1
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Kowluru A, Gleason NF. Underappreciated roles for Rho GDP dissociation inhibitors (RhoGDIs) in cell function: Lessons learned from the pancreatic islet β-cell. Biochem Pharmacol 2022; 197:114886. [PMID: 34968495 PMCID: PMC8858860 DOI: 10.1016/j.bcp.2021.114886] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/10/2021] [Accepted: 12/13/2021] [Indexed: 11/02/2022]
Abstract
Rho subfamily of G proteins (e.g., Rac1) have been implicated in glucose-stimulated insulin secretion from the pancreatic β-cell. Interestingly, metabolic stress (e.g., chronic exposure to high glucose) results in sustained activation of Rac1 leading to increased oxidative stress, impaired insulin secretion and β-cell dysfunction. Activation-deactivation of Rho G proteins is mediated by three classes of regulatory proteins, namely the guanine nucleotide exchange factors (GEFs), which facilitate the conversion of inactive G proteins to their active conformations; the GTPase-activating proteins (GAPs), which convert the active G proteins to their inactive forms); and the GDP-dissociation inhibitors (GDIs), which prevent the dissociation of GDP from G proteins. Contrary to a large number of GEFs (82 members) and GAPs (69 members), only three members of RhoGDIs (RhoGDIα, RhoGDIβ and RhoGDIγ) are expressed in mammalian cells.Even though relatively smaller in number, the GDIs appear to play essential roles in G protein function (e.g., subcellular targeting) for effector activation and cell regulation. Emerging evidence also suggests that the GDIs are functionally regulated via post-translational modification (e.g., phosphorylation) and by lipid second messengers, lipid kinases and lipid phosphatases. We highlight the underappreciated regulatory roles of RhoGDI-Rho G protein signalome in islet β-cell function in health and metabolic stress. Potential knowledge gaps in the field, and directions for future research for the identification of novel therapeutic targets to loss of functional β-cell mass under the duress of metabolic stress are highlighted.
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Affiliation(s)
- Anjaneyulu Kowluru
- Biomedical Research Service, John D. Dingell VA Medical Center and Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
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2
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Electrostatic Forces Mediate the Specificity of RHO GTPase-GDI Interactions. Int J Mol Sci 2021; 22:ijms222212493. [PMID: 34830380 PMCID: PMC8622166 DOI: 10.3390/ijms222212493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 01/13/2023] Open
Abstract
Three decades of research have documented the spatiotemporal dynamics of RHO family GTPase membrane extraction regulated by guanine nucleotide dissociation inhibitors (GDIs), but the interplay of the kinetic mechanism and structural specificity of these interactions is as yet unresolved. To address this, we reconstituted the GDI-controlled spatial segregation of geranylgeranylated RHO protein RAC1 in vitro. Various biochemical and biophysical measurements provided unprecedented mechanistic details for GDI function with respect to RHO protein dynamics. We determined that membrane extraction of RHO GTPases by GDI occurs via a 3-step mechanism: (1) GDI non-specifically associates with the switch regions of the RHO GTPases; (2) an electrostatic switch determines the interaction specificity between the C-terminal polybasic region of RHO GTPases and two distinct negatively-charged clusters of GDI1; (3) a non-specific displacement of geranylgeranyl moiety from the membrane sequesters it into a hydrophobic cleft, effectively shielding it from the aqueous milieu. This study substantially extends the model for the mechanism of GDI-regulated RHO GTPase extraction from the membrane, and could have implications for clinical studies and drug development.
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3
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Ramirez SA, Pablo M, Burk S, Lew DJ, Elston TC. A novel stochastic simulation approach enables exploration of mechanisms for regulating polarity site movement. PLoS Comput Biol 2021; 17:e1008525. [PMID: 34264926 PMCID: PMC8315557 DOI: 10.1371/journal.pcbi.1008525] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 07/27/2021] [Accepted: 06/24/2021] [Indexed: 12/23/2022] Open
Abstract
Cells polarize their movement or growth toward external directional cues in many different contexts. For example, budding yeast cells grow toward potential mating partners in response to pheromone gradients. Directed growth is controlled by polarity factors that assemble into clusters at the cell membrane. The clusters assemble, disassemble, and move between different regions of the membrane before eventually forming a stable polarity site directed toward the pheromone source. Pathways that regulate clustering have been identified but the molecular mechanisms that regulate cluster mobility are not well understood. To gain insight into the contribution of chemical noise to cluster behavior we simulated clustering using the reaction-diffusion master equation (RDME) framework to account for molecular-level fluctuations. RDME simulations are a computationally efficient approximation, but their results can diverge from the underlying microscopic dynamics. We implemented novel concentration-dependent rate constants that improved the accuracy of RDME-based simulations, allowing us to efficiently investigate how cluster dynamics might be regulated. Molecular noise was effective in relocating clusters when the clusters contained low numbers of limiting polarity factors, and when Cdc42, the central polarity regulator, exhibited short dwell times at the polarity site. Cluster stabilization occurred when abundances or binding rates were altered to either lengthen dwell times or increase the number of polarity molecules in the cluster. We validated key results using full 3D particle-based simulations. Understanding the mechanisms cells use to regulate the dynamics of polarity clusters should provide insights into how cells dynamically track external directional cues. Cells localize polarity molecules in a small region of the plasma membrane forming a polarity cluster that directs functions such as migration, reproduction, and growth. Guided by external signals, these clusters move across the membrane allowing cells to reorient growth or motion. The polarity molecules continuously and randomly shuttle between the cluster and the cell cytosol and, as a result, the number and distribution of molecules at the cluster constantly changes. Here we present an improved stochastic simulation algorithm to investigate how such molecular-scale fluctuations induce cluster movement across the cell membrane. Unexpectedly, cluster mobility does not correlate with variations in total molecule abundance within the cluster, but rather with changes in the spatial distribution of molecules that form the cluster. Cluster motion is faster when polarity molecules are scarce and when they shuttle rapidly between the cluster and the cytosol. Our results suggest that cells control cluster mobility by regulating the abundance of polarity molecules and biochemical reactions that affect the time molecules spend at the cluster. We provide insights into how cells harness random molecular behavior to perform functions important for survival, such as detecting the direction of external signals.
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Affiliation(s)
- Samuel A. Ramirez
- Department of Pharmacology and Computational Medicine Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (SAR); (TCE)
| | - Michael Pablo
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Program in Molecular and Cellular Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Sean Burk
- Department of Pharmacology and Computational Medicine Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Daniel J. Lew
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, United States of America
| | - Timothy C. Elston
- Department of Pharmacology and Computational Medicine Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (SAR); (TCE)
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4
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Sadri S, Tomar N, Yang C, Audi SH, Cowley AW, Dash RK. Mechanistic computational modeling of the kinetics and regulation of NADPH oxidase 2 assembly and activation facilitating superoxide production. Free Radic Res 2020; 54:695-721. [PMID: 33059489 DOI: 10.1080/10715762.2020.1836368] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Reactive oxygen species (ROS) play a crucial role in many physiological processes. However, ROS overproduction leads to oxidative stress, which plays a critical role in cell injury/death and the pathogenesis of many diseases. Members of NADPH oxidase (NOX) family, most of which are comprised of membrane and cytosolic components, are known to be the major nonmitochondrial sources of ROS in many cells. NOX2 is a widely-expressed and well-studied NOX family member, which is activated upon assembly of its membrane subunits gp91 phox and p22 phox with its cytosolic subunits p40 phox , p47 phox , p67 phox , and Rac, facilitating ROS production. NOX2 activation is also enhanced by GTP and inhibited by GDP. However, there remains a lack of a mechanistic, quantitative, and integrated understanding of the kinetics and regulation of the assembly of these subunits and their relative contributions toward NOX2 activation and ROS production. Toward this end, we have developed a mechanistic computational model, which incorporates a generalized random rapid equilibrium binding mechanism for NOX2 assembly and activation as well as regulations by GTP (activation), GDP (inhibition), and individual subunits enhancing the binding of other subunits (mutual binding enhancement). The resulting model replicates diverse published kinetic data, including subunit concentration-dependent NOX2 activation and ROS production, under different assay conditions, with appropriate estimates of the unknown model parameters. The model provides a mechanistic, quantitative, and integrated framework for investigating the critical roles of NOX2 subunits in NOX2 assembly and activation facilitating ROS production in a variety of physiological and pathophysiological conditions. However, there is also a need for better quantitative kinetic data based on current understanding of NOX2 assembly and activation in order to test and further develop this model.
