damage, pore forming toxins, etc. Resealing or plasma membrane repair (PMR) is the emergency response required for cell survival. It is triggered by Ca(2+) entering through the disruption, causing organelles such as lysosomes located underneath the plasma membrane to fuse rapidly with the adjacent plasma membrane. We have recently identified some of the molecular traffic machinery that is involved in this vital process. Specifically, we showed that 2 members of the Rab family of small GTPases, Rab3a and Rab10, are essential for lysosome exocytosis and PMR in cells challenged with a bacterial toxin, streptolysin-O (SLO)...
September 29, 2016: Small GTPases
https://www.readbyqxmd.com/read/27676292/rhob-expression-controls-the-activity-of-serine-threonine-protein-phosphatase-pp2a-to-modulate-mesenchymal-phenotype-and-invasion-in-non-small-cell-lung-cancers
#19
Olivier Calvayrac, Anne Pradines, Gilles Favre
Metastatic dissemination is the cause of death in the vast majority of cancers, including lung cancers. In order to metastasize, tumor cells must undergo a well-known series of changes, however the molecular details of how they manage to overcome the barriers at each stage remain incomplete. One critical step is acquiring the ability to migrate through the extracellular matrix. Loss of expression of the RAS-related small GTPase RHOB is a common feature of lung cancer progression, and we recently reported that this induces an epithelial-to-mesenchymal transition (EMT) that is dependent on SLUG overexpression and E-Cadherin inhibition and is characterized by 3-dimensional cell shape reorganization and the increased invasiveness of bronchial cells...
September 27, 2016: Small GTPases
https://www.readbyqxmd.com/read/27657886/regulation-of-rho-gtpases-from-the-lateral-sides-of-migrating-cells
#20
Liang Zhang, Jeffrey L Wrana
Migratory polarity and epithelial polarity share many common regulatory mechanisms. Rho GTPases play a key role in modulating cell polarity, which in migrating cells has been conventionally studied along the solitary front-rear axis. In recent work, we discovered that Prickle1 (Pk1), a core com-ponent of planar cell polarity (PCP) signaling, mediates a novel lateral signaling pathway that coordinates multi-axial protrusive activities from the lateral cortex of migrating cancer cells. We identified that Arhgap21 and 23 are essential effectors of Pk1, and that lateral signaling regulates RhoA, actomyosin and focal adhesion dynamics...
September 22, 2016: Small GTPases
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