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 Abl Kinases Regulate Actin Comet Tail Elongation via an N-WASP-Dependent Pathway

2005 ◽  
Vol 25 (20) ◽  
pp. 8834-8843 ◽  
Author(s):  
Elizabeth A. Burton ◽  
Timothy N. Oliver ◽  
Ann Marie Pendergast
Keyword(s):  
Host Cell ◽  
Actin Polymerization ◽  
Shigella Flexneri ◽  
Microbial Pathogens ◽  
Productive Infection ◽  
Cell Protein ◽  
Comet Tail ◽  
Abl Kinases ◽  
Molecular Machinery ◽  
Intracellular Motility

ABSTRACT Microbial pathogens have evolved diverse strategies to modulate the host cell cytoskeleton to achieve a productive infection and have proven instrumental for unraveling the molecular machinery that regulates actin polymerization. Here we uncover a mechanism for Shigella flexneri-induced actin comet tail elongation that links Abl family kinases to N-WASP-dependent actin polymerization. We show that the Abl kinases are required for Shigella actin comet tail formation, maximal intracellular motility, and cell-to-cell spread. Abl phosphorylates N-WASP, a host cell protein required for actin comet tail formation, and mutation of the Abl phosphorylation sites on N-WASP impairs comet tail elongation. Furthermore, we show that defective comet tail formation in cells lacking Abl kinases is rescued by activated forms of N-WASP. These data demonstrate for the first time that the Abl kinases play a role in the intracellular motility and intercellular dissemination of Shigella and uncover a new role for Abl kinases in the regulation of pathogen motility.

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 Rac1 links leading edge and uropod events through Rho and myosin activation during chemotaxis

Blood ◽  
2006 ◽  
Vol 108 (8) ◽  
pp. 2814-2820 ◽  
Author(s):  
Kersi N. Pestonjamasp ◽  
Carol Forster ◽  
Chunxiang Sun ◽  
Elisabeth M. Gardiner ◽  
Ben Bohl ◽  
...  
Keyword(s):  
Rho Gtpases ◽  
Actin Polymerization ◽  
Critical Role ◽  
Leading Edge ◽  
Feedback System ◽  
Small Gtpases ◽  
Human Neutrophils ◽  
Trailing Edge ◽  
Rac Gtpases ◽  
Rho Family

Abstract Chemotactic responsiveness is crucial to neutrophil recruitment to sites of infection. During chemotaxis, highly divergent cytoskeletal programs are executed at the leading and trailing edge of motile neutrophils. The Rho family of small GTPases plays a critical role in cell migration, and recent work has focused on elucidating the specific roles played by Rac1, Rac2, Cdc42, and Rho during cellular chemotaxis. Rac GTPases regulate actin polymerization and extension of the leading edge, whereas Rho GTPases control myosin-based contraction of the trailing edge. Rac and Rho signaling are thought to crosstalk with one another, and previous research has focused on mutual inhibition of Rac and Rho signaling during chemotaxis. Indeed, polarization of neutrophils has been proposed to involve the activity of a negative feedback system where Rac activation at the front of the cell inhibits local Rho activation, and vice versa. Using primary human neutrophils and neutrophils derived from a Rac1/Rac2-null transgenic mouse model, we demonstrate here that Rac1 (and not Rac2) is essential for Rho and myosin activation at the trailing edge to regulate uropod function. We conclude that Rac plays both positive and negative roles in the organization of the Rhomyosin “backness” program, thereby promoting stable polarity in chemotaxing neutrophils.

scholarly journals The Small GTPases Rho and Rac Are Required for the Establishment of Cadherin-dependent Cell–Cell Contacts

1997 ◽  
Vol 137 (6) ◽  
pp. 1421-1431 ◽  
Author(s):  
Vania M.M. Braga ◽  
Laura M. Machesky ◽  
Alan Hall ◽  
Neil A. Hotchin
Keyword(s):  
Cell Adhesion ◽  
Epithelial Cells ◽  
Active Form ◽  
Intercellular Junctions ◽  
Small Gtpases ◽  
Cell Contacts ◽  
Calcium Dependent ◽  
Dependent Cell ◽  
Rho Family ◽  
Cell Cell

Cadherins are calcium-dependent cell–cell adhesion molecules that require the interaction of the cytoplasmic tail with the actin cytoskeleton for adhesive activity. Because of the functional relationship between cadherin receptors and actin filament organization, we investigated whether members of the Rho family of small GTPases are necessary for cadherin adhesion. In fibroblasts, the Rho family members Rho and Rac regulate actin polymerization to produce stress fibers and lamellipodia, respectively. In epithelial cells, we demonstrate that Rho and Rac are required for the establishment of cadherin-mediated cell–cell adhesion and the actin reorganization necessary to stabilize the receptors at sites of intercellular junctions. Blocking endogenous Rho or Rac selectively removed cadherin complexes from junctions induced for up to 3 h, while desmosomes were not perturbed. In addition, withdrawal of cadherins from intercellular junctions temporally precedes the removal of CD44 and integrins, other microfilament-associated receptors. Our data showed that the concerted action of Rho and Rac modulate the establishment of cadherin adhesion: a constitutively active form of Rac was not sufficient to stabilize cadherindependent cell–cell contacts when endogenous Rho was inhibited. Upon induction of calcium-dependent intercellular adhesion, there was a rapid accumulation of actin at sites of cell–cell contacts, which was prevented by blocking cadherin function, Rho or Rac activity. However, if cadherin complexes are clustered by specific antibodies attached to beads, actin recruitment to the receptors was perturbed by inhibiting Rac but not Rho. Our results provide new insights into the role of the small GTPases in the cadherin-dependent cell– cell contact formation and the remodelling of actin filaments in epithelial cells.

