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Haspinger DC, Klinge S, Holzapfel GA. Numerical analysis of the impact of cytoskeletal actin filament density alterations onto the diffusive vesicle-mediated cell transport. PLoS Comput Biol 2021; 17:e1008784. [PMID: 33939706 PMCID: PMC8130967 DOI: 10.1371/journal.pcbi.1008784] [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: 09/07/2020] [Revised: 05/18/2021] [Accepted: 02/09/2021] [Indexed: 11/21/2022] Open
Abstract
The interior of a eukaryotic cell is a highly complex composite material which consists of water, structural scaffoldings, organelles, and various biomolecular solutes. All these components serve as obstacles that impede the motion of vesicles. Hence, it is hypothesized that any alteration of the cytoskeletal network may directly impact or even disrupt the vesicle transport. A disruption of the vesicle-mediated cell transport is thought to contribute to several severe diseases and disorders, such as diabetes, Parkinson’s and Alzheimer’s disease, emphasizing the clinical relevance. To address the outlined objective, a multiscale finite element model of the diffusive vesicle transport is proposed on the basis of the concept of homogenization, owed to the complexity of the cytoskeletal network. In order to study the microscopic effects of specific nanoscopic actin filament network alterations onto the vesicle transport, a parametrized three-dimensional geometrical model of the actin filament network was generated on the basis of experimentally observed filament densities and network geometries in an adenocarcinomic human alveolar basal epithelial cell. Numerical analyzes of the obtained effective diffusion properties within two-dimensional sampling domains of the whole cell model revealed that the computed homogenized diffusion coefficients can be predicted statistically accurate by a simple two-parameter power law as soon as the inaccessible area fraction, due to the obstacle geometries and the finite size of the vesicles, is known. This relationship, in turn, leads to a massive reduction in computation time and allows to study the impact of a variety of different cytoskeletal alterations onto the vesicle transport. Hence, the numerical simulations predicted a 35% increase in transport time due to a uniformly distributed four-fold increase of the total filament amount. On the other hand, a hypothetically reduced expression of filament cross-linking proteins led to sparser filament networks and, thus, a speed up of the vesicle transport. Many vital processes in our eukaryotic cells and organs require an astonishingly precise routing of intermediate products to various intra- and extracellular destinations using vesicles as transporters. This can be illustrated by numerous examples, such as the production and destruction of proteins, the export of neurotransmitters or insulin to the extracellular domain, etc. However, the inside of a cell is tightly packed with numerous structural scaffoldings (filaments), which serve as obstacles and impede the vesicle motion. It is thought that any disturbances of the vesicle-mediated cell transport contribute to numerous degenerative diseases and disorders, which highlights the clinical relevance for investigating this intracellular transport mechanism by developing computational models and performing experimental studies. In this study, we numerically quantified how different specific alterations of the filament density inside a human lung cell—due to changed mechanical loadings or genetic disorders of proteins being responsible for filament branching—affect the diffusion of vesicles inside the intracellular fluid. Therefore, based on the concept of homogenization, a computationally efficient numerical method was developed and utilized to simulate the diffusion of vesicles inside the whole cell, considering the detailed structural information of the filament network.
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Affiliation(s)
| | - Sandra Klinge
- Chair of Structural Mechanics and Analysis, TU Berlin, Berlin, Germany
| | - Gerhard A. Holzapfel
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
- Faculty of Engineering Science and Technology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- * E-mail:
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Tachikawa M, Mochizuki A. Golgi apparatus self-organizes into the characteristic shape via postmitotic reassembly dynamics. Proc Natl Acad Sci U S A 2017; 114:5177-5182. [PMID: 28461510 PMCID: PMC5441826 DOI: 10.1073/pnas.1619264114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The Golgi apparatus is a membrane-bounded organelle with the characteristic shape of a series of stacked flat cisternae. During mitosis in mammalian cells, the Golgi apparatus is once fragmented into small vesicles and then reassembled to form the characteristic shape again in each daughter cell. The mechanism and details of the reassembly process remain elusive. Here, by the physical simulation of a coarse-grained membrane model, we reconstructed the three-dimensional morphological dynamics of the Golgi reassembly process. Considering the stability of the interphase Golgi shape, we introduce two hypothetical mechanisms-the Golgi rim stabilizer protein and curvature-dependent restriction on membrane fusion-into the general biomembrane model. We show that the characteristic Golgi shape is spontaneously organized from the assembly of vesicles by proper tuning of the two additional mechanisms, i.e., the Golgi reassembly process is modeled as self-organization. We also demonstrate that the fine Golgi shape forms via a balance of three reaction speeds: vesicle aggregation, membrane fusion, and shape relaxation. Moreover, the membrane fusion activity decreases thickness and the number of stacked cisternae of the emerging shapes.