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Affiliation(s)
- Shima Sadri
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, WIS, USA
| | - Namrata Tomar
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, WIS, USA
| | - Chun Yang
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WIS, USA
| | - Said H Audi
- Department of Biomedical Engineering, Marquette University, Milwaukee, WIS, USA
| | - Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WIS, USA
| | - Ranjan K Dash
- Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, WIS, USA.,Department of Physiology, Medical College of Wisconsin, Milwaukee, WIS, USA
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Abstract
The superoxide (O2·-)-generating NADPH oxidase complex of phagocytes comprises a membrane-associated heterodimeric flavocytochrome, known as cytochrome b 558 (consisting of NOX2 and p22phox) and four cytosolic regulatory proteins, p47phox, p67phox, p40phox, and the small GTPase Rac. Under physiological conditions, in the resting phagocyte, O2·- generation is initiated by engagement of membrane receptors by a variety of stimuli, followed by signal transduction sequences leading to the translocation of the cytosolic components to the membrane and their association with the cytochrome, a process known as NADPH oxidase assembly. A consequent conformational change in NOX2 initiates the electron flow along a redox gradient, from NADPH to molecular oxygen (O2), leading to the one-electron reduction of O2 to O2·-. Historically, methodological difficulties in the study of the assembled complex derived from stimulated cells, due to its lack of stability, led to the design of "cell-free" systems (also known as "broken cells" or in vitro systems). In a major paradigm shift, the cell-free systems have as their starting point NADPH oxidase components derived from resting (unstimulated) phagocytes, or as in the predominant method at present, recombinant proteins representing the components of the NADPH oxidase complex. In cell-free systems, membrane receptor stimulation and the signal transduction sequence are absent, the accent being placed on the actual process of assembly, all of which takes place in vitro. Thus, a mixture of the individual components of the NADPH oxidase is exposed in vitro to an activating agent, the most common being anionic amphiphiles, resulting in the formation of a complex between cytochrome b 558 and the cytosolic components and O2·- generation in the presence of NADPH. Alternative activating pathways require posttranslational modification of oxidase components or modifying the phospholipid milieu surrounding cytochrome b 558. Activation is commonly quantified by measuring the primary product of the reaction, O2·-, trapped immediately after its generation by an appropriate acceptor in a kinetic assay, permitting the calculation of rates of O2·- production, but numerous variations exist, based on the assessment of reaction products or the consumption of substrates. Cell-free assays played a paramount role in the identification and characterization of the components of the NADPH oxidase complex, the performance of structure-function studies, the deciphering of the mechanisms of assembly, the search for inhibitory drugs, and the diagnosis of various forms of chronic granulomatous disease (CGD).
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Mohammad G, Duraisamy AJ, Kowluru A, Kowluru RA. Functional Regulation of an Oxidative Stress Mediator, Rac1, in Diabetic Retinopathy. Mol Neurobiol 2019; 56:8643-8655. [PMID: 31300985 PMCID: PMC6842106 DOI: 10.1007/s12035-019-01696-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 07/03/2019] [Indexed: 12/31/2022]
Abstract
PURPOSE Early activation of cytosolic NADPH oxidase-2 (Nox2) in diabetes increases retinal ROS production, damaging their mitochondria. The assembly of Nox2 holoenzyme requires activation of a small molecular weight G protein Rac1. Rac1 activation is regulated by guanine exchange factors and guanine nucleotide-dissociation inhibitors, and post-translational modifications assist in its association with exchange factors and dissociation inhibitors. The goal of this study is to investigate the mechanisms of Rac1 activation in the development of diabetic retinopathy. METHODS The levels of the dissociation inhibitor, prenylating enzyme (farnesyltransferase, FNTA), and exchange factor Vav2 were quantified in human retinal endothelial cells, incubated in normal or high glucose for 96 h. The roles of prenylation and Vav2 in Rac1-Nox2-ROS mitochondrial damage were confirmed in FNTA-siRNA-transfected cells and using the Vav2 inhibitor EHop, respectively. Retinal histopathology and functional changes associated with diabetic retinopathy were analyzed in diabetic mice receiving EHop for 6 months. Key parameters of Rac1 activation were confirmed in the retinal microvasculature from human donors with diabetic retinopathy. RESULTS In HRECs, glucose increased FNTA and Vav2 and decreased the dissociation inhibitor. FNTA-siRNA and EHop inhibited glucose-induced activation of Rac1-Nox2-ROS signaling. In diabetic mice, EHop ameliorated the development of retinopathy and functional/structural abnormalities and attenuated Rac1-Nox2-mitochondrial damage. Similar alterations in Rac1 regulators were observed in retinal microvasculature from human donors with diabetic retinopathy. In diabetes, Rac1 prenylation and its interactions with Vav2 contribute to Nox2-ROS-mitochondrial damage, and the pharmacological inhibitors to attenuate Rac1 interactions with its regulators could have the potential to halt/inhibit the development of diabetic retinopathy. Graphical Abstract Activation of prenylating enzyme farnesyltransferase (FNTA) in diabetes, prenylates Rac1. The binding of Rac1 with guanine nucleotide-dissociation inhibitor (GDI) is decreased, but its association with the guanine exchange factor, Vav2, is increased, resulting in Rac1 activation. Active Rac1 helps in the assembly of Nox2 holoenzyme, and Nox2 activation increases cytosolic ROS production, damaging the mitochondria. Damaged mitochondria accelerate capillary cell apoptosis, and ultimately, results in the development of diabetic retinopathy.
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Affiliation(s)
- Ghulam Mohammad
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, 4717 St. Antoine, Detroit, MI, 48201, USA
| | - Arul J Duraisamy
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, 4717 St. Antoine, Detroit, MI, 48201, USA
| | - Anjan Kowluru
- Pharmaceutical Sciences, Wayne State University, Detroit, MI, USA
- John D. Dingell VA Medical Center, Detroit, MI, USA
| | - Renu A Kowluru
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University, 4717 St. Antoine, Detroit, MI, 48201, USA.
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7
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Ueyama T. Rho-Family Small GTPases: From Highly Polarized Sensory Neurons to Cancer Cells. Cells 2019; 8:cells8020092. [PMID: 30696065 PMCID: PMC6406560 DOI: 10.3390/cells8020092] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 01/19/2019] [Accepted: 01/23/2019] [Indexed: 12/22/2022] Open
Abstract
The small GTPases of the Rho-family (Rho-family GTPases) have various physiological functions, including cytoskeletal regulation, cell polarity establishment, cell proliferation and motility, transcription, reactive oxygen species (ROS) production, and tumorigenesis. A relatively large number of downstream targets of Rho-family GTPases have been reported for in vitro studies. However, only a small number of signal pathways have been established at the in vivo level. Cumulative evidence for the functions of Rho-family GTPases has been reported for in vivo studies using genetically engineered mouse models. It was based on different cell- and tissue-specific conditional genes targeting mice. In this review, we introduce recent advances in in vivo studies, including human patient trials on Rho-family GTPases, focusing on highly polarized sensory organs, such as the cochlea, which is the primary hearing organ, host defenses involving reactive oxygen species (ROS) production, and tumorigenesis (especially associated with RAC, novel RAC1-GSPT1 signaling, RHOA, and RHOBTB2).
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Affiliation(s)
- Takehiko Ueyama
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan.
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8
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Rac1 Nanoscale Organization on the Plasma Membrane Is Driven by Lipid Binding Specificity Encoded in the Membrane Anchor. Mol Cell Biol 2018; 38:MCB.00186-18. [PMID: 29967243 DOI: 10.1128/mcb.00186-18] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 06/21/2018] [Indexed: 12/21/2022] Open
Abstract
Rac1 is a small guanine nucleotide binding protein that cycles between an inactive GDP-bound and active GTP-bound state to regulate cell motility and migration. Rac1 signaling is initiated from the plasma membrane (PM). Here, we used high-resolution spatial mapping and manipulation of PM lipid composition to define Rac1 nanoscale organization. We found that Rac1 proteins in the GTP- and GDP-bound states assemble into nonoverlapping nanoclusters; thus, Rac1 proteins undergo nucleotide-dependent segregation. Rac1 also selectively interacts with phosphatidic acid (PA) and phosphoinositol (3,4,5)-trisphosphate (PIP3), resulting in nanoclusters enriched in these lipids. These lipids are structurally important because depleting the PM of PA or PIP3 impairs both Rac1 PM binding and Rac1 nanoclustering. Lipid binding specificity of Rac1 is encoded in the amino acid sequence of the polybasic domain (PBD) of the C-terminal membrane anchor. Point mutations within the PBD, including arginine-to-lysine substitutions, profoundly alter Rac1 lipid binding specificity without changing the electrostatics of the protein and result in impaired macropinocytosis and decreased cell spreading. We propose that Rac1 nanoclusters act as lipid-based signaling platforms emulating the spatiotemporal organization of Ras proteins and show that the Rac1 PBD-prenyl anchor has a biological function that extends beyond simple electrostatic engagement with the PM.
