scholarly journals Identification and characterization of a new isoform of small GTPase RhoE

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Yuan Dai ◽  
Weijia Luo ◽  
Xiaojing Yue ◽  
Wencai Ma ◽  
Jing Wang ◽  
...  
Keyword(s):  
Rho Gtpase ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Biological Functions ◽  
Coding Region ◽  
Alternative Translation ◽  
Rho Family ◽  
Binding Capability ◽  
Identification And Characterization

Abstract The Rho family of GTPases consists of 20 members including RhoE. Here, we discover the existence of a short isoform of RhoE designated as RhoEα, the first Rho GTPase isoform generated from alternative translation. Translation of this new isoform is initiated from an alternative start site downstream of and in-frame with the coding region of the canonical RhoE. RhoEα exhibits a similar subcellular distribution while its protein stability is higher than RhoE. RhoEα contains binding capability to RhoE effectors ROCK1, p190RhoGAP and Syx. The distinct transcriptomes of cells with the expression of RhoE and RhoEα, respectively, are demonstrated. The data propose distinctive and overlapping biological functions of RhoEα compared to RhoE. In conclusion, this study reveals a new Rho GTPase isoform generated from alternative translation. The discovery provides a new scope of understanding the versatile functions of small GTPases and underlines the complexity and diverse roles of small GTPases.

scholarly journals PseudoGTPase domains in p190RhoGAP proteins: a mini-review

2018 ◽  
Vol 46 (6) ◽  
pp. 1713-1720 ◽  
Author(s):  
Amy L. Stiegler ◽  
Titus J. Boggon
Keyword(s):  
Family Members ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Signaling Proteins ◽  
New Family ◽  
Gtpase Activating Proteins ◽  
Rho Family ◽  
Biochemical Analyses ◽  
Catalytic Cleft

Pseudoenzymes generally lack detectable catalytic activity despite adopting the overall protein fold of their catalytically competent counterparts, indeed ‘pseudo’ family members seem to be incorporated in all enzyme classes. The small GTPase enzymes are important signaling proteins, and recent studies have identified many new family members with noncanonical residues within the catalytic cleft, termed pseudoGTPases. To illustrate recent discoveries in the field, we use the p190RhoGAP proteins as an example. p190RhoGAP proteins (ARHGAP5 and ARHGAP35) are the most abundant GTPase activating proteins for the Rho family of small GTPases. These are key regulators of Rho signaling in processes such as cell migration, adhesion and cytokinesis. Structural biology has complemented and guided biochemical analyses for these proteins and has allowed discovery of two cryptic pseudoGTPase domains, and the re-classification of a third, previously identified, GTPase-fold domain as a pseudoGTPase. The three domains within p190RhoGAP proteins illustrate the diversity of this rapidly expanding pseudoGTPase group.

scholarly journals Co-ordinated Ras and Rac activity shapes macropinocytic cups and enables phagocytosis of geometrically diverse bacteria

2019 ◽  
Author(s):  
Catherine M. Buckley ◽  
Henderikus Pots ◽  
Aurelie Gueho ◽  
Ben A. Phillips ◽  
Bernd Gilsbach ◽  
...  
Keyword(s):  
Dictyostelium Discoideum ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Extracellular Material ◽  
Multidomain Protein ◽  
Complex Shapes ◽  
Rho Family ◽  
Phagocytic Cups ◽  
Interior Domain ◽  
Professional Phagocyte

AbstractEngulfment of extracellular material by phagocytosis or macropinocytosis depends on the ability of cells to generate specialised cup shaped protrusions. To effectively capture and internalise their targets, these cups are organised into a ring or ruffle of actin-driven protrusion encircling a non-protrusive interior domain. These functional domains depend on the combined activities of multiple Ras and Rho family small GTPases, but how their activities are integrated and differentially regulated over space and time is unknown. Here, we show that the amoeba Dictyostelium discoideum coordinates Ras and Rac activity using the multidomain protein RGBARG (RCC1, RhoGEF, BAR and RasGAP-containing protein). We find RGBARG uses a tripartite mechanism of Ras, Rac and phospholipid interactions to localise at the protruding edge and interface with the interior of both macropinocytic and phagocytic cups. There, RGBARG shapes the protrusion by driving Rac activation at the rim whilst suppressing expansion of the active Ras interior domain. Consequently, cells lacking RGBARG form enlarged, flat interior domains unable to generate large macropinosomes. During phagocytosis, we find that disruption of RGBARG causes a geometry-specific defect in engulfing rod-shaped bacteria and ellipsoidal beads. This demonstrates the importance of co-ordinating small GTPase activities during engulfment of more complex shapes and thus the full physiological range of microbes, and how this is achieved in a model professional phagocyte.

scholarly journals Grit, a GTPase-Activating Protein for the Rho Family, Regulates Neurite Extension through Association with the TrkA Receptor and N-Shc and CrkL/Crk Adapter Molecules