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Affiliation(s)
- Masashi Tachikawa
- Theoretical Biology Laboratory, RIKEN, Wako 351-0198, Japan;
- Interdisciplinary Theoretical Science Research Group, RIKEN, Wako 351-0198, Japan
| | - Atsushi Mochizuki
- Theoretical Biology Laboratory, RIKEN, Wako 351-0198, Japan
- Interdisciplinary Theoretical Science Research Group, RIKEN, Wako 351-0198, Japan
- Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
- Interdisciplinary Theoretical and Mathematical Science Program, RIKEN, Wako 351-0198, Japan
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3
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Nonequilibrium description of de novo biogenesis and transport through Golgi-like cisternae. Sci Rep 2016; 6:38840. [PMID: 27991496 PMCID: PMC5171829 DOI: 10.1038/srep38840] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/11/2016] [Indexed: 12/11/2022] Open
Abstract
A central issue in cell biology is the physico-chemical basis of organelle biogenesis in intracellular trafficking pathways, its most impressive manifestation being the biogenesis of Golgi cisternae. At a basic level, such morphologically and chemically distinct compartments should arise from an interplay between the molecular transport and chemical maturation. Here, we formulate analytically tractable, minimalist models, that incorporate this interplay between transport and chemical progression in physical space, and explore the conditions for de novo biogenesis of distinct cisternae. We propose new quantitative measures that can discriminate between the various models of transport in a qualitative manner–this includes measures of the dynamics in steady state and the dynamical response to perturbations of the kind amenable to live-cell imaging.
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Suga K, Saito A, Mishima T, Akagawa K. ER and Golgi stresses increase ER-Golgi SNARE Syntaxin5: Implications for organelle stress and βAPP processing. Neurosci Lett 2015. [PMID: 26219982 DOI: 10.1016/j.neulet.2015.07.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Unresolved endoplasmic reticulum (ER) stress causes neuronal death and has been implicated in neurodegenerative conditions such as Alzheimer's disease (AD). However, the mechanisms by which stress signals propagate from the ER through the Golgi apparatus and their effects on the transport and processing of AD-related proteins, such as β-amyloid precursor protein (βAPP), are unknown. We recently found that in the NG108-15 cell line, ER stress upregulates ER-Golgi-soluble N-ethylmaleimide-sensitive factor-attachment protein receptors (ER-Golgi SNAREs) Syx5 and Bet1. In the present study, we examined the effects of apoptosis and ER stress inducers on the expression of ER-Golgi SNARE proteins and cell viability in a primary culture of rat hippocampal neurons. An apoptosis inducer significantly downregulated the expression of ER-Golgi SNARE Syx5. ER-stress inducers upregulated the expression of Syx5 isoforms and Bet1 proteins via de novo synthesis of their mRNA transcripts. Knockdown of Syx5 during apoptosis or ER stress induction enhanced vulnerability of neurons. Additionally, we examined the effects of Golgi stress on Syx5 expression and βAPP processing. Golgi stress also induced upregulation of ER-Golgi SNARE Syx5, and concomitantly, suppressed amyloid-β peptide secretion. These findings suggest that Syx5 is a potential stress responsive factor that participates in βAPP processing and the survival pathways of neuronal cells.