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9
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Clustering of Rac1: Selective Lipid Sorting Drives Signaling. Trends Biochem Sci 2018; 43:75-77. [DOI: 10.1016/j.tibs.2017.11.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 11/21/2017] [Indexed: 11/17/2022]
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10
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Moretti AIS, Pavanelli JC, Nolasco P, Leisegang MS, Tanaka LY, Fernandes CG, Wosniak J, Kajihara D, Dias MH, Fernandes DC, Jo H, Tran NV, Ebersberger I, Brandes RP, Bonatto D, Laurindo FRM. Conserved Gene Microsynteny Unveils Functional Interaction Between Protein Disulfide Isomerase and Rho Guanine-Dissociation Inhibitor Families. Sci Rep 2017; 7:17262. [PMID: 29222525 PMCID: PMC5722932 DOI: 10.1038/s41598-017-16947-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 11/21/2017] [Indexed: 02/07/2023] Open
Abstract
Protein disulfide isomerases (PDIs) support endoplasmic reticulum redox protein folding and cell-surface thiol-redox control of thrombosis and vascular remodeling. The family prototype PDIA1 regulates NADPH oxidase signaling and cytoskeleton organization, however the related underlying mechanisms are unclear. Here we show that genes encoding human PDIA1 and its two paralogs PDIA8 and PDIA2 are each flanked by genes encoding Rho guanine-dissociation inhibitors (GDI), known regulators of RhoGTPases/cytoskeleton. Evolutionary histories of these three microsyntenic regions reveal their emergence by two successive duplication events of a primordial gene pair in the last common vertebrate ancestor. The arrangement, however, is substantially older, detectable in echinoderms, nematodes, and cnidarians. Thus, PDI/RhoGDI pairing in the same transcription orientation emerged early in animal evolution and has been largely maintained. PDI/RhoGDI pairs are embedded into conserved genomic regions displaying common cis-regulatory elements. Analysis of gene expression datasets supports evidence for PDI/RhoGDI coexpression in developmental/inflammatory contexts. PDIA1/RhoGDIα were co-induced in endothelial cells upon CRISP-R-promoted transcription activation of each pair component, and also in mouse arterial intima during flow-induced remodeling. We provide evidence for physical interaction between both proteins. These data support strong functional links between PDI and RhoGDI families, which likely maintained PDI/RhoGDI microsynteny along > 800-million years of evolution.
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Affiliation(s)
- Ana I S Moretti
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - Jessyca C Pavanelli
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - Patrícia Nolasco
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | | | - Leonardo Y Tanaka
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - Carolina G Fernandes
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - João Wosniak
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - Daniela Kajihara
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - Matheus H Dias
- Special Laboratory for Cell Cycle, Center of Toxins, Immune-Response and Cell Signaling - CeTICS-Cepid, Butantan Institute, São Paulo, Brazil
| | - Denise C Fernandes
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil
| | - Hanjoong Jo
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, USA
| | - Ngoc-Vinh Tran
- Applied Bioinformatics Group, Institute of Cell Biology & Neuroscience, Goethe University, Frankfurt, Germany
| | - Ingo Ebersberger
- Applied Bioinformatics Group, Institute of Cell Biology & Neuroscience, Goethe University, Frankfurt, Germany
- Senckenberg Biodiversity and Climate Research Center (BiK-F), Frankfurt, Germany
| | - Ralf P Brandes
- Institut für Kardiovaskuläre Physiologie, Goethe University, Frankfurt, Germany
| | - Diego Bonatto
- Department of Molecular Biology and Biotechnology, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - Francisco R M Laurindo
- Vascular Biology Laboratory, Heart Institute (Incor), University of São Paulo School of Medicine, São Paulo, Brazil.
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11
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Goryachev AB, Leda M. Many roads to symmetry breaking: molecular mechanisms and theoretical models of yeast cell polarity. Mol Biol Cell 2017; 28:370-380. [PMID: 28137950 PMCID: PMC5341721 DOI: 10.1091/mbc.e16-10-0739] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 11/17/2016] [Accepted: 11/23/2016] [Indexed: 01/08/2023] Open
Abstract
Mathematical modeling has been instrumental in identifying common principles of cell polarity across diverse systems. These principles include positive feedback loops that are required to destabilize a spatially uniform state of the cell. The conserved small G-protein Cdc42 is a master regulator of eukaryotic cellular polarization. Here we discuss recent developments in studies of Cdc42 polarization in budding and fission yeasts and demonstrate that models describing symmetry-breaking polarization can be classified into six minimal classes based on the structure of positive feedback loops that activate and localize Cdc42. Owing to their generic system-independent nature, these model classes are also likely to be relevant for the G-protein–based symmetry-breaking systems of higher eukaryotes. We review experimental evidence pro et contra different theoretically plausible models and conclude that several parallel and non–mutually exclusive mechanisms are likely involved in cellular polarization of yeasts. This potential redundancy needs to be taken into consideration when interpreting the results of recent cell-rewiring studies.
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Affiliation(s)
- Andrew B Goryachev
- Center for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
| | - Marcin Leda
- Center for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, United Kingdom
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12
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Hodgson L, Spiering D, Sabouri-Ghomi M, Dagliyan O, DerMardirossian C, Danuser G, Hahn KM. FRET binding antenna reports spatiotemporal dynamics of GDI-Cdc42 GTPase interactions. Nat Chem Biol 2016; 12:802-809. [PMID: 27501396 PMCID: PMC5030135 DOI: 10.1038/nchembio.2145] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 05/16/2016] [Indexed: 12/29/2022]
Abstract
Guanine-nucleotide dissociation inhibitors (GDIs) are negative regulators of Rho family GTPases that sequester the GTPases away from the membrane. Here we ask how GDI-Cdc42 interaction regulates localized Cdc42 activation for cell motility. The sensitivity of cells to overexpression of Rho family pathway components led us to a new biosensor, GDI.Cdc42 FLARE, in which Cdc42 is modified with a fluorescence resonance energy transfer (FRET) 'binding antenna' that selectively reports Cdc42 binding to endogenous GDIs. Similar antennae could also report GDI-Rac1 and GDI-RhoA interaction. Through computational multiplexing and simultaneous imaging, we determined the spatiotemporal dynamics of GDI-Cdc42 interaction and Cdc42 activation during cell protrusion and retraction. This revealed remarkably tight coordination of GTPase release and activation on a time scale of 10 s, suggesting that GDI-Cdc42 interactions are a critical component of the spatiotemporal regulation of Cdc42 activity, and not merely a mechanism for global sequestration of an inactivated pool of signaling molecules.
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Affiliation(s)
- Louis Hodgson
- Department of Anatomy and Structural Biology and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine.,Department of Pharmacology and Lineberger Cancer Center, University of North Carolina at Chapel Hill
| | - Désirée Spiering
- Department of Anatomy and Structural Biology and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine
| | | | - Onur Dagliyan
- Department of Pharmacology and Lineberger Cancer Center, University of North Carolina at Chapel Hill
| | | | - Gaudenz Danuser
- Department of Cell Biology, The Scripps Research Institute.,Department of Cell Biology, Harvard Medical School
| | - Klaus M Hahn
- Department of Pharmacology and Lineberger Cancer Center, University of North Carolina at Chapel Hill
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13
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Wang C, Pan Z, Hou H, Li D, Mo Y, Mo C, Li J. The Enhancement of Radiation Sensitivity in Nasopharyngeal Carcinoma Cells via Activation of the Rac1/NADPH Signaling Pathway. Radiat Res 2016; 185:638-46. [PMID: 27243897 DOI: 10.1667/rr14331.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We reported in an earlier study that using mass spectrometry and bioinformatic analysis demonstrated Rac1 protein might be mostly mitochondrial target in the radiosensitization process of nasopharyngeal carcinoma CNE-1 cells. The goal of our current study was to reveal the relationship between Rac1/NADPH pathway and radiosensitization in CNE-1 cells using Rac1 activator, phorbol 12-myristate 13-acetate (PMA) and Rac1 inhibitor NSC23766. The Rac1-GTP expression was determined using a pulldown assay, the Rac1 location using a immunofluorescence with a laser scanning confocal microscope, the NADPH oxidase activity with NBT assay and the reactive oxygen species with DCFH-DA probe. The apoptosis rate was analyzed by flow cytometry, and the expressions of p67(phox) and NFκB-p105/p50 were analyzed by Western blot. After treatment with PMA and 2 Gy radiation (compared to the control), Rac1-GTP was activated and translocated to the cell membrane. NADPH oxidase activity, reactive oxygen species of intracellular concentration and the apoptosis rate increased significantly. The expression of p67(phox) and NFκB-p50 protein also increased. However, in the cells treated with NSC23766 alone or NSC23766 combined with 2 Gy irradiation, the results were just the opposite. Overall, these results indicate that the Rac1 protein may be the key target involved in the radiosensitization of nasopharyngeal carcinoma cells. The activated Rac1/NADPH pathway combined with radiation can increase the radiosensitivity of nasopharyngeal carcinoma cells, and the Rac1/NADPH pathway may be the signaling pathway involved in the radiosensitization process.