2002 ◽  
Vol 22 (24) ◽  
pp. 8721-8734 ◽  
Author(s):  
Takeshi Nakamura ◽  
Misako Komiya ◽  
Kiyoaki Sone ◽  
Eiji Hirose ◽  
Noriko Gotoh ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Neuronal Cells ◽  
Small Gtpases ◽  
Actin Dynamics ◽  
Gtpase Activating Protein ◽  
Interacting Protein ◽  
High Affinity Receptor ◽  
Rho Family

ABSTRACT Neurotrophins are key regulators of the fate and shape of neuronal cells and act as guidance cues for growth cones by remodeling the actin cytoskeleton. Actin dynamics is controlled by Rho GTPases. We identified a novel Rho GTPase-activating protein (Grit) for Rho/Rac/Cdc42 small GTPases. Grit was abundant in neuronal cells and directly interacted with TrkA, a high-affinity receptor for nerve growth factor (NGF). Another pool of Grit was recruited to the activated receptor tyrosine kinase through its binding to N-Shc and CrkL/Crk, adapter molecules downstream of activated receptor tyrosine kinases. Overexpression of the TrkA-binding region of Grit inhibited NGF-induced neurite elongation. Further, we found some tendency for neurite promotion in full-length Grit-overexpressing PC12 cells upon NGF stimulation. These results suggest that Grit, a novel TrkA-interacting protein, regulates neurite outgrowth by modulating the Rho family of small GTPases.

scholarly journals A Ral GAP complex links PI 3-kinase/Akt signaling to RalA activation in insulin action

2011 ◽  
Vol 22 (1) ◽  
pp. 141-152 ◽  
Author(s):  
Xiao-Wei Chen ◽  
Dara Leto ◽  
Tingting Xiong ◽  
Genggeng Yu ◽  
Alan Cheng ◽  
...  
Keyword(s):  
Glucose Transporter ◽  
Critical Role ◽  
Inhibitory Effect ◽  
Small Gtpase ◽  
Regulatory Subunit ◽  
Hydrolysis Of ◽  
Identification And Characterization

Insulin stimulates glucose transport in muscle  and adipose tissue by translocation of glucose transporter 4 (GLUT4) to the plasma membrane. We previously reported that activation of the small GTPase RalA downstream of PI 3-kinase plays a critical role in this process by mobilizing the exocyst complex for GLUT4 vesicle targeting in adipocytes. Here we report the identification and characterization of a Ral GAP complex (RGC) that mediates the activation of RalA downstream of the PI 3-kinase/Akt pathway. The complex is composed of an RGC1 regulatory subunit and an RGC2 catalytic subunit (previously identified as AS250) that directly stimulates the guanosine triphosphate hydrolysis of RalA. Knockdown of RGC proteins leads to increased RalA activity and glucose uptake in adipocytes. Insulin inhibits the GAP complex through Akt2-catalyzed phosphorylation of RGC2 in vitro and in vivo, while activated Akt relieves the inhibitory effect of RGC proteins on RalA activity. The RGC complex thus connects PI 3-kinase/Akt activity to the transport machineries responsible for GLUT4 translocation.

scholarly journals Isolation and Characterization of Effector-Loop Mutants ofCDC42in Yeast

2001 ◽  
Vol 12 (5) ◽  
pp. 1239-1255 ◽  
Author(s):  
Amy S. Gladfelter ◽  
John J. Moskow ◽  
Trevin R. Zyla ◽  
Daniel J. Lew
Keyword(s):  
Cell Polarity ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Cytoskeletal Organization ◽  
Cell Behaviors ◽  
Isolation And Characterization ◽  
Starting Point ◽  
Effector Pathways

The highly conserved small GTPase Cdc42p is a key regulator of cell polarity and cytoskeletal organization in eukaryotic cells. Multiple effectors of Cdc42p have been identified, although it is unclear how their activities are coordinated to produce particular cell behaviors. One strategy used to address the contributions made by different effector pathways downstream of small GTPases has been the use of “effector-loop” mutants of the GTPase that selectively impair only a subset of effector pathways. We now report the generation and preliminary characterization of a set of effector-loop mutants ofSaccharomyces cerevisiae CDC42. These mutants define genetically separable pathways influencing actin or septin organization. We have characterized the phenotypic defects of these mutants and the binding defects of the encoded proteins to known yeast Cdc42p effectors in vitro. The results suggest that these effectors cannot account for the observed phenotypes, and therefore that unknown effectors exist that affect both actin and septin organization. The availability of partial function alleles of CDC42 in a genetically tractable system serves as a useful starting point for genetic approaches to identify such novel effectors.

scholarly journals Rho family GTPases control entry of Shigella flexneri into epithelial cells but not intracellular motility