scholarly journals Epithelial Cell Polarity Alters Rho-GTPase Responses toPseudomonas aeruginosa

2004 ◽  
Vol 15 (2) ◽  
pp. 411-419 ◽  
Author(s):  
Barbara I. Kazmierczak ◽  
Keith Mostov ◽  
Joanne N. Engel
Keyword(s):  
Epithelial Cells ◽  
Cell Polarity ◽  
Actin Polymerization ◽  
Rho Gtpase ◽  
Mdck Cells ◽  
Surface Proteins ◽  
Downstream Signaling ◽  
Rho Family Gtpases ◽  
Rho Family ◽  
Opportunistic Human Pathogen

Pseudomonas aeruginosa is an opportunistic human pathogen that preferentially infects damaged epithelial tissues. Previous studies have failed to distinguish whether the increased susceptibility of injured epithelium results from the loss of cell polarity or increased access to the basolateral surface. We have used confluent monolayers of Madin-Darby canine kidney (MDCK) cells cultured on porous filter supports for 1-3 d as a model system to investigate whether the differentiation state of a polarized model epithelium affected the response of epithelial cells to this pathogen. Confluent incompletely polarized MDCK cell monolayers (day 1) efficiently internalized apically applied P. aeruginosa via a pathway that required actin polymerization and activation of Rho-family GTPases and was accompanied by an increase in the amount of activated RhoA. In contrast, P. aeruginosa entry into highly polarized MDCK monolayers (day 3) was 10- to 100-fold less efficient and was insensitive to inhibitors of actin polymerization or of Rho-family GTPase activation. There was no activation of RhoA; instead, Cdc42-GTP levels increased significantly. Basolateral infection of highly polarized MDCK monolayers was less efficient and insensitive to Clostridium difficile Toxin B, whereas basolateral infection of incompletely polarized MDCK monolayers was more efficient and required activation of Rho-family GTPases. Together, our findings suggest that as epithelial barrier differentiates and becomes highly polarized, it becomes resistant to P. aeruginosa infection. Nevertheless, polarized epithelial cells still sense the presence of apically infecting P. aeruginosa, but they may do so through a different group of surface proteins and/or downstream signaling pathways than do incompletely polarized cells.

scholarly journals Multiple inhibitory ligands induce impaired T-cell immunologic synapse function in chronic lymphocytic leukemia that can be blocked with lenalidomide: establishing a reversible immune evasion mechanism in human cancer

Blood ◽  
2012 ◽  
Vol 120 (7) ◽  
pp. 1412-1421 ◽  
Author(s):  
Alan G. Ramsay ◽  
Andrew J. Clear ◽  
Rewas Fatah ◽  
John G. Gribben
Keyword(s):  
T Cells ◽  
T Cell ◽  
Chronic Lymphocytic Leukemia ◽  
Immune Evasion ◽  
Actin Polymerization ◽  
Rho Gtpase ◽  
Small Gtpases ◽  
Lymphocytic Leukemia ◽  
Functional Screening ◽  
Immunologic Synapse

Abstract Cancer immune evasion is an emerging hallmark of disease progression. We have demonstrated previously that impaired actin polymerization at the T-cell immunologic synapse is a global immune dysfunction in chronic lymphocytic leukemia (CLL). Direct contact with tumor cells induces defective actin polarization at the synapse in previously healthy T cells, but the molecules mediating this dysfunction were not known. In the present study, we show via functional screening assays that CD200, CD270, CD274, and CD276 are coopted by CLL cells to induce impaired actin synapse formation in both allogeneic and autologous T cells. We also show that inhibitory ligand–induced impairment of T-cell actin dynamics is a common immunosuppressive strategy used by both hematologic (including lymphoma) and solid carcinoma cells. This immunosuppressive signaling targets T-cell Rho-GTPase activation. Of clinical relevance, the immunomodulatory drug lenalidomide prevented the induction of these defects by down-regulating tumor cell–inhibitory molecule expression. These results using human CLL as a model cancer establish a novel evasion mechanism whereby malignant cells exploit multiple inhibitory ligand signaling to down-regulate small GTPases and lytic synapse function in global T-cell populations. These findings should contribute to the design of immunotherapeutic strategies to reverse T-cell tolerance in cancer.

scholarly journals Bacterial Guanine Nucleotide Exchange Factors SopE-Like and WxxxE Effectors