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Affiliation(s)
- Chunmiao Wang
- a College of Pharmacy, Guangxi Medical University, Nanning 530021, China; and
| | - Zhiyu Pan
- a College of Pharmacy, Guangxi Medical University, Nanning 530021, China; and
| | - Huaxin Hou
- a College of Pharmacy, Guangxi Medical University, Nanning 530021, China; and
| | - Danrong Li
- b Department of Basic Research, Guangxi Institute for Cancer Research, Nanning, 530021, China
| | - Yuanyuan Mo
- a College of Pharmacy, Guangxi Medical University, Nanning 530021, China; and
| | - Chunyan Mo
- a College of Pharmacy, Guangxi Medical University, Nanning 530021, China; and
| | - Jing Li
- a College of Pharmacy, Guangxi Medical University, Nanning 530021, China; and
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14
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Chavan TS, Jang H, Khavrutskii L, Abraham SJ, Banerjee A, Freed BC, Johannessen L, Tarasov SG, Gaponenko V, Nussinov R, Tarasova NI. High-Affinity Interaction of the K-Ras4B Hypervariable Region with the Ras Active Site. Biophys J 2015; 109:2602-2613. [PMID: 26682817 PMCID: PMC4699860 DOI: 10.1016/j.bpj.2015.09.034] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 09/08/2015] [Accepted: 09/16/2015] [Indexed: 12/24/2022] Open
Abstract
Ras proteins are small GTPases that act as signal transducers between cell surface receptors and several intracellular signaling cascades. They contain highly homologous catalytic domains and flexible C-terminal hypervariable regions (HVRs) that differ across Ras isoforms. KRAS is among the most frequently mutated oncogenes in human tumors. Surprisingly, we found that the C-terminal HVR of K-Ras4B, thought to minimally impact the catalytic domain, directly interacts with the active site of the protein. The interaction is almost 100-fold tighter with the GDP-bound than the GTP-bound protein. HVR binding interferes with Ras-Raf interaction, modulates binding to phospholipids, and slightly slows down nucleotide exchange. The data indicate that contrary to previously suggested models of K-Ras4B signaling, HVR plays essential roles in regulation of signaling. High affinity binding of short peptide analogs of HVR to K-Ras active site suggests that targeting this surface with inhibitory synthetic molecules for the therapy of KRAS-dependent tumors is feasible.
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Affiliation(s)
- Tanmay S Chavan
- Medicinal Chemistry Department, University of Illinois at Chicago, Chicago, Illinois; Biochemistry and Molecular Genetics Department, University of Illinois at Chicago, Chicago, Illinois
| | - Hyunbum Jang
- Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland; Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, Maryland
| | - Lyuba Khavrutskii
- Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland; Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, Maryland
| | - Sherwin J Abraham
- Biochemistry and Molecular Genetics Department, University of Illinois at Chicago, Chicago, Illinois
| | - Avik Banerjee
- Chemistry Department, University of Illinois at Chicago, Chicago, Illinois; Structural Biophysics Laboratory, National Cancer Institute at Frederick, Frederick, Maryland
| | - Benjamin C Freed
- Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, Maryland
| | - Liv Johannessen
- Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, Maryland
| | - Sergey G Tarasov
- Chemistry Department, University of Illinois at Chicago, Chicago, Illinois; Structural Biophysics Laboratory, National Cancer Institute at Frederick, Frederick, Maryland
| | - Vadim Gaponenko
- Biochemistry and Molecular Genetics Department, University of Illinois at Chicago, Chicago, Illinois.
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland; Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, Maryland; Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
| | - Nadya I Tarasova
- Cancer and Inflammation Program, National Cancer Institute at Frederick, Frederick, Maryland.
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15
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Abstract
Phagocytosis is defined as a cellular uptake pathway for particles of greater than 0.5 μm in diameter. Particle clearance by phagocytosis is of critical importance for tissue health and homeostasis. The ultimate goal of anti-pathogen phagocytosis is to destroy engulfed bacteria or fungi and to stimulate cell-cell signaling that mount an efficient immune defense. In contrast, clearance phagocytosis of apoptotic cells and cell debris is anti-inflammatory. High capacity clearance phagocytosis pathways are available to professional phagocytes of the immune system and the retina. Additionally, a low capacity, so-called bystander phagocytic pathway is available to most other cell types. Different phagocytic pathways are stimulated by particle ligation of distinct surface receptors but all forms of phagocytosis require F-actin recruitment beneath tethered particles and F-actin re-arrangement promoting engulfment, which are controlled by Rho family GTPases. The specificity of Rho GTPase activity during the different forms of phagocytosis by mammalian cells is the subject of this review.
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Affiliation(s)
- Yingyu Mao
- a Department of Biological Sciences; Center for Cancer, Genetic Diseases, and Gene Regulation; Fordham University ; Bronx , NY , USA
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16
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Single-molecule tracking of small GTPase Rac1 uncovers spatial regulation of membrane translocation and mechanism for polarized signaling. Proc Natl Acad Sci U S A 2015; 112:E267-76. [PMID: 25561548 DOI: 10.1073/pnas.1409667112] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polarized Rac1 signaling is a hallmark of many cellular functions, including cell adhesion, motility, and cell division. The two steps of Rac1 activation are its translocation to the plasma membrane and the exchange of nucleotide from GDP to GTP. It is, however, unclear whether these two processes are regulated independent of each other and what their respective roles are in polarization of Rac1 signaling. We designed a single-particle tracking (SPT) method to quantitatively analyze the kinetics of Rac1 membrane translocation in living cells. We found that the rate of Rac1 translocation was significantly elevated in protrusions during cell spreading on collagen. Furthermore, combining FRET sensor imaging with SPT measurements in the same cell, the recruitment of Rac1 was found to be polarized to an extent similar to that of the nucleotide exchange process. Statistical analysis of single-molecule trajectories and optogenetic manipulation of membrane lipids revealed that Rac1 membrane translocation precedes nucleotide exchange, and is governed primarily by interactions with phospholipids, particularly PI(3,4,5)P3, instead of protein factors. Overall, the study highlights the significance of membrane translocation in spatial Rac1 signaling, which is in addition to the traditional view focusing primarily on GEF distribution and exchange reaction.
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17
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Morin A, Cordelières FP, Cherfils J, Olofsson B. RhoGDI3 and RhoG: Vesicular trafficking and interactions with the Sec3 Exocyst subunit. Small GTPases 2014; 1:142-156. [PMID: 21686268 DOI: 10.4161/sgtp.1.3.15112] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 02/04/2011] [Accepted: 02/07/2011] [Indexed: 12/13/2022] Open
Abstract
RhoGDIs are negative regulators of small GTP-binding proteins of the Rho family, which have essential cellular functions in most aspects of actin-based morphology and motility processes. They extract Rho proteins from membranes, keep them in inactive rhoGDI/Rho complexes and eventually deliver them again to specific membranes in response to cellular signals. RhoGDI3, the most divergent member of the rhoGDI family, is well suited to document the underlying molecular mechanisms, since the active and inactive forms of its cellular target, RhoG, have well-separated subcellular localizations. In this study, we investigate trafficking structures and molecular interactions involved in rhoGDI3-mediated shuttling of RhoG between the Golgi and the plasma membrane.Bimolecular fluorescence complementation and acceptor-photobleaching FRET experiments suggest that rhoGDI3 and RhoG form complexes on Golgi and vesicular structures in mammalian cells. 4D-videomicroscopy confirms this localization, and show that RhoG/rhoGDI3-labelled structures are less dynamic than RhoG and rhoGDI3-labeled vesicles, consistent with the inhibitory function of rhoGDI3. Next, we identify the Exocyst subunit Sec3 as a candidate rhoGDI3 partner in cells. RhoGDI3 relocates a subcomplex of the Exocyst (Sec3 and Sec8) from the cytoplasm to the Golgi, while Sec6 is unaffected. Remarkably, Sec3 increases the level of GTP-bound endogenous RhoG, the RhoG-dependent induction of membrane ruffles, and the formation of intercellular tunneling nanotube-like protrusions.Altogether, our study identifies a novel link between vesicular traffic and the regulation of Rho proteins by rhoGDIs. It also suggests that components of the Exocyst machinery may be involved in RhoG functions, possibly regulated by rhoGDI3.