1999 ◽  
Vol 112 (13) ◽  
pp. 2069-2080 ◽  
Author(s):  
J. Mounier ◽  
V. Laurent ◽  
A. Hall ◽  
P. Fort ◽  
M.F. Carlier ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Rho Gtpases ◽  
Actin Polymerization ◽  
Rho Gtpase ◽  
Shigella Flexneri ◽  
Intercellular Junctions ◽  
Small Gtpases ◽  
Comet Tail ◽  
Rho Family ◽  
Intracellular Motility

Shigella flexneri, an invasive bacterial pathogen, promotes formation of two cytoskeletal structures: the entry focus that mediates bacterial uptake into epithelial cells and the actin-comet tail that enables the bacteria to spread intracellularly. During the entry step, secretion of bacterial invasins causes a massive burst of subcortical actin polymerization leading the formation of localised membrane projections. Fusion of these membrane ruffles leads to bacterial internalization. Inside the cytoplasm, polar expression of the IcsA protein on the bacterial surface allows polymerization of actin filaments and their organization into an actin-comet tail leading to bacterial spread. The Rho family of small GTPases plays an essential role in the organization and regulation of cellular cytoskeletal structures (i.e. filopodia, lamellipodia, adherence plaques and intercellular junctions). We show here that induction of Shigella entry foci is controlled by the Cdc42, Rac and Rho GTPases, but not by RhoG. In contrast, actin-driven intracellular motility of Shigella does not require Rho GTPases. Therefore, Shigella appears to manipulate the epithelial cell cytoskeleton both by Rho GTPase-dependent and -independent processes.

scholarly journals Activation of STAT transcription factors by the Rho-family GTPases

2020 ◽  
Vol 48 (5) ◽  
pp. 2213-2227
Author(s):  
Jessica Corry ◽  
Helen R. Mott ◽  
Darerca Owen
Keyword(s):  
Transcription Factors ◽  
Rho Gtpase ◽  
Therapeutic Potential ◽  
Small Gtpases ◽  
Cellular Morphology ◽  
Invasion And Metastasis ◽  
Family Control ◽  
Signal Transducers ◽  
Downstream Effectors ◽  
Rho Family

The Rho-family of small GTPases are biological molecular switches that are best known for their regulation of the actin cytoskeleton. Through their activation and stimulation of downstream effectors, the Rho-family control pathways involved in cellular morphology, which are commonly activated in cancer cell invasion and metastasis. While this makes them excellent potential therapeutic targets, a deeper understanding of the downstream signalling pathways they influence will be required for successful drug targeting. Signal transducers and activators of transcription (STATs) are a family of transcription factors that are hyper-activated in most cancer types and while STATs are widely understood to be activated by the JAK family of kinases, many additional activators have been discovered. A growing number of examples of Rho-family driven STAT activation, largely of the oncogenic family members, STAT3 and STAT5, are being identified. Cdc42, Rac1, RhoA, RhoC and RhoH have all been implicated in STAT activation, contributing to Rho GTPase-driven changes in cellular morphology that lead to cell proliferation, invasion and metastasis. This highlights the importance and therapeutic potential of the Rho-family as regulators of non-canonical activation of STAT signalling.

scholarly journals RNA Interference Screening Identifies Novel Roles for RhoBTB1 and RhoBTB3 in Membrane Trafficking Events in Mammalian Cells

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1089 ◽  
Author(s):  
Maeve Long ◽  
Tilen Kranjc ◽  
Margaritha M. Mysior ◽  
Jeremy C. Simpson
Keyword(s):  
Rna Interference ◽  
Golgi Complex ◽  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Rho Gtpase ◽  
Family Members ◽  
Membrane Traffic ◽  
Small Gtpases ◽  
Endomembrane System ◽  
Rho Family

In the endomembrane system of mammalian cells, membrane traffic processes require a high degree of regulation in order to ensure their specificity. The range of molecules that participate in trafficking events is truly vast, and much attention to date has been given to the Rab family of small GTPases. However, in recent years, a role in membrane traffic for members of the Rho GTPase family, in particular Cdc42, has emerged. This prompted us to develop and apply an image-based high-content screen, initially focussing on the Golgi complex, using RNA interference to systematically perturb each of the 21 Rho family members and assess their importance to the overall organisation of this organelle. Analysis of our data revealed previously unreported roles for two atypical Rho family members, RhoBTB1 and RhoBTB3, in membrane traffic events. We find that depletion of RhoBTB3 affects the morphology of the Golgi complex and causes changes in the trafficking speeds of carriers operating at the interface of the Golgi and endoplasmic reticulum. In addition, RhoBTB3 was found to be present on these carriers. Depletion of RhoBTB1 was also found to cause a disturbance to the Golgi architecture, however, this phenotype seems to be linked to endocytosis and retrograde traffic pathways. RhoBTB1 was found to be associated with early endosomal intermediates, and changes in the levels of RhoBTB1 not only caused profound changes to the organisation and distribution of endosomes and lysosomes, but also resulted in defects in the delivery of two different classes of cargo molecules to downstream compartments. Together, our data reveal new roles for these atypical Rho family members in the endomembrane system.

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