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Affiliation(s)
- Kei Suga
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo 181-8611, Japan.
| | - Ayako Saito
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo 181-8611, Japan
| | - Tatsuya Mishima
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo 181-8611, Japan
| | - Kimio Akagawa
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo 181-8611, Japan
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Gong H, Feng L. Computational analysis of the roles of ER-Golgi network in the cell cycle. BMC SYSTEMS BIOLOGY 2014; 8 Suppl 4:S3. [PMID: 25522186 PMCID: PMC4290691 DOI: 10.1186/1752-0509-8-s4-s3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND ER-Golgi network plays an important role in the processing, sorting and transport of proteins, and it's also a site for many signaling pathways that regulate the cell cycle. Accumulating evidence suggests that, the stressed ER and malfunction of Golgi apparatus are associated with the pathogenesis of cancer and Alzheimer's disease (AD). Our previous work discovered and verified that altering the expression levels of target SNARE and GEF could modulate the size of Golgi apparatus. Moreover, Golgi's structure and size undergo dramatic changes during the development of several diseases. It is of importance to investigate the roles of ER-Golgi network in the cell cycle progression and some diseases. RESULTS In this work, we first develop a computational model to study the ER stress-induced and Golgi-related apoptosis-survival signaling pathways. Then, we propose and apply both asynchronous and synchronous model checking methods, which extend our previous verification technique, to automatically and formally analyze the ER-Golgi-regulated signaling pathways in the cell cycle progression through verifying some computation tree temporal logic formulas. CONCLUSIONS The proposed asynchronous and synchronous verification technique has advantages for large network analysis and verification over traditional simulation methods. Using the model checking method, we verified several Alzheimer's disease and cancer-related properties, and also identified important proteins (NFκB, ATF4, ASK1 and TRAF2) in the ER-Golgi network, which might be responsible for the pathogenesis of cancer and AD. Our studies indicate that targeting the ER stress-induced and Golgi-related pathways might serve as potent therapeutic targets for the treatment of cancer and Alzheimer's disease.
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Cancino J, Capalbo A, Di Campli A, Giannotta M, Rizzo R, Jung JE, Di Martino R, Persico M, Heinklein P, Sallese M, Luini A. Control systems of membrane transport at the interface between the endoplasmic reticulum and the Golgi. Dev Cell 2014; 30:280-94. [PMID: 25117681 DOI: 10.1016/j.devcel.2014.06.018] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/08/2014] [Accepted: 06/23/2014] [Indexed: 10/24/2022]
Abstract
A fundamental property of cellular processes is to maintain homeostasis despite varying internal and external conditions. Within the membrane transport apparatus, variations in membrane fluxes from the endoplasmic reticulum (ER) to the Golgi complex are balanced by opposite fluxes from the Golgi to the ER to maintain homeostasis between the two organelles. Here we describe a molecular device that balances transport fluxes by integrating transduction cascades with the transport machinery. Specifically, ER-to-Golgi transport activates the KDEL receptor at the Golgi, which triggers a cascade that involves Gs and adenylyl cyclase and phosphodiesterase isoforms and then PKA activation and results in the phosphorylation of transport machinery proteins. This induces retrograde traffic to the ER and balances transport fluxes between the ER and Golgi. Moreover, the KDEL receptor activates CREB1 and other transcription factors that upregulate transport-related genes. Thus, a Golgi-based control system maintains transport homeostasis through both signaling and transcriptional networks.
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Affiliation(s)
- Jorge Cancino
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy; Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Quillota 980, Viña del Mar 2520000, Chile.
| | - Anita Capalbo
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Antonella Di Campli
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Monica Giannotta
- Consorzio Mario Negri Sud, Via Nazionale 8/A, 66030 Santa Maria Imbaro (Chieti), Italy
| | - Riccardo Rizzo
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Juan E Jung
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Istituto di Ricovero e Cura a Carattere Scientifico, Istituto di Ricerca Diagnostica e Nucleare (SDN), 80143 Napoli, Italy
| | - Rosaria Di Martino
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Maria Persico
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Istituto di Ricovero e Cura a Carattere Scientifico, Istituto di Ricerca Diagnostica e Nucleare (SDN), 80143 Napoli, Italy
| | - Petra Heinklein
- Institut für Biochemie Charité, Universitätsmedizin Berlin, CrossOver Charitéplatz 1/Sitz, Virchowweg 6, 10117 Berlin, Germany
| | - Michele Sallese
- Consorzio Mario Negri Sud, Via Nazionale 8/A, 66030 Santa Maria Imbaro (Chieti), Italy
| | - Alberto Luini
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy.