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Affiliation(s)
- Annie Morin
- Laboratoire d'Enzymologie et Biochimie Structurales; Centre de Recherche de Gif-sur-Yvette; CNRS; Gif-sur-Yvette, France
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18
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Zhang SC, Gremer L, Heise H, Janning P, Shymanets A, Cirstea IC, Krause E, Nürnberg B, Ahmadian MR. Liposome reconstitution and modulation of recombinant prenylated human Rac1 by GEFs, GDI1 and Pak1. PLoS One 2014; 9:e102425. [PMID: 25014207 PMCID: PMC4094549 DOI: 10.1371/journal.pone.0102425] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 06/18/2014] [Indexed: 11/19/2022] Open
Abstract
Small Rho GTPases are well known to regulate a variety of cellular processes by acting as molecular switches. The regulatory function of Rho GTPases is critically dependent on their posttranslational modification at the carboxyl terminus by isoprenylation and association with proper cellular membranes. Despite numerous studies, the mechanisms of recycling and functional integration of Rho GTPases at the biological membranes are largely unclear. In this study, prenylated human Rac1, a prominent member of the Rho family, was purified in large amount from baculovirus-infected Spodoptera frugiperda insect cells using a systematic detergent screening. In contrast to non-prenylated human Rac1 purified from Escherichia coli, prenylated Rac1 from insect cells was able to associate with synthetic liposomes and to bind Rho-specific guanine nucleotide dissociation inhibitor 1 (GDI1). Subsequent liposome reconstitution experiments revealed that GDI1 efficiently extracts Rac1 from liposomes preferentially in the inactive GDP-bound state. The extraction was prevented when Rac1 was activated to its GTP-bound state by Rac-specific guanine nucleotide exchange factors (GEFs), such as Vav2, Dbl, Tiam1, P-Rex1 and TrioN, and bound by the downstream effector Pak1. We found that dissociation of Rac1-GDP from its complex with GDI1 strongly correlated with two distinct activities of especially Dbl and Tiam1, including liposome association and the GDP/GTP exchange. Taken together, our results provided first detailed insights into the advantages of the in vitro liposome-based reconstitution system to study both the integration of the signal transducing protein complexes and the mechanisms of regulation and signaling of small GTPases at biological membranes.
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Affiliation(s)
- Si-Cai Zhang
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
| | - Lothar Gremer
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
- Institute of Physical Biology, Heinrich-Heine University, Düsseldorf, Germany
- Institute of Complex Systems, ICS-6, Research Center Jülich GmbH, Jülich, Germany
| | - Henrike Heise
- Institute of Physical Biology, Heinrich-Heine University, Düsseldorf, Germany
- Institute of Complex Systems, ICS-6, Research Center Jülich GmbH, Jülich, Germany
| | - Petra Janning
- Department of Chemical Biology, Max-Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Aliaksei Shymanets
- Institute of Experimental and Clinical Pharmacology and Toxicology, Tübingen Medical School, Tübingen, Germany
| | - Ion C. Cirstea
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
- Leibniz Institute for Age Research, Jena, Germany
| | - Eberhard Krause
- Laboratory of Mass Spectrometry, Leibniz Institute of Molecular Pharmacology, Berlin, Germany
| | - Bernd Nürnberg
- Institute of Experimental and Clinical Pharmacology and Toxicology, Tübingen Medical School, Tübingen, Germany
| | - Mohammad Reza Ahmadian
- Institute of Biochemistry and Molecular Biology II, Medical Faculty of the Heinrich-Heine University, Düsseldorf, Germany
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19
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Moissoglu K, Schwartz MA. Spatial and temporal control of Rho GTPase functions. CELLULAR LOGISTICS 2014; 4:e943618. [PMID: 25610718 PMCID: PMC4279778 DOI: 10.4161/21592780.2014.943618] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 07/02/2014] [Indexed: 11/19/2022]
Abstract
Rho family GTPases control almost every aspect of cell physiology and, since their discovery, a wealth of knowledge has accumulated about their biochemical regulation and function. However, each Rho GTPase distributes between multiple cellular compartments, even within the same cell, where they are controlled by multiple regulators and signal to multiple effectors. Thus, major questions about spatial and temporal aspects of regulation remain unanswered. In particular, what are the nano-scale dynamics for their activation, membrane targeting, diffusion, effector activation and GTPase inactivation? How do these mechanisms differ in the different cellular compartments where Rho GTPases function? Addressing these complex aspects of Rho GTPase biology will significantly advance our understanding of the spatial and temporal control of cellular functions.
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Affiliation(s)
- Konstadinos Moissoglu
- Laboratory of Cellular and Molecular Biology; Center for Cancer Research; National Cancer Institute; National Institutes of Health ; Bethesda, MD USA
| | - Martin Alexander Schwartz
- Yale Cardiovascular Research Center and Departments of Medicine (Cardiology); Cell Biology and Biomedical Engineering; Yale School of Medicine ; New Haven, CT USA
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20
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Pick E. Role of the Rho GTPase Rac in the activation of the phagocyte NADPH oxidase: outsourcing a key task. Small GTPases 2014; 5:e27952. [PMID: 24598074 PMCID: PMC4114928 DOI: 10.4161/sgtp.27952] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 01/10/2014] [Accepted: 01/22/2014] [Indexed: 11/19/2022] Open
Abstract
The superoxide-generating NADPH oxidase of phagocytes consists of the membrane-associated cytochrome b 558 (a heterodimer of Nox2 and p22(phox)) and 4 cytosolic components: p47(phox), p67(phox), p40(phox), and the small GTPase, Rac, in complex with RhoGDI. Superoxide is produced by the NADPH-driven reduction of molecular oxygen, via a redox gradient located in Nox2. Electron flow in Nox2 is initiated by interaction with cytosolic components, which translocate to the membrane, p67(phox) playing the central role. The participation of Rac is expressed in the following sequence: (1) Translocation of the RacGDP-RhoGDI complex to the membrane; (2) Dissociation of RacGDP from RhoGDI; (3) GDP to GTP exchange on Rac, mediated by a guanine nucleotide exchange factor; (4) Binding of RacGTP to p67(phox); (5) Induction of a conformational change in p67(phox), promoting interaction with Nox2. The particular involvement of Rac in NADPH oxidase assembly serves as a paradigm for signaling by Rho GTPases, in general.
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Affiliation(s)
- Edgar Pick
- Julius Friedrich Cohnheim Laboratory of Phagocyte Research; Department of Clinical Microbiology and Immunology; Sackler School of Medicine; Tel Aviv University; Tel Aviv, Israel
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21
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Freisinger T, Klünder B, Johnson J, Müller N, Pichler G, Beck G, Costanzo M, Boone C, Cerione RA, Frey E, Wedlich-Söldner R. Establishment of a robust single axis of cell polarity by coupling multiple positive feedback loops. Nat Commun 2013; 4:1807. [PMID: 23651995 PMCID: PMC3674238 DOI: 10.1038/ncomms2795] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 03/22/2013] [Indexed: 01/06/2023] Open
Abstract
Establishment of cell polarity—or symmetry breaking—relies on local accumulation of polarity regulators. Although simple positive feedback is sufficient to drive symmetry breaking, it is highly sensitive to stochastic fluctuations typical for living cells. Here, by integrating mathematical modelling with quantitative experimental validations, we show that in the yeast Saccharomyces cerevisiae a combination of actin- and guanine nucleotide dissociation inhibitor-dependent recycling of the central polarity regulator Cdc42 is needed to establish robust cell polarity at a single site during yeast budding. The guanine nucleotide dissociation inhibitor pathway consistently generates a single-polarization site, but requires Cdc42 to cycle rapidly between its active and inactive form, and is therefore sensitive to perturbations of the GTPase cycle. Conversely, actin-mediated recycling of Cdc42 induces robust symmetry breaking but cannot restrict polarization to a single site. Our results demonstrate how cells optimize symmetry breaking through coupling between multiple feedback loops. A positive feedback loop which results in localized accumulation of the small GTPase Cdc42 generates cell polarity in budding yeast; however, such loops are inherently susceptible to noise. Here the authors demonstrate how two pathways that mediate Cdc42 recycling work together to ensure the robustness of symmetry breaking.
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Affiliation(s)
- Tina Freisinger
- Max-Planck-Institute of Biochemistry, Cellular Dynamics and Cell Patterning, Am Klopferspitz 18, D-82152 Martinsried, Germany
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22
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Klünder B, Freisinger T, Wedlich-Söldner R, Frey E. GDI-mediated cell polarization in yeast provides precise spatial and temporal control of Cdc42 signaling. PLoS Comput Biol 2013; 9:e1003396. [PMID: 24348237 PMCID: PMC3861033 DOI: 10.1371/journal.pcbi.1003396] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 10/31/2013] [Indexed: 01/19/2023] Open
Abstract
Cell polarization is a prerequisite for essential processes such as cell migration, proliferation or differentiation. The yeast Saccharomyces cerevisiae under control of the GTPase Cdc42 is able to polarize without the help of cytoskeletal structures and spatial cues through a pathway depending on its guanine nucleotide dissociation inhibitor (GDI) Rdi1. To develop a fundamental understanding of yeast polarization we establish a detailed mechanistic model of GDI-mediated polarization. We show that GDI-mediated polarization provides precise spatial and temporal control of Cdc42 signaling and give experimental evidence for our findings. Cell cycle induced changes of Cdc42 regulation enhance positive feedback loops of active Cdc42 production, and thereby allow simultaneous switch-like regulation of focused polarity and Cdc42 activation. This regulation drives the direct formation of a unique polarity cluster with characteristic narrowing dynamics, as opposed to the previously proposed competition between transient clusters. As the key components of the studied system are conserved among eukaryotes, we expect our findings also to apply to cell polarization in other organisms. Cell polarization is a fundamental cellular process that defines a single orientation axis within prokaryotic or eukaryotic cells and is a prerequisite for developmental processes such as cell migration, proliferation or differentiation. In the yeast Saccharomyces cerevisiae cell polarization determines the position of a new growth or bud site. Although many studies have focused on identifying polarity regulators and their interactions, the fundamental mechanisms and features of cell polarity still remain controversial. Here, we develop a detailed mathematical model of diffusion-driven cell polarization, which we verify experimentally. We show that this polarization mechanism provides precise spatial and temporal control of signals, which determine the place of a new growth site. Changes induced by the cell cycle allow simultaneous switch-like regulation of polarization and activation of the GTPase Cdc42, the central polarity regulator which initiates formation of a new bud. This regulation drives direct formation of a unique Cdc42 cluster with characteristic narrowing dynamics and robustly narrow spatial focus. Hence, our analysis reveals fundamental design principles that allow cell polarization to reliably initiate developmental processes at a specific time and place. As the key components of the studied system are conserved among eukaryotes, we expect our findings also to apply to cell polarization in other organisms.