2010 ◽  
Vol 78 (4) ◽  
pp. 1417-1425 ◽  
Author(s):  
Richard Bulgin ◽  
Benoit Raymond ◽  
James A. Garnett ◽  
Gad Frankel ◽  
Valerie F. Crepin ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rho Gtpases ◽  
Shigella Flexneri ◽  
Small Gtpases ◽  
Effector Proteins ◽  
Actin Dynamics ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
T3ss Effector

ABSTRACT Subversion of Rho family small GTPases, which control actin dynamics, is a common infection strategy used by bacterial pathogens. In particular, Salmonella enterica serovar Typhimurium, Shigella flexneri, enteropathogenic Escherichia coli (EPEC), and enterohemorrhagic Escherichia coli (EHEC) translocate type III secretion system (T3SS) effector proteins to modulate the Rho GTPases RhoA, Cdc42, and Rac1, which trigger formation of stress fibers, filopodia, and lamellipodia/ruffles, respectively. The Salmonella effector SopE is a guanine nucleotide exchange factor (GEF) that activates Rac1 and Cdc42, which induce “the trigger mechanism of cell entry.” Based on a conserved Trp-xxx-Glu motif, the T3SS effector proteins IpgB1 and IpgB2 of Shigella, SifA and SifB of Salmonella, and Map of EPEC and EHEC were grouped together into a WxxxE family; recent studies identified the T3SS EPEC and EHEC effectors EspM and EspT as new family members. Recent structural and functional studies have shown that representatives of the WxxxE effectors share with SopE a 3-D fold and GEF activity. In this minireview, we summarize contemporary findings related to the SopE and WxxxE GEFs in the context of their role in subverting general host cell signaling pathways and infection.

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 Regulation of Rho GTPases in the Vasculature by Cullin3-Based E3 Ligase Complexes

2021 ◽  
Vol 9 ◽  
Author(s):  
Fabienne Podieh ◽  
Peter L. Hordijk
Keyword(s):  
Rho Gtpases ◽  
Vascular Function ◽  
Rho Gtpase ◽  
Current Knowledge ◽  
E3 Ligase ◽  
Small Gtpases ◽  
E3 Ligases ◽  
Cellular Processes ◽  
Ubiquitin E3 Ligase ◽  
Cytoskeletal Dynamics

Cullin3-based ubiquitin E3 ligases induce ubiquitination of substrates leading to their proteasomal or lysosomal degradation. BTB proteins serve as adaptors by binding to Cullin3 and recruiting substrate proteins, which enables specific recognition of a broad spectrum of targets. Hence, Cullin3 and its adaptors are involved in myriad cellular processes and organ functions. Cullin3-based ubiquitin E3 ligase complexes target small GTPases of the Rho subfamily, which are key regulators of cytoskeletal dynamics and cell adhesion. In this mini review, we discuss recent insights in Cullin3-mediated regulation of Rho GTPases and their impact on cellular function and disease. Intriguingly, upstream regulators of Rho GTPases are targeted by Cullin3 complexes as well. Thus, Rho GTPase signaling is regulated by Cullin3 on multiple levels. In addition, we address current knowledge of Cullin3 in regulating vascular function, focusing on its prominent role in endothelial barrier function, angiogenesis and the regulation of blood pressure.

scholarly journals Multiple Sequence Elements Facilitate Chp Rho GTPase Subcellular Location, Membrane Association, and Transforming Activity

2006 ◽  
Vol 17 (7) ◽  
pp. 3108-3121 ◽  
Author(s):  
Emily J. Chenette ◽  
Natalia Y. Mitin ◽  
Channing J. Der
Keyword(s):  
Amino Acids ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Subcellular Location ◽  
Small Gtpases ◽  
Membrane Association ◽  
Basic Amino Acids ◽  
Sequence Elements ◽  
Transforming Activity ◽  
Carboxy Terminal

Cdc42 homologous protein (Chp) is a member of the Rho family of small GTPases and shares significant sequence and functional similarity with Cdc42. However, unlike classical Rho GTPases, we recently found that Chp depends on palmitoylation, rather than prenylation, for association with cellular membranes. Because palmitoylation alone is typically not sufficient to promote membrane association, we evaluated the possibility that other carboxy-terminal residues facilitate Chp subcellular association with membranes. We found that Chp membrane association and transforming activity was dependent on the integrity of a stretch of basic amino acids in the carboxy terminus of Chp and that the basic amino acids were not simply part of a palmitoyl acyltransferase recognition motif. We also determined that the 11 carboxy-terminal residues alone were sufficient to promote Chp plasma and endomembrane association. Interestingly, stimulation with tumor necrosis factor-α activated only endomembrane-associated Chp. Finally, we found that Chp membrane association was not disrupted by Rho guanine nucleotide dissociation inhibitory proteins, which are negative regulators of Cdc42 membrane association and biological activity. In summary, the unique carboxy-terminal sequence elements that promote Chp subcellular location and function expand the complexity of mechanisms by which the cellular functions of Rho GTPases are regulated.

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