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7
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Ramadas R, Thattai M. New organelles by gene duplication in a biophysical model of eukaryote endomembrane evolution. Biophys J 2014; 104:2553-63. [PMID: 23746528 DOI: 10.1016/j.bpj.2013.03.066] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 03/05/2013] [Accepted: 03/11/2013] [Indexed: 12/13/2022] Open
Abstract
Extant eukaryotic cells have a dynamic traffic network that consists of diverse membrane-bound organelles exchanging matter via vesicles. This endomembrane system arose and diversified during a period characterized by massive expansions of gene families involved in trafficking after the acquisition of a mitochondrial endosymbiont by a prokaryotic host cell >1.8 billion years ago. Here we investigate the mechanistic link between gene duplication and the emergence of new nonendosymbiotic organelles, using a minimal biophysical model of traffic. Our model incorporates membrane-bound compartments, coat proteins and adaptors that drive vesicles to bud and segregate cargo from source compartments, and SNARE proteins and associated factors that cause vesicles to fuse into specific destination compartments. In simulations, arbitrary numbers of compartments with heterogeneous initial compositions segregate into a few compositionally distinct subsets that we term organelles. The global structure of the traffic system (i.e., the number, composition, and connectivity of organelles) is determined completely by local molecular interactions. On evolutionary timescales, duplication of the budding and fusion machinery followed by loss of cross-interactions leads to the emergence of new organelles, with increased molecular specificity being necessary to maintain larger organellar repertoires. These results clarify potential modes of early eukaryotic evolution as well as more recent eukaryotic diversification.
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Affiliation(s)
- Rohini Ramadas
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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8
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Dmitrieff S, Sens P. Transient domain formation in membrane-bound organelles undergoing maturation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:062704. [PMID: 24483483 DOI: 10.1103/physreve.88.062704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 08/25/2013] [Indexed: 06/03/2023]
Abstract
The membrane components of cellular organelles have been shown to segregate into domains as the result of biochemical maturation. We propose that the dynamical competition between maturation and lateral segregation of membrane components regulates domain formation. We study a two-component fluid membrane in which enzymatic reaction irreversibly converts one component into another and phase separation triggers the formation of transient membrane domains. The maximum domain size is shown to depend on the maturation rate as a power law similar to the one observed for domain growth with time in the absence of maturation, despite this time dependence not being verified in the case of irreversible maturation. This control of domain size by enzymatic activity could play a critical role in regulating exchange between organelles or within compartmentalized organelles such as the Golgi apparatus.
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Affiliation(s)
- Serge Dmitrieff
- Laboratoire Gulliver (CNRS UMR 7083) ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France
| | - Pierre Sens
- Laboratoire Gulliver (CNRS UMR 7083) ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France
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9
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Abstract
In this chapter, we summarize recent theoretical efforts to address a variety of issues in Golgi morphogenesis: de novo biogenesis of compartments with precise chemical identity, the transport of proteins through the Golgi, the maintenance of chemical identity, and the morphology of Golgi compartments, from the perspective of nonequilibrium physics.
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Affiliation(s)
- Pierre Sens
- Laboratoire Gulliver, CNRS-ESPCI, UMR 7083, 75231 Paris, France
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10
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Three-dimensional stochastic off-lattice model of binding chemistry in crowded environments. PLoS One 2012; 7:e30131. [PMID: 22272286 PMCID: PMC3260218 DOI: 10.1371/journal.pone.0030131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 12/14/2011] [Indexed: 01/01/2023] Open
Abstract
Molecular crowding is one of the characteristic features of the intracellular environment, defined by a dense mixture of varying kinds of proteins and other molecules. Interaction with these molecules significantly alters the rates and equilibria of chemical reactions in the crowded environment. Numerous fundamental activities of a living cell are strongly influenced by the crowding effect, such as protein folding, protein assembly and disassembly, enzyme activity, and signal transduction. Quantitatively predicting how crowding will affect any particular process is, however, a very challenging problem because many physical and chemical parameters act synergistically in ways that defy easy analysis. To build a more realistic model for this problem, we extend a prior stochastic off-lattice model from two-dimensional (2D) to three-dimensional (3D) space and examine how the 3D results compare to those found in 2D. We show that both models exhibit qualitatively similar crowding effects and similar parameter dependence, particularly with respect to a set of parameters previously shown to act linearly on total reaction equilibrium. There are quantitative differences between 2D and 3D models, although with a generally gradual nonlinear interpolation as a system is extended from 2D to 3D. However, the additional freedom of movement allowed to particles as thickness of the simulation box increases can produce significant quantitative change as a system moves from 2D to 3D. Simulation results over broader parameter ranges further show that the impact of molecular crowding is highly dependent on the specific reaction system examined.