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Affiliation(s)
- Ben Klünder
- Arnold Sommerfeld Center for Theoretical Physics (ASC) and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, München, Germany
| | - Tina Freisinger
- Max Planck Institute of Biochemistry, Cellular Dynamics and Cell Patterning, Martinsried, Germany
| | - Roland Wedlich-Söldner
- Max Planck Institute of Biochemistry, Cellular Dynamics and Cell Patterning, Martinsried, Germany
- * E-mail: (RWS); (EF)
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics (ASC) and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, München, Germany
- * E-mail: (RWS); (EF)
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23
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Ueyama T, Son J, Kobayashi T, Hamada T, Nakamura T, Sakaguchi H, Shirafuji T, Saito N. Negative charges in the flexible N-terminal domain of Rho GDP-dissociation inhibitors (RhoGDIs) regulate the targeting of the RhoGDI-Rac1 complex to membranes. THE JOURNAL OF IMMUNOLOGY 2013; 191:2560-9. [PMID: 23918979 DOI: 10.4049/jimmunol.1300209] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In its resting state, Rho GDP-dissociation inhibitor (RhoGDI) α forms a soluble cytoplasmic heterodimer with the GDP-bound form of Rac. Upon stimulation, the dissociation of RhoGDIα from the RhoGDIα-Rac complex is a mandatory step for Rac activation; however, this mechanism is poorly understood. In this study, we examined how the cytoplasm/membrane cycles of the RhoGDI-Rac complex are regulated, as well as where RhoGDI dissociates from the RhoGDI-Rac complex, during FcγR-mediated phagocytosis. The negatively charged and flexible N terminus (25 residues) of RhoGDIα, particularly its second negative amino acid cluster possessing five negatively charged amino acids, was a pivotal regulator in the cytoplasm/membrane cycles of the RhoGDI-Rac complex. We also found that RhoGDIα translocated to the phagosomes as a RhoGDIα-Rac1 complex, and this translocation was mediated by an interaction between the polybasic motif in the C terminus of Rac1 and anionic phospholipids produced on phagosomes, such as phosphatidic acid, that is, by a phagosome-targeting mechanism of Rac1. Thus, we demonstrated that the targeting/accumulation of the RhoGDIα-Rac1 complex to phagosomes is regulated by a balance between three factors: 1) the negatively charged and flexible N-terminal of RhoGDIα, 2) the binding affinity of RhoGDIα for Rac1, and 3) anionic phospholipids produced on phagosomes. Moreover, we demonstrated that the mechanism of targeting/accumulation of the RhoGDIα-Rac1 complex is also applicable for the RhoGDIβ-Rac1 complex.
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Affiliation(s)
- Takehiko Ueyama
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan.
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24
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Natarajan V, Dudek SM, Jacobson JR, Moreno-Vinasco L, Huang LS, Abassi T, Mathew B, Zhao Y, Wang L, Bittman R, Weichselbaum R, Berdyshev E, Garcia JGN. Sphingosine-1-phosphate, FTY720, and sphingosine-1-phosphate receptors in the pathobiology of acute lung injury. Am J Respir Cell Mol Biol 2013; 49:6-17. [PMID: 23449739 PMCID: PMC3727889 DOI: 10.1165/rcmb.2012-0411tr] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 12/26/2012] [Indexed: 12/23/2022] Open
Abstract
Acute lung injury (ALI) attributable to sepsis or mechanical ventilation and subacute lung injury because of ionizing radiation (RILI) share profound increases in vascular permeability as a key element and a common pathway driving increased morbidity and mortality. Unfortunately, despite advances in the understanding of lung pathophysiology, specific therapies do not yet exist for the treatment of ALI or RILI, or for the alleviation of unremitting pulmonary leakage, which serves as a defining feature of the illness. A critical need exists for new mechanistic insights that can lead to novel strategies, biomarkers, and therapies to reduce lung injury. Sphingosine 1-phosphate (S1P) is a naturally occurring bioactive sphingolipid that acts extracellularly via its G protein-coupled S1P1-5 as well as intracellularly on various targets. S1P-mediated cellular responses are regulated by the synthesis of S1P, catalyzed by sphingosine kinases 1 and 2, and by the degradation of S1P mediated by lipid phosphate phosphatases, S1P phosphatases, and S1P lyase. We and others have demonstrated that S1P is a potent angiogenic factor that enhances lung endothelial cell integrity and an inhibitor of vascular permeability and alveolar flooding in preclinical animal models of ALI. In addition to S1P, S1P analogues such as 2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol (FTY720), FTY720 phosphate, and FTY720 phosphonates offer therapeutic potential in murine models of lung injury. This translational review summarizes the roles of S1P, S1P analogues, S1P-metabolizing enzymes, and S1P receptors in the pathophysiology of lung injury, with particular emphasis on the development of potential novel biomarkers and S1P-based therapies for ALI and RILI.
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25
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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26
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Falkenberg CV, Loew LM. Computational analysis of Rho GTPase cycling. PLoS Comput Biol 2013; 9:e1002831. [PMID: 23326220 PMCID: PMC3542069 DOI: 10.1371/journal.pcbi.1002831] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 10/22/2012] [Indexed: 01/05/2023] Open
Abstract
The Rho family of GTPases control actin organization during diverse cellular responses (migration, cytokinesis and endocytosis). Although the primary members of this family (RhoA, Rac and Cdc42) have different downstream effects on actin remodeling, the basic mechanism involves targeting to the plasma membrane and activation by GTP binding. Our hypothesis is that the details of GTPase cycling between membrane and cytosol are key to the differential upstream regulation of these biochemical switches. Accordingly, we developed a modeling framework to analyze experimental data for these systems. This analysis can reveal details of GDI-mediated cycling and help distinguish between GDI-dependent and -independent mechanisms, including vesicle trafficking and direct association-dissociation of GTPase with membrane molecules. Analysis of experimental data for Rac membrane cycling reveals that the lower apparent affinity of GDI for RacGTP compared to RacGDP can be fully explained by the faster dissociation of the latter from the membrane. Non-dimensional steady-state solutions for membrane fraction of GTPase are presented in multidimensional charts. This methodology is then used to analyze glucose stimulated Rac cycling in pancreatic β-cells. The charts are used to illustrate the effects of GEFs/GAPs and regulated affinities between GTPases and membrane and/or GDI on the amount of membrane bound GTPase. In a similar fashion, the charts can be used as a guide in assessing how targeted modifications may compensate for altered GTPase-GDI balance in disease scenarios. Among the functions of the small GTPases Rac, RhoA and Cdc42 are the regulation of protein traffic, insulin secretion, cell shape, survival and motility. The last two are important steps for tumor growth and metastasis. The function of these proteins relies on their expression levels, proper membrane localization and activation. In addition, all three proteins compete for the same protein ‘GDI’, which modulates their cycling. These proteins are ubiquitous in mammalian cells, but also studied in simpler in vitro systems and cultured yeast. Here we show, using a series of computational analyses, that for each of these experimental systems the dominant pathway for membrane cycling of GTPases seems to differ. This means that the researcher interested in the physiological function of any of those proteins must make sure that the experimental system is appropriate. We present a methodology to identify the dominant pathways by measuring the apparent membrane dissociation rate of the protein as a function of GDI concentration. We provide charts generated from parametric scans. This analysis is then applied to the Rac-dependent insulin secretion pathway in pancreatic ß-cells, revealing that direct signaling between Rac and the membrane is an essential mechanism that emerges from the data.
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Affiliation(s)
- Cibele Vieira Falkenberg
- Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Leslie M. Loew
- Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut, United States of America
- * E-mail:
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Tnimov Z, Guo Z, Gambin Y, Nguyen UTT, Wu YW, Abankwa D, Stigter A, Collins BM, Waldmann H, Goody RS, Alexandrov K. Quantitative analysis of prenylated RhoA interaction with its chaperone, RhoGDI. J Biol Chem 2012; 287:26549-62. [PMID: 22628549 DOI: 10.1074/jbc.m112.371294] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Small GTPases of the Rho family regulate cytoskeleton remodeling, cell polarity, and transcription, as well as the cell cycle, in eukaryotic cells. Membrane delivery and recycling of the Rho GTPases is mediated by Rho GDP dissociation inhibitor (RhoGDI), which forms a stable complex with prenylated Rho GTPases. We analyzed the interaction of RhoGDI with the active and inactive forms of prenylated and unprenylated RhoA. We demonstrate that RhoGDI binds the prenylated form of RhoA·GDP with unexpectedly high affinity (K(d) = 5 pm). The very long half-life of the complex is reduced 25-fold on RhoA activation, with a concomitant reduction in affinity (K(d) = 3 nm). The 2.8-Å structure of the RhoA·guanosine 5'-[β,γ-imido] triphosphate (GMPPNP)·RhoGDI complex demonstrated that complex formation forces the activated RhoA into a GDP-bound conformation in the absence of nucleotide hydrolysis. We demonstrate that membrane extraction of Rho GTPase by RhoGDI is a thermodynamically favored passive process that operates through a series of progressively tighter intermediates, much like the one that is mediated by RabGDI.
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Affiliation(s)
- Zakir Tnimov
- Department of Molecular Cell Biology, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
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28
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Garcia-Mata R, Boulter E, Burridge K. The 'invisible hand': regulation of RHO GTPases by RHOGDIs. Nat Rev Mol Cell Biol 2011; 12:493-504. [PMID: 21779026 DOI: 10.1038/nrm3153] [Citation(s) in RCA: 411] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The 'invisible hand' is a term originally coined by Adam Smith in The Theory of Moral Sentiments to describe the forces of self-interest, competition and supply and demand that regulate the resources in society. This metaphor continues to be used by economists to describe the self-regulating nature of a market economy. The same metaphor can be used to describe the RHO-specific guanine nucleotide dissociation inhibitor (RHOGDI) family, which operates in the background, as an invisible hand, using similar forces to regulate the RHO GTPase cycle.
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Affiliation(s)
- Rafael Garcia-Mata
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 USA.
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29
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Usatyuk PV, He D, Bindokas V, Gorshkova IA, Berdyshev EV, Garcia JGN, Natarajan V. Photolysis of caged sphingosine-1-phosphate induces barrier enhancement and intracellular activation of lung endothelial cell signaling pathways. Am J Physiol Lung Cell Mol Physiol 2011; 300:L840-50. [PMID: 21478254 DOI: 10.1152/ajplung.00404.2010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that mediates cellular functions by ligation via G protein-coupled S1P receptors. In addition to its extracellular action, S1P also has intracellular effects; however, the signaling pathways modulated by intracellular S1P remain poorly defined. We have previously demonstrated a novel pathway of intracellular S1P generation in human lung endothelial cells (ECs). In the present study, we examined the role of intracellular S1P generated by photolysis of caged S1P on EC barrier regulation and signal transduction. Intracellular S1P released from caged S1P caused mobilization of intracellular calcium, induced activation of MAPKs, redistributed cortactin, vascular endothelial cadherin, and β-catenin to cell periphery, and tightened endothelial barrier in human pulmonary artery ECs. Treatment of cells with pertussis toxin (PTx) had no effect on caged S1P-mediated effects on Ca(2+) mobilization, reorganization of cytoskeleton, cell adherens junction proteins, and barrier enhancement; however, extracellular S1P effects were significantly attenuated by PTx. Additionally, intracellular S1P also activated small GTPase Rac1 and its effector Ras GTPase-activating-like protein IQGAP1, suggesting involvement of these proteins in the S1P-mediated changes in cell-to-cell adhesion contacts. Downregulation of sphingosine kinase 1 (SphK1), but not SphK2, with siRNA or inhibition of SphK activity with an inhibitor 2-(p-hydroxyanilino)-4-(p-chlorophenyl) thiazole (CII) attenuated exogenously administrated S1P-induced EC permeability. Furthermore, S1P1 receptor inhibitor SB649164 abolished exogenous S1P-induced transendothelial resistance changes but had no effect on intracellular S1P generated by photolysis of caged S1P. These results provide evidence that intracellular S1P modulates signal transduction in lung ECs via signaling pathway(s) independent of S1P receptors.
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Affiliation(s)
- Peter V Usatyuk
- Department of Pharmacology, University of Illinois at Chicago, 60612, USA
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Bhagatji P, Leventis R, Rich R, Lin CJ, Silvius JR. Multiple cellular proteins modulate the dynamics of K-ras association with the plasma membrane. Biophys J 2011; 99:3327-35. [PMID: 21081081 DOI: 10.1016/j.bpj.2010.10.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 09/21/2010] [Accepted: 10/04/2010] [Indexed: 10/18/2022] Open
Abstract
Although specific proteins have been identified that regulate the membrane association and facilitate intracellular transport of prenylated Rho- and Rab-family proteins, it is not known whether cellular proteins fulfill similar roles for other prenylated species, such as Ras-family proteins. We used a previously described method to evaluate how several cellular proteins, previously identified as potential binding partners (but not effectors) of K-ras4B, influence the dynamics of K-ras association with the plasma membrane. Overexpression of either PDEδ or PRA1 enhances, whereas knockdown of either protein reduces, the rate of dissociation of K-ras from the plasma membrane. Inhibition of calmodulin likewise reduces the rate of K-ras dissociation from the plasma membrane, in this case in a manner specific for the activated form of K-ras. By contrast, galectin-3 specifically reduces the rate of plasma membrane dissociation of activated K-ras, an effect that is blocked by the K-ras antagonist farnesylthiosalicylic acid (salirasib). Multiple cellular proteins thus control the dynamics of membrane association and intercompartmental movement of K-ras to an important degree even under basal cellular conditions.
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Affiliation(s)
- Pinkesh Bhagatji
- Department of Biochemistry, McGill University, Montréal, Québec, Canada
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31
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Ischebeck T, Stenzel I, Hempel F, Jin X, Mosblech A, Heilmann I. Phosphatidylinositol-4,5-bisphosphate influences Nt-Rac5-mediated cell expansion in pollen tubes of Nicotiana tabacum. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 65:453-68. [PMID: 21265898 DOI: 10.1111/j.1365-313x.2010.04435.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The regulation of pollen tube growth by the phospholipid phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P(2) ) is not well understood. The Arabidopsis genome encodes two type A phosphatidylinositol-4-phosphate (PI4P) 5-kinases, PIP5K10 and PIP5K11, which are exclusively expressed in pollen and produce PtdIns(4,5)P(2) in vitro. Fluorescence-tagged PIP5K10 and PIP5K11 localized to lateral subapical plasma membrane microdomains in tobacco pollen tubes in a pattern closely resembling the distribution of PtdIns(4,5)P(2,) with the exception of notably weaker association at the extreme apex. Overexpression of PIP5K10 or PIP5K11 in tobacco pollen tubes resulted in severe tip swelling and altered actin fine structure similar to that reported for overexpression of tobacco Nt-Rac5, a monomeric GTPase known to regulate the actin cytoskeleton. Increased sensitivity of Arabidopsis pip5k10 pip5k11 double mutant pollen tubes to Latrunculin B (LatB) further supports a role for type A PI4P 5-kinases in controlling the actin cytoskeleton. Despite the disruption of both its type A PI4P 5-kinases, the pip5k10 pip5k11 double mutant was fertile, indicating that one of the remaining type B PI4P 5-kinase isoforms might be functionally redundant with PIP5K10 and PIP5K11. Antagonistic effects of PIP5K11 and the Nt-Rac5-specific guanine nucleotide dissociation inhibitor, Nt-RhoGDI2, on tip swelling observed in coexpression-titration experiments indicate a link between PtdIns(4,5)P(2) and Rac-signaling in pollen tubes. The data suggest that type A PI4P 5-kinases influence the actin cytoskeleton in pollen tubes in part by counteracting Nt-RhoGDI2, possibly contributing to the control of the pool of plasma membrane-associated Nt-Rac5.
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Affiliation(s)
- Till Ischebeck
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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32
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Neubrand VE, Thomas C, Schmidt S, Debant A, Schiavo G. Kidins220/ARMS regulates Rac1-dependent neurite outgrowth by direct interaction with the RhoGEF Trio. J Cell Sci 2010; 123:2111-23. [PMID: 20519585 DOI: 10.1242/jcs.064055] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neurite extension depends on extracellular signals that lead to changes in gene expression and rearrangement of the actin cytoskeleton. A factor that might orchestrate these signalling pathways with cytoskeletal elements is the integral membrane protein Kidins220/ARMS, a downstream target of neurotrophins. Here, we identified Trio, a RhoGEF for Rac1, RhoG and RhoA, which is involved in neurite outgrowth and axon guidance, as a binding partner of Kidins220. This interaction is direct and occurs between the N-terminus of Trio and the ankyrin repeats of Kidins220. Trio and Kidins220 colocalise at the tips of neurites in NGF-differentiated PC12 cells, where F-actin and Rac1 also accumulate. Expression of the ankyrin repeats of Kidins220 in PC12 cells inhibits NGF-dependent and Trio-induced neurite outgrowth. Similar results are seen in primary hippocampal neurons. Our data indicate that Kidins220 might localise Trio to specific membrane sites and regulate its activity, leading to Rac1 activation and neurite outgrowth.