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11
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Klann M, Koeppl H, Reuss M. Spatial modeling of vesicle transport and the cytoskeleton: the challenge of hitting the right road. PLoS One 2012; 7:e29645. [PMID: 22253752 PMCID: PMC3257240 DOI: 10.1371/journal.pone.0029645] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 12/02/2011] [Indexed: 01/15/2023] Open
Abstract
The membrane trafficking machinery provides a transport and sorting system for many cellular proteins. We propose a mechanistic agent-based computer simulation to integrate and test the hypothesis of vesicle transport embedded into a detailed model cell. The method tracks both the number and location of the vesicles. Thus both the stochastic properties due to the low numbers and the spatial aspects are preserved. The underlying molecular interactions that control the vesicle actions are included in a multi-scale manner based on the model of Heinrich and Rapoport (2005). By adding motor proteins we can improve the recycling process of SNAREs and model cell polarization. Our model also predicts that coat molecules should have a high turnover at the compartment membranes, while the turnover of motor proteins has to be slow. The modular structure of the underlying model keeps it tractable despite the overall complexity of the vesicle system. We apply our model to receptor-mediated endocytosis and show how a polarized cytoskeleton structure leads to polarized distributions in the plasma membrane both of SNAREs and the Ste2p receptor in yeast. In addition, we can couple signal transduction and membrane trafficking steps in one simulation, which enables analyzing the effect of receptor-mediated endocytosis on signaling.
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Affiliation(s)
- Michael Klann
- Automatic Control Laboratory, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland.
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12
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Gong H, Zuliani P, Komuravelli A, Faeder JR, Clarke EM. Computational Modeling and Verification of Signaling Pathways in Cancer. ALGEBRAIC AND NUMERIC BIOLOGY 2012. [DOI: 10.1007/978-3-642-28067-2_7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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13
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Bhalla US. Trafficking motifs as the basis for two-compartment signaling systems to form multiple stable states. Biophys J 2011; 101:21-32. [PMID: 21723811 DOI: 10.1016/j.bpj.2011.05.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 04/12/2011] [Accepted: 05/09/2011] [Indexed: 11/29/2022] Open
Abstract
Transport of molecules in cells is a central part of cell biology. Frequently such trafficking is not just for material transport, but also for information propagation, and serves to couple signaling circuits across cellular compartments. Here, I show that trafficking transforms simple local signaling pathways into self-organizing systems that span compartments and confer distinct states and identities to these compartments. I find that three motifs encapsulate the responses of most single-compartment signaling pathways in the context of trafficking. These motifs combine with different trafficking reactions to generate a diverse set of cellular functions. For example, trafficked bistable switches can oscillate or become quad- or tristable, depending on trafficking mechanisms and rates. Furthermore, the analysis shows how compartments participating in traffic can settle to distinct molecular compositions characteristic of distinct organelle identities. This general framework shows how the interplay between molecular movement and local reactions can generate many system functions, and give distinct identities to different parts of the cell.
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Affiliation(s)
- Upinder Singh Bhalla
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India.
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14
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Abstract
BACKGROUND Recent studies have found that overexpression of the High-mobility group box-1 (HMGB1) protein, in conjunction with its receptors for advanced glycation end products (RAGEs) and toll-like receptors (TLRs), is associated with proliferation of various cancer types, including that of the breast and pancreatic. RESULTS We have developed a rule-based model of crosstalk between the HMGB1 signaling pathway and other key cancer signaling pathways. The model has been simulated using both ordinary differential equations (ODEs) and discrete stochastic simulation. We have applied an automated verification technique, Statistical Model Checking, to validate interesting temporal properties of our model. CONCLUSIONS Our simulations show that, if HMGB1 is overexpressed, then the oncoproteins CyclinD/E, which regulate cell proliferation, are overexpressed, while tumor suppressor proteins that regulate cell apoptosis (programmed cell death), such as p53, are repressed. Discrete, stochastic simulations show that p53 and MDM2 oscillations continue even after 10 hours, as observed by experiments. This property is not exhibited by the deterministic ODE simulation, for the chosen parameters. Moreover, the models also predict that mutations of RAS, ARF and P21 in the context of HMGB1 signaling can influence the cancer cell's fate - apoptosis or survival - through the crosstalk of different pathways.