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Affiliation(s)
- Veronika E Neubrand
- Molecular NeuroPathobiology, Cancer Research UK London Research Institute, London, UK.
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Abstract
Reactive oxygen species (ROS) have been implicated in many intra- and intercellular processes. High levels of ROS are generated as part of the innate immunity in the respiratory burst of phagocytic cells. Low levels of ROS, however, are generated in a highly controlled manner by various cell types to act as second messengers in redox-sensitive pathways. A NADPH oxidase has been initially described as the respiratory burst enzyme in neutrophils. Stimulation of this complex enzyme system requires specific signaling cascades linking it to membrane-receptor activation. Subsequently, a family of NADPH oxidases has been identified in various nonphagocytic cells. They mainly differ in containing one out of seven homologous catalytic core proteins termed NOX1 to NOX5 and DUOX1 or 2. NADPH oxidase activity is controlled by regulatory subunits, including the NOX regulators p47phox and p67phox, their homologs NOXO1 and NOXA1, or the DUOX1 or 2 regulators DUOXA1 and 2. In addition, the GTPase Rac modulates activity of several of these enzymes. Recently, additional proteins have been identified that seem to have a regulatory function on NADPH oxidase activity under certain conditions. We will thus summarize molecular pathways linking activation of different membrane-bound receptors with increased ROS production of NADPH oxidases.
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Affiliation(s)
- Andreas Petry
- Experimental Pediatric Cardiology, Technical University Munich, Munich, Germany
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Mizrahi A, Berdichevsky Y, Casey PJ, Pick E. A prenylated p47phox-p67phox-Rac1 chimera is a Quintessential NADPH oxidase activator: membrane association and functional capacity. J Biol Chem 2010; 285:25485-99. [PMID: 20529851 DOI: 10.1074/jbc.m110.113779] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The superoxide-generating NADPH oxidase complex of resting phagocytes includes cytochrome b(559), a membrane-associated heterodimer composed of two subunits (Nox2 and p22(phox)), and four cytosolic proteins (p47(phox), p67(phox), Rac, and p40(phox)). Upon stimulation, the cytosolic components translocate to the membrane, as the result of a series of interactions among the cytosolic components and among the cytosolic components and cytochrome b(559) and its phospholipid environment. We described the construction of a tripartite chimera (trimera) consisting of strategic domains of p47(phox), p67(phox), and Rac1, in which interactions among cytosolic components were replaced by fusion (Berdichevsky, Y., Mizrahi, A., Ugolev, Y., Molshanski-Mor, S., and Pick, E. (2007) J. Biol. Chem. 282, 22122-22139). We now fused green fluorescent protein (GFP) to the N terminus of the trimera and found the following. 1) The GFP-p47(phox)-p67(phox)-Rac1 trimera activates the oxidase in amphiphile-dependent and -independent (anionic phospholipid-enriched membrane) cell-free systems. 2) Geranylgeranylation of the GFP-trimera makes it a potent oxidase activator in unmodified (native) membranes and in the absence of amphiphile. 3) Prenylated GFP-trimera binds spontaneously to native membranes (as assessed by gel filtration and in-line fluorometry), forming a tight complex capable of NADPH-dependent, activator-independent superoxide production at rates similar to those measured in canonical cell-free systems. 4) Prenylation of the GFP-trimera supersedes completely the dependence of oxidase activation on the p47(phox) phox homology domain and, partially, on the Rac1 polybasic domain, but the requirement for Trp(193) in p47(phox) persists. Prenylated GFP-p47(phox)-p67(phox)-Rac1 trimera acts as a quintessential single molecule oxidase activator of potential use in high throughput screening of inhibitors.
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Affiliation(s)
- Ariel Mizrahi
- Julius Friedrich Cohnheim Laboratory of Phagocyte Research, Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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Rajagopal S, Ji Y, Xu K, Li Y, Wicks K, Liu J, Wong KW, Herman IM, Isberg RR, Buchsbaum RJ. Scaffold proteins IRSp53 and spinophilin regulate localized Rac activation by T-lymphocyte invasion and metastasis protein 1 (TIAM1). J Biol Chem 2010; 285:18060-71. [PMID: 20360004 DOI: 10.1074/jbc.m109.051490] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Rac exchange factor Tiam1 is involved in diverse cell functions and signaling pathways through multiple protein interactions, raising the question of how signaling and functional specificity are achieved. We have shown that Tiam1 interactions with different scaffold proteins activate different Rac-dependent pathways by recruiting specific Rac effector proteins, and reasoned that there must be regulatory mechanisms governing each interaction. Fibroblasts express at least two Tiam1-interacting proteins, insulin receptor substrate protein 53 kDa (IRSp53) and spinophilin. We used fluorescent resonance energy transfer (FRET) to measure localized Rac activation associated with IRSp53 and spinophilin complexes in individual fibroblasts to test this hypothesis. Pervanadate or platelet-derived growth factor induced localized Rac activation dependent on Tiam1 and IRSp53. Forskolin or epinephrine induced localized Rac activation dependent on Tiam1 and spinophilin. In spinophilin-deficient cells, Tiam1 co-localized with IRSp53 in response to pervanadate or platelet-derived growth factor. In IRSp53-deficient cells, Tiam1 co-localized with spinophilin in response to forskolin or epinephrine. Total cellular levels of activated Rac were affected only in cells with exogenous Tiam1, and were primarily increased in the membrane fraction. Downstream effects of Rac activation were also stimulus and scaffold-specific. Cell ruffling, spreading, and cell adhesion were dependent on IRSp53, but not spinophilin. Epinephrine decreased IRSp53-dependent adhesion and increased cell migration in a Rac and spinophilin-dependent fashion. These results support the idea that Tiam1 interactions with different scaffold proteins couple distinct upstream signals to localized Rac activation and specific downstream pathways, and suggest that manipulating Tiam1-scaffold interactions can modulate Rac-dependent cellular behaviors.
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Affiliation(s)
- Soumitra Rajagopal
- Molecular Oncology Research Institute, Tufts Medical Center, Tufts UniversitySackler School of Graduate Biomedical Sciences, Boston, Massachusetts 02111, USA
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36
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Usatyuk PV, Gorshkova IA, He D, Zhao Y, Kalari SK, Garcia JGN, Natarajan V. Phospholipase D-mediated activation of IQGAP1 through Rac1 regulates hyperoxia-induced p47phox translocation and reactive oxygen species generation in lung endothelial cells. J Biol Chem 2009; 284:15339-52. [PMID: 19366706 DOI: 10.1074/jbc.m109.005439] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidic acid generated by the activation of phospholipase D (PLD) functions as a second messenger and plays a vital role in cell signaling. Here we demonstrate that PLD-dependent generation of phosphatidic acid is critical for Rac1/IQGAP1 signal transduction, translocation of p47(phox) to cell periphery, and ROS production. Exposure of [(32)P]orthophosphate-labeled human pulmonary artery endothelial cells (HPAECs) to hyperoxia (95% O(2) and 5% CO(2)) in the presence of 0.05% 1-butanol, but not tertiary-butanol, stimulated PLD as evidenced by accumulation of [(32)P]phosphatidylbutanol. Infection of HPAECs with adenoviral constructs of PLD1 and PLD2 wild-type potentiated hyperoxia-induced PLD activation and accumulation of O(2)(.)/reactive oxygen species (ROS). Conversely, overexpression of catalytically inactive mutants of PLD (hPLD1-K898R or mPLD2-K758R) or down-regulation of expression of PLD with PLD1 or PLD2 siRNA did not augment hyperoxia-induced [(32)P]phosphatidylbutanol accumulation and ROS generation. Hyperoxia caused rapid activation and redistribution of Rac1, and IQGAP1 to cell periphery, and down-regulation of Rac1, and IQGAP1 attenuated hyperoxia-induced tyrosine phosphorylation of Src and cortactin and ROS generation. Further, hyperoxia-mediated redistribution of Rac1, and IQGAP1 to membrane ruffles, was attenuated by PLD1 or PLD2 small interference RNA, suggesting that PLD is upstream of the Rac1/IQGAP1 signaling cascade. Finally, small interference RNA for PLD1 or PLD2 attenuated hyperoxia-induced cortactin tyrosine phosphorylation and abolished Src, cortactin, and p47(phox) redistribution to cell periphery. These results demonstrate a role of PLD in hyperoxia-mediated IQGAP1 activation through Rac1 in tyrosine phosphorylation of Src and cortactin, as well as in p47(phox) translocation and ROS formation in human lung endothelial cells.
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Affiliation(s)
- Peter V Usatyuk
- Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA
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