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15
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Conserved molecular mechanisms underlying homeostasis of the Golgi complex. Int J Cell Biol 2010; 2010:758230. [PMID: 20976261 PMCID: PMC2952910 DOI: 10.1155/2010/758230] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2010] [Revised: 07/30/2010] [Accepted: 08/19/2010] [Indexed: 01/16/2023] Open
Abstract
The Golgi complex performs a central function in the secretory pathway in the sorting and sequential processing of a large number of proteins destined for other endomembrane organelles, the plasma membrane, or secretion from the cell, in addition to lipid metabolism and signaling. The Golgi apparatus can be regarded as a self-organizing system that maintains a relatively stable morphofunctional organization in the face of an enormous flux of lipids and proteins. A large number of the molecular players that operate in these processes have been identified, their functions and interactions defined, but there is still debate about many aspects that regulate protein trafficking and, in particular, the maintenance of these highly dynamic structures and processes. Here, we consider how an evolutionarily conserved underlying mechanism based on retrograde trafficking that uses lipids, COPI, SNAREs, and tethers could maintain such a homeodynamic system.
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16
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Abstract
Newly synthesized secretory cargo molecules pass through the Golgi apparatus while resident Golgi proteins remain in the organelle. However, the pathways of membrane traffic within the Golgi are still uncertain. Most of the available data can be accommodated by the cisternal maturation model, which postulates that Golgi cisternae form de novo, carry secretory cargoes forward and ultimately disappear. The entry face of the Golgi receives material that has been exported from transitional endoplasmic reticulum sites, and the exit face of the Golgi is intimately connected with endocytic compartments. These conserved features are enhanced by cell-type-specific elaborations such as tubular connections between mammalian Golgi cisternae. Key mechanistic questions remain about the formation and maturation of Golgi cisternae, the recycling of resident Golgi proteins, the origins of Golgi compartmental identity, the establishment of Golgi architecture, and the roles of Golgi structural elements in membrane traffic.
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Affiliation(s)
- Benjamin S Glick
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA.
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17
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Gong H, Guo Y, Linstedt A, Schwartz R. Discrete, continuous, and stochastic models of protein sorting in the Golgi apparatus. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:011914. [PMID: 20365406 PMCID: PMC5367640 DOI: 10.1103/physreve.81.011914] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 10/26/2009] [Indexed: 05/29/2023]
Abstract
The Golgi apparatus plays a central role in processing and sorting proteins and lipids in eukaryotic cells. Golgi compartments constantly exchange material with each other and with other cellular components, allowing them to maintain and reform distinct identities despite dramatic changes in structure and size during cell division, development, and osmotic stress. We have developed three minimal models of membrane and protein exchange in the Golgi-a discrete, stochastic model, a continuous ordinary differential equation model, and a continuous stochastic differential equation model-each based on two fundamental mechanisms: vesicle-coat-mediated selective concentration of cargoes and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins during vesicle formation and SNARE-mediated selective fusion of vesicles. By exploring where the models differ, we hope to discover whether the discrete, stochastic nature of vesicle-mediated transport is likely to have appreciable functional consequences for the Golgi. All three models show similar ability to restore and maintain distinct identities over broad parameter ranges. They diverge, however, in conditions corresponding to collapse and reassembly of the Golgi. The results suggest that a continuum model provides a good description of Golgi maintenance but that considering the discrete nature of vesicle-based traffic is important to understanding assembly and disassembly of the Golgi. Experimental analysis validates a prediction of the models that altering guanine nucleotide exchange factor expression levels will modulate Golgi size.
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Affiliation(s)
- Haijun Gong
- Department of Physics, Carnegie Mellon University, Pennsylvania 15213, USA
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